2005 - 2006

Tomato Research ReportSupported by the Florida Tomato Committee

An Equal Opportunity Institution

Office of the Dean for Research 1022 McCarty Hall/PO Box 110200 Florida Agricultural Experiment Station Gainesville, FL 32611-0200

Phone: (352) 392-1784 / Fax: (352) 392-4965E-mail: research@ifas.ufl.edu

Website: http://research.ifas.ufl.edu

MEMORANDUM

TO: The Florida Tomato Committee

FROM: George J. Hochmuth, Associate Dean for Research

SUBJECT: 2005-2006 Research Report

DATE: September 6, 2006

This report describes research in UF/IFAS/FAES that received support from the FloridaTomato Committee during the past year. The Florida Tomato Committee supportcombines with State and Federal resources to allow IFAS tomato scientists to have astrong and productive research program focused on the tomato industry of Florida.

This is an extremely important partnership between the Tomato Industry and IFASscientists. We have worked together to identify the questions and needs for the industry.Then, again together we have prioritized the research to be accomplished. This year’swork ranged from tomato breeding to methyl bromide alternatives to economics,competitiveness and trade issues. Many of the results are immediately applicable by theindustry.

We hope to continue in our quest for improving production methods and product quality.We are pleased to have the Florida Tomato Committee as a partner in programmaticsupport for tomato research. On behalf of the scientists involved in tomato research, wethank you and appreciate your support.

This report of research results is presented in electronic format. We hope you find theinformation in the report useful to all facets of tomato production.

GJH:las

cc: Mark McLellan

INDEX

FLORIDA TOMATO COMMITTEE

2005-2006 IFAS Research Reports

Page Title Investigator(s)

FOOD SAFETY AND HANDLING

1 Conditions Affecting Bacterial Contamination of Tomatoes Keith Schneider

R. M. Goodrich

Jerry A. Bartz

Hyun-Gyun Yuk

10 Technical and Cost/Benefit Analysis of Self-Propelled Harvest

Aids for Increased Labor Efficiencies and Postharvest Quality

Steven A. Sargent

John J. VanSickle

Santiago Bucaram

17 Sanitation options for tomatoes Jerry A. Bartz

Keith Schneider

Steven A. Sargent

TOMATO BREEDING

30 Breeding Tomatoes for Florida John W. Scott

Waldy Klassen

36 Breeding Tomatoes for Resistance to all Races of the Bacterial

Spot Pathogen

John W. Scott

Jeffrey B. Jones

41 Continued Evaluation of Tomato Lines that Exhibit a Fruity/Floral

Flavor Character within a Balanced Sugar, Acid and Volatile Profile

for Development of a Premium Commercial Variety

Elizabeth A. Baldwin

John W. Scott

45 TYLCV-resistant Tomato Cultivar Trial and Whitefly Control Kent Cushman

Philip Stansly

OTHER TOPICS

57 Agar Media and Laboratory Methods for Detection and Evaluation

of Copper Resistance Among Bacterial Pathogens of Vegetables in

Florida and Disease Control in the Greenhouse

Ken Pernezny

Russell Nagata

Nikol Havranek

Jairo Sanchez

70 Characterization of the Phytophthora infestans population present

in Florida

Pamela Roberts

Diana Schultz

Charles Mellinger

75 Evaluating Factors Affecting Movement of the Silverleaf Whitefly

and Tomato Yellow Leaf Curl Virus

David J. Schuster

Jane E. Polston

Sabrine Grunwald

77Implications of a Change in Carton Size for Fresh Tomatoes from

25 pounds to 10 Kilograms

John J. VanSickle

Evan Shinbaum

1

Conditions Affecting Bacterial

Contamination of Tomatoes

Investigators

Keith R. Schneider, Food Science and Human

Nutrition Dept., Gainesville, FL

Renée M. Goodrich, CREC, Lake Alfred, FL

Jerry A. Bartz, Plant Pathology Department,

Gainesville, FL

Hyun-Gyun Yuk, Post Doctoral Research

Associate, FSHN, Gainesville, FL

Abstract. Salmonella have been identified as a

causative agent of several outbreaks associated

with the consumption of raw tomatoes since

1990. Although there are many routes for the

infection of Salmonella on/in tomato during

growing, harvesting, post-harvesting, and

storage, the infiltration (or internalization) of

this pathogen into tomato fruit may be one cause

of outbreaks. Infiltration of Salmonella into

tomato fruit may protect the bacterium from

disinfecting solutions in the dump tank and also

increase the availability of nutrients. In addition,

several studies indicated that Salmonella on the

surface of tomato could not survive under

controlled certain conditions.

This study continued to examine the conditions

that support growth of Salmonella on tomato

surfaces. In addition, studies were performed to

determine the extent of infiltration of

Salmonella on tomato smooth surfaces, puncture

wounds and stem scares.

Introduction. Salmonella is a second leading

foodborne pathogen and accounts for an

estimated 1.5 million cases of foodborne illness,

causing 16,430 hospitalizations and 582 deaths,

in the United States annually (Mead et al.,

1999). This pathogen has been originally

associated the consumption of animal originated

foods such as poultry, egg, and meat; however,

recent outbreaks indicate that tomatoes may act

a vector of Salmonella since 1990 (Wood et al.,

1991). Salmonella that contaminate intact,

smooth surfaces of tomatoes can be easily

removed through standard cleaning or chlorine

treatments. However, microbes in corky or

wounded areas are much more resilient (Wei et

al., 1995; Zhuang et al., 1995). Moreover,

pathogens internalized (embedded in tomato

tissues) are protected from contact with biocidal

treatments and adverse environments; treatment

of tomatoes with chlorine after exposure to

inoculum did not prevent decay. Understanding

mechanisms of this infiltration, such as timing

and conditions which it occurs, can be helpful

for future recommendations of handling,

processing and sanitation to avoid further

human illness and perhaps also reduce loss due

to postharvest contamination. Although many

fruits may serve as vehicles of Salmonella and

the environmental conditions that promote

infiltration during postharvest handling are

likely to occur, this review will deal with

tomatoes as a vehicle of Salmonella including

outbreak history and the mechanism of

infiltration in dump tanks during postharvest

handling.

Salmonella outbreaks linked to

fresh tomatoes

Tomato-associated Salmonella outbreaks

reported to Centers for Disease Control and

Prevention (CDC) have increased in frequency

and magnitude in recent years and caused 1,616

reported illnesses in nine outbreaks during

1990-2004, representing approximately 60,000

illnesses.

Disinfection of tomato and survival

of Salmonella

Tomatoes can become contaminated with

Salmonella through contact with animal excreta

(bird, insect, rodent and reptile), contaminated

soil, infected water (irrigation or rain),

improperly composted manures used as

fertilizers during growing and harvesting

seasons, or through infected workers (Wei et al.,

1995). Tomatoes are currently sanitized using

chlorinated water prior to shipping to control

postharvest decay or contamination by

pathogenic bacteria. Tomatoes are dumped into

flume tanks containing 150 to 200 ppm of free

chlorine at 10°C, typically at pH 6.5 to 7, for a

short period of time before being packed (Bartz

et al., 2001).

2

Several studies showed the chlorine efficacy for

inactivating Salmonella spp. on whole tomatoes

as well as stem scars and wounds. Wei et al.

(1995) inoculated S. Montevideo on whole

tomatoes and stem scar. Dipping with 100 ppm

chlorine for up to 2 minutes at room temperature

failed to completely kill cells on tomato skin

and stem scar, surviving more than 1.7-log

units. Zhuang et al. (1995) reported that dipping

of tomatoes in 320 ppm chlorine (25°C) for 2

minutes decreased S. Montevideo cell numbers

by about 1.5 and 1.0-log units on the surface

and stem scar, respectively, but did not

completely eradicate the cells. Weissinger et al.

(2000) treated tomatoes inoculated with S.

Baildon by dipping the whole tomato in 120 and

200 ppm of chlorine for 40 sec. Tomatoes were

still positive for Salmonella after the 200 ppm

treatment and populations with both treatments

were reduced by less than a 1.0 log cfu/ml. In

contrast, Felkey (2002) reported that 150 ppm

free chlorine treatment for 120 sec at pH 6.5 and

35°C reduced 4.9-log of Salmonella spp., while

there were only 1.0- and 0.7-log reductions on

stem scar and in wound of tomatoes,

respectively. Under the same treatment

conditions as the Felkey study, Yuk et al. (2004)

tested the chlorine efficacy at 200 ppm level for

inactivating Salmonella spp. before and after 5-

day storage at 20°C and 95% relative humidity.

Chlorine treatment for tomatoes inoculated on

smooth surface showed more than 5.0-log

reduction in the number of Salmonella cells

relative to unsanitized controls and no cells

were detected after 5-day storage, whereas

reductions were 2.5- and 1.3-log units for stem

scar and wounds of tomatoes, respectively.

These investigations suggested that chlorine can

eliminate Salmonella easier on smooth surfaces

than in stem scar and puncture wounds of

tomatoes. In addition, chorine efficacy varied by

concentration of chlorine, pH, and temperature.

Although chlorine treatment fails to eliminate

Salmonella on the surfaces of tomatoes in dump

tanks, some previous reports noted that cells

could not survive on smooth surfaces during

storage. Guo et al. (2002) reported a 4.0-log unit

reduction in inoculated Salmonella populations

on mature, green tomatoes over 14-day at 20ºC

and 70% RH. Allen et al. (2005) showed that a

five-serovar Salmonella cocktail decreased on

tomato surface when stored at 20ºC/60% RH

and 30ºC/90% RH over the 28-d experiment. In

addition, Warren et al. (2006) demonstrated that

Salmonella populations inoculated on tomato

surfaces decreased over 14-day storage at

13°C/85% RH and no survivors were detected

after 19-days. These survival studies, therefore,

suggest that Salmonella on tomato surfaces

could not be a cause of several outbreaks, even

if there was variation of chlorine treatments

among dump tanks or cross-contamination from

chlorinated water. In contrast to smooth tomato

surfaces, the tomato stem scar is a possible

cause of outbreaks, because Salmonella cells

could infiltrate into tomato through stem scar,

thereby protecting cells from chlorine treatment

during post-harvest handling and potentially

allowing the proliferation of cells inside the

tomato.

Objectives. This study will evaluate the

conditions that lead to the infiltration and

survival of Salmonella spp. from tomatoes.

Tomatoes were inoculated with a known amount

of a rifampicin resistant five-serovar Salmonella

cocktail. Salmonella recovery from the surfaces,

as well as areas within the tomato were

examined. Inoculated fruit were subjected to

specific temperatures and harvest combinations.

• Compare dye infiltration vs. bacterial

movement

o This study will examine the

correlation of dye indicators and

Salmonella inoculum.

Preliminary studies have shown

that the inoculum and surrogate

dyes can penetrate the same areas

of a tomato, though initial

indications are that each can take

their path. In this experiment,

alternative methods of tracking

fluid movement were studied.

3

• Examine conditions that enhance

infiltration and survival

o Time after harvest, as well as

weather conditions have been

discussed as possible factors in

the susceptibility to bacterial

infection. This study will

examine the ability of Salmonella

to infiltrate tomato at the stem

scar area. Bacterial cultures were

introduced at predetermined time

intervals post stem removal to

evaluate the risk of infection. In

addition to bacterial infiltration,

this study will examine the water

uptake of tomato before and after

stem removal to assess the risk

associated with harvesting

conditions.

Materials and Methods.

Salmonella cultures

All Salmonella cultures were obtained from Dr.

L.J. Harris at the University of California,

Davis. The serovars used in this study were S.

Agona LJH618 (alfalfa sprouts isolate), S.

Gaminara LJH616 (orange juice isolate), S.

Michigan LJH615 (cantaloupe isolate), S.

Montevideo LJH614 (human isolate from

tomato outbreak) and S. Poona LJH631 (human

isolate from tomato outbreak).

Salmonella survival study

Tomatoes were placed in sterile fiberglass trays

with the blossom scar faced up. Smooth surfaces

around the blossom scar of tomatoes were spot

inoculated at 10 sites per fruit with 10 l per site

using appropriate dilutions to obtain final

inoculation levels of approximately 5.0 x 105

most probable number (MPN)/tomato with five

replicate tomatoes at each level. The inoculated

tomatoes were dried for at least 1 h in a laminar

flow hood at room temperature. After drying,

tomatoes were stored in humidity chamber at

13ºC with 85% RH and five inoculated

tomatoes were transferred to sterile Stomacher®

bags (Seward, Norfolk, UK) containing 100 ml

of sterile phosphate buffered saline (PBS; pH

7.4) at each observation day. For recovery of

inocula, tomatoes were shaken vigorously for 30

s, then massaged by hand for 1 min in the

Stomacher® bag similar to that described by

Zhuang et al. (1995).

Salmonella infiltration study

A 100- l aliquot of a five-serovar Salmonella

cocktail was inoculated in the stem scar of

tomato. The inoculum was allowed to air dry for

approximately one hr before testing. With a

flame sterilized sharp knife, tomatoes received

two cuts, resulting in three pieces (Figure 3).

Images of the cut surfaces were taken using a

digital camera. The knife was cleaned and

sterilized with flame between each cut to

prevent cross-contamination. The cut surfaces

were stamped on to the surface of inverted TSA

rif+ plates and incubated at 37°C for 24 hr.

Photographic overlays consisted of images of

growth on plates after 24-hr incubation with an

image of the corresponding tomato segment

using computer graphic software (Adobe

Photoshop® 7.0, Adobe System Inc. San Jose,

CA). These overlaid images were set to ~50%

transparency to allow correlation of bacterial

colonies with location of recovery from fruit.

For each sample, two separate composite

images were made; the section created by the

vertical AB slice and the section created by the

longitudinal CD slice (Figure 3)

Recording of data and statistical analysis. All

statistical analyses were performed using the

Statview statistical software package version 9.1

(SAS Institute Inc., Cary, NC) using a mixed

model. Sample replications were treated as

random variables within time. A P value < 0.05

was considered as a significant difference for all

experiments.

Results and Discussion.

Salmonella survival study

Survival studies showed an initial population of

Salmonella of 5.8 log MPN/g (Figure 1). To

evaluate the effect of drying each inocula

cocktail on the surface of the tomatoes,

populations were enumerated immediately after

4

inoculation and at 90 min after inoculation (time

for inocula to be completely dry on all

tomatoes). Drying of the inocula on tomato

surfaces resulted in a significant (P < 0.05)

reduction of Salmonella compared to initial

populations (4.0 log MPN/tomato).

Significant decreases (P < 0.05) in Salmonella

populations were observed on days 1, 3 and 14,

indicating that Salmonella which survived the

drying process continued to decline after drying

(Figure 1). No survivors (detection limit of the

assay was < 3 MPN/tomato) were detected on

days 19 and 28. After a few days at 13°C/85%

RH, several tomatoes inoculated with

Salmonella developed a white mold at the stem

scar. Between days 19 and 28, tomatoes began

to develop orange color and several developed

mold lesions on the smooth surfaces in addition

to the stem scar.

Figure 2 shows the survival of Salmonella spp.

inoculated on smooth surface and in puncture

wounds. Significant decreases (P < 0.05) in

Salmonella populations on smooth surface of

tomatoes were observed during 14-day storage

in humidity chamber at 20°C/60% RH. At day

10 and 14, survivors decreased to detection limit

(detection limit of the assay was 2.0 log

CFU/tomato). In contrast, there was a

significant increase (P < 0.05) on the population

of Salmonella spp inoculate in puncture wounds

of tomatoes during 14-day storage.

Approximately 1.5-log unit increase at day 1

was maintained to day 14 with no significant

difference (P > 0.05).

Salmonella infiltration study

Figure 3 shows the cutting patterned used to

determine Salmonella infiltration. The removal

of a 1 cm slice was used to eliminate the

possibility of contamination caused by the

cutting process. In previous studies, results

indicated that Salmonella could infiltration to a

depth greater than 1 cm (data not shown).

Figure 4 shows the movement of dye into the

surface of a puncture wound. Previous work

has shown that dye placed onto the stem scar

could penetrate throughout the tomato alone the

vascular system of the tomato. This study

attempted to assess if the inoculated bacteria

moved along with the dye front. As seen in

Figure 5, no bacterial infiltration was seen a

depth of greater than 1cm. Only one sample out

of a total of 30 tested (stem scar inoculated)

resulted in Salmonella penetration (data not

shown).

Summary. The results of this study emphasis

the risk of Salmonella associated with tomatoes.

Results showed that Salmonella can survival for

extended periods of time under standard storage

conditions. The presence of a wound on the

tomato surface resulted in an environment

conducive to Salmonella survival and growth.

An examination of dye movement as compared

to bacterial internalization showed that the dye

penetrated to a further depth as compare to the

Salmonella. The most penetration was observed

in the stem scar.

5

Literature Cited

Allen, R. L. B. R. Warren, D. L. Archer, S. A.

Sargent, and K. R. Schneider. 2005. Survival of

Salmonella spp. on the surfaces of fresh

tomatoes and selected packing line materials.

HortTech. 15:831-836.

Bartz, J.A., C.G. Eayre, M.J. Mahovic, D.E.

Concelmo, J.K. Brecht, and S.A. Sargent. 2001.

Chlorine concentration and the inoculation of

tomato fruit in packinghouse dump tanks. Plant

Dis. 85: 885-889.

Felkey KD. 2002. Optimization of chlorine

treatments and the effects on survival of

Salmonella spp. on tomato surfaces. M.S.

Thesis, University of Florida, Gainesville, FL.

Mead, P. S., L. Slutsker, V. Dietz, L. F.

McCaig, J. S. Bresee, C. Shapiro, P. M. Griffin,

and R.V. Tauxe. 1999. Food-related illness and

death in the United States. Emerg. Infect. Dis.

5:607-625.

Warren B. R., H. G. Yuk, and K. R. Schneider.

2006. Survival of Salmonella spp. and Shigella

sonnei in gorund beef, potato salad and on

tomato surfaces. submitted to J. Food Prot.

Wei C. I., T. S. Huang, J. M. Kim, W. F. Lin,

M. L. Tamplin, J. A. Bartz. 1995. Growth and

survival of Salmonella Montevideo on tomatoes

and disinfection with chlorinated water. J. Food

Prot. 58:829-36.

Wood, R.C., C. Hedberg, and K. White. 1991. A

multi-state outbreak of Salmonella javiana

infections associated with raw tomatoes

(Abstract), p. 69. In CDC Epidemic Intelligence

Service 40th

Annual Conference. Atlanta: U.S.

Department of Health and Human Services,

Public Health Service.

Weissinger, W.R., W. Chantarapanont, and L.R.

Beuchat. 2000. Survival and growth of

Salmonella baildon in shredded lettuce and

diced tomatoes, and effectiveness of

chlorinated water as a sanitizer. Int. J. Food

Microbiol. 62 (1-2):123-131.

Yuk H-G, Bartz JA, Schneider KR. 2004.

Effectiveness of individual or combined

sanitizer treatments for inactivating Salmonella

spp. on smooth surface, stem scar, and wounds

of tomatoes. J Food Sci 70:M409-414.

Zhuang, R. Y., L. R. Beuchat, and F. J. Angulo.

1995. Fate of Salmonella Montevideo on and in

raw tomatoes as affected by temperature and

treatment with chlorine. Appl. Environ.

Microbiol. 61:2127-2131.

6

Figure 1: Survival of a 5-serovar Salmonella cocktail artificially inoculated on tomato surfaces. Each

Salmonella was resistance to 100 ppm rifampicin by spontaneous adaptation. Inoculated tomatoes were

stored at 13°C and 85% relative humidity. Inocula were recovered by placing each tomato into a sterile

Somacher® bag containing 100 ml phosphate buffered saline and shaking vigorously for 30 s followed

by a 1 min hand massage. Five replicate tomatoes were sampled at each time point. Survivors were

enumerated using a 3-tube most probable number method in tryptic soy broth supplemented with 100

ppm rifampicin.

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0 5 10 15

Day

Su

rviv

ors

log

MP

N/t

om

ato

7

Figure 2: Survival of a five-serovar Salmonella cocktail artificially inoculated on smooth surface and

puncture wounds of tomatoes for 14 days at 20°C and 60% RH.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

0 2 4 6 8 10 12 14 16

Storage time (Days)

Su

rviv

ors

(lo

g C

FU

/to

mato

)

Surface Punctured

8

Figure 3: Diagram of cutting pattern used in infiltration studies. The first cut was made by cutting along

a line in the direction of A to B, resulting in one cm slice (AB slice). A second cut was made by cutting

along a line in the direction of C to D (CD slice); cutting in the direction towards the inoculation site, to

prevent inadvertently moving cells further into the fruit. The inoculation site is represented by .

Figure 4: Dye infiltration in puncture wounds on the surface of tomatoes.

Experimental Method

A

B

CD

1.0 cm

9

Figure 5: Images of infiltrated tomatoes overlaid with the images of bacterial growth on TSA plates

pressed against the tomato surface. Images are of etched tomatoes only. Day 1-AB slice (A); Day 1-CD

slice (B); Day 14-AB slice (C) and Day 14-CD slice (D).

.

(A) (B)

(C) (D)

10

Technical and Cost/Benefit Analysis of Self-

Propelled Harvest Aids for Increased Labor

Efficiencies and Postharvest Quality

Steven A. Sargent1, John J. VanSickle2 and Santiago

Bucaram2

1 Horticultural Sciences Department, P.O. Box

1106902 Food & Resource Economics Department, P.O.

Box 110240

University of Florida, Gainesville FL 32611

Abstract. The previously funded study (Sargent,

2003) concluded that there are a several types of

self-propelled, harvest aid systems available that

could reduce harvest time up to 50%. These

systems also have other efficiencies, including

presorting in the field, reducing the amount of out-

of-grade tomatoes shipped to the packinghouse.

If such a system were implemented, we

conservatively assumed savings in harvest costs of

10% or 20% to account for fixed and variable costs

of the equipment. A sensitivity analysis was

conducted to determine the effects reduced harvest

costs on the competitiveness of Florida tomato

growers with growers in other major tomato

producing areas. The analysis projected that Florida

tomato growers would be much more competitive

than other growing regions if harvest costs were

lowered by 10% or 20% due to the implementation

of a conveyor harvest system. Growers in the

Palmetto-Ruskin district would benefit most

through increased market share, following by

growers in Dade district. There would be minimal

impact on growers in California, while Mexican

growers in Sinaloa state would be most negatively

affected. Further studies will focus on examining

the cost structure for implementing three types of

these conveyor systems.

Introduction. Tomatoes are the largest vegetable

crop grown in Florida, accounting for almost 1/3 of

the total value sold. In the 2004 and 2005 seasons,

tomatoes were harvested from 42,000 acres and

were worth $500 million and $805 million,

respectively USDA NASS, 2006.). However,

tomato production costs continue to increase,

averaging $11,600/acre, up by almost 40% from

2001 (FTC, 2006; Maynard and Olson, 2001).

Therefore, our growers are continually seeking

ways to reduce those costs. The harvest operation

accounts for about 30% of total production costs

and therefore amounts to about $167 million for

Florida growers. Reducing net harvest costs by

only 10% would translate to about $17 million

annual savings for the industry.

In a 2003 study funded by the Florida Tomato

Committee, Sargent identified several commercially

available continuous, harvest-aid systems that

utilize one or two conveyors; the harvest crew

walks behind the unit. There are three general types

of systems, a tractor-mounted system, a self-

propelled conveyor belt system and a mobile field-

packing unit. With each of these systems the crop

is harvested into field buckets and carried to the

conveyor.

The tractor-mounted system is designed for smaller

operations. The single conveyor swings out from

the side of the tractor, and the crop is conveyed

over the tractor and loaded into bins or a gondola.

The self-propelled conveyor belt system is powered

by an on-board diesel engine and moves ahead of

the picking crew and may cover 18 rows. Tomatoes

are moved to the side, pass over undersize

eliminator belts, are sorted and elevated into bins or

a gondola. The mobile field-packing unit is also self-

propelled and has two, swing-out conveyors that

bring the product to the central unit, where it is

graded, packed and palletized. It is intermediate in

size.

We conducted timing studies and found that harvest

was more efficient with the conveyor systems than

with the current harvest system because the crews

required less time to dump the buckets and return

11

to the place where they were picking. We timed

individual pickers with the self-propelled conveyor

belt system and found that it required from 100 to

120 seconds to harvest a bucket, walk to the

conveyor, and return to the picking location. With a

conventional operation, pickers required from 147

to 181 seconds for these operations. Comparing

these values, harvest time potentially could be

shortened up to 50% using the continuous harvest

system, significantly reducing costs for three

postharvest operations: harvest labor,

transportation to the packinghouse and packing

operations. Transportation to the packinghouse

would become more efficient due to the capability

for presorting in the field, thereby reducing the

amount of out-of-grade tomatoes shipped to the

packinghouse. With fewer out-of-grade tomatoes

hauled to the packinghouse, less labor would be

required for sorting and grading, and fewer culls

would require disposal.

The first step in analyzing this system was to

perform a sensitivity analysis to determine how

reduction in harvest costs would impact market

share, production, acreage and revenues for major

tomato growing areas shipping to east coast

markets. These results are presented in this paper.

Methodology. Although 30% to 40% reductions in

harvest labor have been reported by companies

using harvest aids, we selected reductions of 10%

and 20% for this analysis to account for added

capital and operating costs of the new harvest aid.

For this analysis the model of “North American

Vegetable Market” was used in order to estimate

the impacts of increments on efficiency in the

harvesting and packing of fresh tomatoes. This

model, developed by VanSickle (2000), was built in

order to calculate the impacts of a ban of methyl

bromide on producers and consumers of fresh

vegetables in North America. At the same time, this

model was based on the inverse demand system for

the fresh vegetable market developed by Scott

(1991). Later on, Nalampang (2004) expanded these

models and refined the process which was utilized

in this current study.

This model can be defined as a spatial equilibrium

model and is limited to a group of crops: tomatoes,

peppers, eggplant, cucumbers, squash, watermelons

and strawberries. In this report only data for

tomatoes are reported. The following producing

areas were chosen for the model: Florida, Mexico,

California, South Carolina, Virginia and Maryland

combined, and Alabama and Tennessee combined.

Florida was separated into four producing areas:

Dade County, Palm Beach County, Southwest

Florida, and the Palmetto/Ruskin area (West

Central Florida). California was divided in Southern

California (Orange, Ventura, San Diego and Los

Angeles counties) and Northern California. Two

Mexican production areas were also included,

Sinaloa and Baja California. Growing seasons were

analyzed based on one crop for Dade and Mexico

(late fall to early spring) and California (summer).

Spring and fall crops were analyzed for the other

three Florida production areas.

The US vegetable model allocates production of

these crops across regions based on their delivery

costs to regional markets, productivity and the

regional demand structure. As previously stated

for this work, a system of inverse demand

equations was used, based upon work by Scott

(1991). A Rotterdam model was also implemented.

This model is derived from the problem of a

consumer that is maximizing a utility function u(q)

subject to a budget constraint p’ q = m, where m is

total expenditure (or full income), p is a price vector

and q a vector of goods. In this specific case the

model is composed of five equations of fresh

vegetable demand in the US, estimated for four

selected markets: Los Angeles, Chicago, Atlanta

and New York City.

In order to analyze the impact of increased

efficiency in harvesting of fresh tomatoes and the

12

associated costs, the year 2002 was used as a

baseline. Proportional changes in the harvest costs

were applied at a level of -10% and -20% because

of increments in the harvest efficiency. For this

analysis other variables were maintained constant

so as to isolate the system from other phenomena,

such as natural disasters, sharply increased energy

prices and demand reallocation.

We optimized this equation system by a process

through which the optimal reallocation of

production was provided. This was executed using

GAMS program software so as to determine the

impact of this technology and its consequent

contraction on the harvest costs for the production

system. Also, acres devoted to production of fresh

tomatoes in the Dade area were upper-constrained

to acres shown in the baseline, following the

suggestion by growers that acreage available to

tomato production in that county is constrained by

urbanization, water restrictions and labor

availability.

Results and Discussion. Overall, the analyses

showed that decreasing harvest costs by 10% or

20% would give Florida growers a competitive

advantage over other major growing areas. Growers

in Mexico would have substantial losses in market

share, production, acreage and revenues, while

California growers would benefit slightly.

Average Market Share. Results showed that for a

10% decrease in costs, average market share (MS)

would increase for growers in Dade,

Palmetto/Ruskin, Southwest and Palm Beach

districts by 1.6%, 3.6%, 0.4% and 0.2%,

respectively (Table 1). A 20% decrease in costs

would roughly double the increase in MS for

growers in these districts, with the exception for

Palm Beach district which would decrease by 0.2%.

Growers in southern and northern California and in

Baja California, Mexico, would maintain current

MS, while growers in Sonora, Mexico, would lose

5.4% and 11.4% MS for 10% and 20% lower costs,

respectively.

Total Production. Florida production was analyzed

by growing season (single crop, fall, spring) and by

production district. Growers in Palmetto/Ruskin

(fall, spring crops) would benefit most from lower

harvest costs, with the spring crop increasing about

two times that of the fall crop for each reduction in

harvest costs (Table 2A). Production for the single

crop in Dade would increase by 60.5% and 121.8%

for 10% and 20% reductions in harvest costs,

respectively. Southwest growers would lose 32.8%

production for the spring crop with a 10% decrease

in costs, and 8.3% with a 20% decrease, but no

effect on the fall crop. There were no changes for

Palm Beach area growers.

Interestingly, while production in the Sinaloa area

would decrease significantly (64.1% and 26.0%),

production in the smaller Baja California area would

increase by 116.7% for 10% but decrease by 38.5%

for 20% lower harvest costs in Florida (Table 2B).

Although a small production area, Alabama-

Tennessee growers could lose about 40%

production and acreage with a 10% decrease in

Florida production costs, but could realize a

244.5% increase with a 20% decrease. Production

in South Carolina and Virginia-Maryland would

decrease. Production in both California areas would

increase 6.8% with a 20% reduction in costs,

whereas total Mexican production would decrease

by 49.1% and 27.0%, for respective reduced costs

of 10% and 20% (Table 2C).

Acreage. Changes in acreage are projected to be

virtually identical with those for total production.

Revenues. Florida has the largest share of revenue

($925 million) of all of the areas in this study,

followed by California ($246 million) and Mexico

($712 million) (Table 3). With a 10% or 20%

decrease in harvest costs, statewide revenues could

be expected to increase by 7.6% and 14.8%,

respectively; the Dade and Palmetto-Ruskin areas

13

would benefit most, with increases ranging from

13.0% to 38.2%.

For the other production areas, there would be

minimal impacts on revenues for California, while a

20% decrease in costs would have a slightly

negative impact for South Carolina (4.3%), and

moderately negative impacts for Mexico (18.7%)

and Virginia-Maryland (25.4%). Again, Alabama-

Tennessee would see an increase in revenues of

244.5%.

References

Florida Tomato Committee. Orlando, Florida.

http://www.floridatomatoes.org/ (accessed July

2006)

NaLampang, S. 2004. Impact of selected regulatory

policies on the U.S. fruit and vegetable industry.

Unpublished Ph.D. dissertation. Food & Resource

Economics Department, University of Florida,

Gainesville.

Olson, S.M., D.N. Maynard, G.J. Hochmuth, C.S.

Vavrina, W.M. Stall, T.A. Kucharek, S.EE. Webb,

T.G. Taylor, S.A. Smith and E.H. Simonne. Ch.41.

In, Olson, S.M. and E.H. Simonne (eds.), Vegetable

Production Handbook for Florida – 2004-

2005.University of Florida Extension, Gainesville

and Citrus & Vegetable Magazine, Tampa.

Sargent, S.A. 2003. Evaluation of Carnegie Mellon

Mechanical Harvest Project from 2000-2001 for

Harvest Assistance Applications for Improved

Worker Efficiencies. Report to Florida Tomato

Committee.

Scott, S. W. 1991. International Competition and

Demand in the United States Fresh Winter

Vegetable Industry. Unpublished M.S. Thesis,

University of Florida, Gainesville.

VanSickle, J.J., C. Brewster, T.H. Spreen. 2000.

Impact of a methyl bromide ban on the U.S.

vegetable industry. Bulletin 333. February. Food

and Resource Economics Department. Gainesville.

14

Table 1. Average market share for selected tomato growing areas as affected by a 10% or 20%

reduction in Florida harvest costs.

Table 2. Projected changes in production and acreage for selected tomato growing areas and seasons as

harvest costs.affected by a 10% or 20% reduction in Florida

A)

Florida Districts CaliforniaReduced

Harvest

CostDade

Palm

Beach

Palmetto/

Ruskin

South-

westSouth North

10% 1.6% 0.2% 3.6% 0.4% -0.4% 0.0%

20% 3.2% -0.2% 7.7% 1.2% 0.3% 0.0%

MexicoReduced

Harvest

Cost

Alab-

Tenn

South

Carolina

Virg-

Maryl.Sinaloa

Baja

Calif.

10% -0.3% 0.0% -0.1% -5.7% 0.5%

20% 1.5% -0.4% -0.6% -11.4% -1.4%

Florida Production Districts California

Total Production

DadePalm

Beach

Palmetto/

Ruskin

South-

westSouth North

One Crop 60.5% 0.0% 0.0% 0.0% 0.4% 0.0%

Fall 0.0% 0.0% 39.7% 0.0% 0.0% 0.0%10%

Spring 0.0% 0.0% 68.5% -32.8% 0.0% 0.0%

One Crop 121.8% 0.0% 0.0% 0.0% 6.8% 0.0%

Fall 0.0% 0.0% 81.2% 0.0% 0.0% 0.0%20%

Spring 0.0% 0.0% 129.0% -8.3% 0.0% 0.0%

Total Acreage

One Crop 60.5% 0.0% 0.0% 0.0% 0.4% 0.0%

Fall 0.0% 0.0% 39.7% 0.0% 0.0% 0.0%10%

Spring 0.0% 0.0% 68.5% -32.8% 0.0% 0.0%

One Crop 121.8% 0.0% 0.0% 0.0% 6.8% 0.0%

Fall 0.0% 0.0% 81.2% 0.0% 0.0% 0.0%20%

Spring 0.0% 0.0% 129.0% -8.3% 0.0% 0.0%

15

B)

C)

Total ProductionAlab-

Tenn

South

Carolina

Virg-

Maryl.Sinaloa

Baja

Calif.

One Crop -40.4% 2.2% -1.9% -64.1% 116.7%

Fall 0.0% 0.0% 0.0% 0.0% 0.0%10%

Spring 0.0% 0.0% 0.0% 0.0% 0.0%

One Crop 244.5% -4.3% -25.4% -26.0% -38.5%

Fall 0.0% 0.0% 0.0% 0.0% 0.0%20%

Spring 0.0% 0.0% 0.0% 0.0% 0.0%

Total Acreage

One Crop -40.4% 2.2% -1.9% -12.6% 18.6%

Fall 0.0% 0.0% 0.0% 0.0% 0.0%10%

Spring 0.0% 0.0% 0.0% 0.0% 0.0%

One Crop 244.5% -4.3% -25.4% -26.0% -38.5%

Fall 0.0% 0.0% 0.0% 0.0% 0.0%20%

Spring 0.0% 0.0% 0.0% 0.0% 0.0%

Total ChangeTotal Production

Florida California Mexico

One Crop 60.5% 0.4% -49.1%

Fall 39.7% 0.0% 0.0%10%

Spring 39.8% 0.0% 0.0%

One Crop 121.8% 6.8% -27.0%

Fall 81.2% 0.0% 0.0%20%

Spring 90.1% 0.0% 0.0%

Total Acreage

One Crop 60.5% 0.4% -10.0%

Fall 39.7% 0.0% 0.0%10%

Spring 40.5% 0.0% 0.0%

One Crop 121.8% 6.8% -27.0%

Fall 81.2% 0.0% 0.0%20%

Spring 91.1% 0.0% 0.0%

16

Table 3. Projected changes in revenues for selected tomato growing areas as affected by a 10% or 20%

reduction in Florida harvest costs.

Baseline

Revenue10% Reduction in Costs 20% Reduction in CostsProduction

Area($1,000) ($1,000) (%) ($1,000) (%)

Florida 925,248 995,393 7.6 1,062,494 14.8

Dade 75,634 90,866 20.1 104,508 38.2

Palm Beach 217,496 221,178 1.7 210,009 -3.4

Palm-Rusk 345,005 389,850 13.0 444,673 28.9

Southwest 287,112 293,499 2.2 303,304 5.6

California 746,952 747,944 0.1 764,296 2.3

Alab-Tenn 11,620 6,926 -40.4 40,029 244.5

South Carolina 75,881 77,540 2.2 72,640 -4.3

Virg-Maryland 37,970 37,261 -1.9 28,317 -25.4

Mexico 711,938 663,737 -6.8 578,913 -18.7

17

Sanitation Options for Tomatoes

J. A. Bartz, Keith Schneider and Steve

Sargent; Departments of Plant Pathol-

ogy, Food Science and Human Nutrition

and Horticultural Sciences, respectively.

University of Florida, Gainesville.

Abstract. Chlorine dioxide bas has been

used for sanitation of various fruits and

vegetables as well as of inert surfaces.

Most reports involve the application of

specified headspace concentrations for

intervals of up to 135 min. At the end of

treatment, the remaining chlorine diox-

ide is purged or dissipated by some other

means. We’ve used a mixture of dry

materials or an aqueous solution of chlo-

rine dioxide gas to supply gas to wound-

inoculated tomato fruit. We used poly-

carbonate chambers containing KI solu-

tions as sinks and aqueous solutions of

chlorine dioxide as sources to model to-

mato treatment. With an initial dose of 6

mg of chlorine dioxide in 30 ml of wa-

ter, about 75% of the chlorine dioxide

off-gassed within the first 2 h and 75%

of this was captured in the sink indicat-

ing that very little was left in the head-

space. The control of bacterial soft rot in

wound inoculated fruit by application of

chlorine dioxide gas during a 2 or 24-h

treatment was based on the ratio of the

mass of chlorine dioxide applied to the

mass of fruit treated. The headspace

concentrations are not relevant for suc-

cessful treatments. However, the stan-

dard cardboard boxes appear to interfere

with successful treatments.

Introduction. Chlorine dioxide as a gas

has an enormous potential for sanitation

in tomatoes and tomato handling facili-

ties. It can not only clean the fruit sur-

face but also the room in which the fruit

are treated. It has been used to decon-

taminate (anthrax spores) the Hart Sen-

ate Office building and the Brentwood

Postal Office building (Czarneski, and

Poisson, 2005). Its use for sanitizing the

interior of equipment and facilities used

in food preparation has been described.

Experimentally, it has been used to

eliminate human pathogens previously

placed on fresh fruits and vegetables

(Linton, 2006). The treatment interval

typically ranges from 10 to 135 min and

the dose is based on the chamber vol-

ume. At the end of the treatment, the

chamber is purged to remove the re-

maining ClO2. These types of experi-

mental treatments do not appear easily

adapted to fruit or vegetable packing-

houses where large volumes of product

are handled daily.

Dry envelopes containing a powder de-

signed to produce ClO2 in humidified air

have been used to control mold growth

on books in a library (Weaver-Meyers et

al., 1998). Theoretically, the gas was to

be produced over a 15 to 30-day period

(higher production rates at higher hu-

midity) at very low concentrations. This

slow rate of production coupled with a

complete control of mold and spores

suggest that low concentrations of the

gas could cause incremental damage to

the mold until it was destroyed.

We have been examining various appli-

cations of ClO2 gas to tomatoes. We’ve

examined its use for controlling posthar-

vest decay and for eliminating fruit con-

tamination as a food safety treatment.

Two different sources were used, an

aqueous solution or a mixture of dry

materials, which included sodium chlo-

rite and an activator (Linton, 2006).

We’ve been especially interested in es-

tablishing that the gas moves en mass

from a source to the tomatoes, high

18

headspace concentrations aren’t neces-

sary, the dose can be based on the

weight of fruit, and that at the end of the

treatment interval the area around the

fruit is essentially free of unreacted gas.

As such, a treated area would be safe for

workers as soon as the treatment is com-

pleted and the room is opened. For many

experiments we’ve used tomatoes and

for a few we’ve used solutions of potas-

sium iodide, which react with strong

oxidizers upon contact (Blaedel and

Meloche, 1957), as surrogate tomatoes.

These model sinks enable us to accu-

rately measure the amount of ClO2 that

contacts any particular area within

treatment chamber. Additionally, with

use of aqueous solutions we can measure

the delivery of the gas to the chamber

and thus to partition the delivered gas

among the source, sink and headspace.

Materials and Methods. A Lexan poly-

carbonate lid was placed over a 19-L

rectangular polycarbonate bin (Rubber-

maid, Inc.). A DC plastic box fan was

attached to the bottom surface of each

lid to provide air-movement within the

chamber. The power wires were

threaded to a hole cut in the lid (Figure

1). Each hole was sealed and the wires

were connected in parallel to a single

DC power source. Alternatively, an alu-

minum 21-L pressure cooker was modi-

fied by the attachment of a DC plastic

box fan to the bottom surface of the lid

(figure 1). The wires for the fan were

threaded through a rubber plenum that

replaced the safety pressure-release plug.

Duct tape sealed the pressure regulator

stem and the pressure release valve. The

fan wires were connected to the DC

power supply. Production curves from

dry materials were prepared by taping an

activated sachet to a glass jar lid. The

base of the jar was covered with a solu-

tion of potassium iodide. The ClO2 gas

moved from the activated chlorite into

the solution by gravity. The solution was

titrated as described below to describe

amount of gas produced.

Aqueous solutions of ClO2 gas were

produced in deionized water contained

in a flask by the immersion of an

Tyvek® envelope (DuPont Corporation)

containing impregnates of solid chlorite

and an acidic activator (ICA-Trinova

Corporation, LLC (Newnan, Georgia)).

The flask was placed in a refrigerator

and incubated for 24 to 72 h. The re-

sulting aqueous solution stored at 5oC in

a brown, stained-glass bottle with a

ground-glass stopper. Prior to tests, a

sample of the solution was removed and

the ClO2 concentration determined by

titration. For specific treatments, a pi-

pette was used to place a sample of this

stock solution at the bottom of deionized

water in a 150-mm Petri dish. For pro-

duction of ClO2 from dry ingredients,

sodium chlorite flakes were mixed with

an equal weight of a moist zeolite that

was impregnated with ferric chloride.

As a scale model of a tomato fruit, 30 ml

of an aqueous solution of a 10% (wt/wt)

solution of KI was placed in a 150 mm

diameter Petri dish base that was en-

closed in a chamber with a source. The

KI is known to be rapidly oxidized by

strong oxidizers (Blaedel and Meloche,

1957) and, as a consequence would be

considered a strong sink. The amount of

ClO2 in the various solutions was deter-

mined by iodometric titration to a color-

less starch endpoint.

Standard, packed tomato fruit were used

in most tests (the authors gratefully

thank the DiMare Corp for supplying

most of the tomatoes). The fruit were

19

selected for uniformity of color and an

absence of blemishes. Wounds were

made on fruit surfaces by use of a scal-

pel to remove of an approximately 2-cm2

strip of periderm at five areas around the

circumference of each fruit. A sample of

a prepared aqueous cell-suspension of

bacteria was placed on each wound. The

bacterium used for tests on controlling

bacterial soft rot was Erwinia caroto-

vora.

The production of ClO2 from dry ingre-

dients was followed over a 24-h period.

The transfer of ClO2 from an aqueous

source to simulated tomato sink was also

examined for a period of 24 h. An aque-

ous source was used to treat tomato fruit

with different amounts of ClO2 or a sin-

gle dose was applied to increasing

weights of tomato fruit. After treatment

the fruit were stored for up to 5 days at

22 to 24oC and >95% relative humidity.

During this storage, fruit were examined

daily for developing lesions. As a scale-

up test, wound-inoculated fruit were

distributed among three 25-lb boxes of

fruit. The boxes were stacked up and en-

closed with a fan in a black plastic drum

liner. A sachet producing a dose found to

be effective in the chamber tests was

taped to the surface of one of the boxes.

The liner was taped shut and the fan was

started. After 2 h, the fruit were removed

and the inoculated fruit were observed

for decay development. The cardboard

from a standard tomato box was com-

pared with tomato fruit as competing

sinks for ClO2. The amount of each ma-

terial was proportional to their presence

in a standard 25-lb box of fruit. A 10-X

dose ClO2 was applied to tomato fruit

over a period of 24-h to find how the

fruit responded to excessive gas.

Results and Discussion. The majority

of the ClO2 produced from the dry mate-

rials (Fig. 1) occurred in the initial part

of the incubation period (Fig. 1). The

general shape of the production curves

was similar for sachets designed to pro-

duce ClO2 over a 2-h period (not

shown). Within the first 30 min after an

aqueous solution was exposed to fan-

driven air about 30% of the ClO2 was

off-gassed and 50% of this was captured

in a KI sink (Fig. 2). By 60 min, 46%

had off-gassed, and 76% of this had been

captured. By 2 h, these parameters were

78 and 76%, respectively. Thus, very

little ClO2 remained in the headspace.

As the treatment progressed to the 24-h

endpoint, the percentage of the off-

gassed ClO2 that was captured decreased

likely because the I2 produced in the sink

reactions was also off-gassed. Moreover,

the chlorite ion that was a product of

these reactions is, itself a strong oxidizer

and was reacting with the iodide ion.

The final reaction product of chlorite

oxidation is chloride ion (White, 1999).

Neither chlorite ion nor ClO2 is a chlori-

nator unlike the hypochlorite bleaches.

The application of 0.75 or 7.5 mg of

ClO2 to approximately 1.2 kg of wound-

inoculated tomato fruit provided excel-

lent control of bacterial soft rot (Fig. 3).

Decay incidence at 4 days post-treatment

averaged about 10% for the lower dose

and 1-2% for the higher dose. By con-

trast, 90% of the inoculated control fruit

had soft rot lesions. By way of compari-

son, in several tests, washing inoculated

fruit up to 600 ppm at pH 7.0 yielded

disease incidences of 55 to 80% (Bartz,

unpublished). In other comparisons of 2

versus 24-h treatments (not shown here),

the longer treatments were associated

with greater changes in stem scar tissues

that enabled water uptake during fruit

20

exposure to simulated wet dumps and

flumes.

When aqueous solutions were used to

supply ClO2 to fruit at a single dose but

with increasing amounts of fruit or in-

creasing doses with a single weight of

fruit, disease control was affected by the

ratio of fruit weight versus ClO2 applied

(Figs. 4 and 5). Thus, a dose can be

based on the weight of fruit treated. Of

note here is that with 1.2 kg of inocu-

lated fruit plus 5 kg of filler fruit, there

was very little headspace left in the alu-

minum chamber. The ClO2 off-gassed

into very little air space meaning the

headspace concentration, if it existed,

would have been quite high. This didn’t

lead to better control because it was the

total size of the sink that determined ef-

ficacy.

When one to three boxes of fruit were

treated with an established dose (3

mg/kg fruit) up through a dose 16 times

higher (48 mg/kg) decay control was not

at the same level as noted in the chamber

tests (Fig. 7). Possible reasons included

that the cardboard box surfaces reacted

with the ClO2, the gas was not being

distributed through the boxed fruit, or

the drum liner, black polyethylene, was a

large sink. The fruit did not show major

evidence of phytotoxicity, thus poor dis-

tribution was discarded as a reason. The

cardboard was suspected because ClO2

is used by paper mills to bleach wood

pulp in the manufacture of white paper

products. When pieces of a tomato box

were enclosed with the simulated tomato

fruit, much less ClO2 was captured by

the sinks as compared with aluminum

foil, Plexiglas, or drum liner material

(Fig. 8). Furthermore, the box material

was a stronger sink than either wounded

or non-wounded fruit (Fig. 9). Prelimi-

nary tests on use of a forced-air delivery

of ClO2 to a standard 25-lb box of to-

matoes appear promising and are con-

tinuing. Additionally, we are testing

coated box materials to find if the coat-

ing limits the reaction between the paper

and the ClO2.

The application of a 10_ dose (20

mg/kg) within a 2-h period produced a

bleaching and necrosis of stem scar tis-

sues (Fig. 10). There was no evident

damage to the waxy surface of the fruit

although fruit ripening occurred earlier

with the high dose and mold eventually

grew on the damaged tissues (Mahovic

et al, 2006). The chlorite residues on the

fruit as a result of the 10_ dose were at

or below the detection minimum (un-

published data). Thus, the gas treatment

should not incur problems with registra-

tion.

Literature Cited:

Bartz, J. A., Mahovic, M. and Tenney, J.

2005. Chlorine dioxide as a postharvest

sanitizer: reversible and irreversible

sinks. (abstr.) Phytopathology 95:S7:7-

7.

Blaedel, W. J. and Meloche, V. W. 1957.

Elementary Quantitative Analysis: The-

ory and Practice. Row, Peterson and

Comp. Evanston, IL.

Czarneski, M A. and Poisson, P. 2005.

Chlorine dioxide gas decontamination of

a blow/fill/seal machine. Controlled En-

vironments. April, 2005.

http://www.cemag.us/articles.asp?pid=5

15.

Linton, R. H., Han, Y., Selby, T. L., and

Nelson, P. E. 2006. Gas-/vapor phase

sanitation (decontamination) treatments.

21

pp. 401-436. In: G. M. Sapers, J. R.

Gorny, and A. E. Yousef eds. Microbi-

ology of fruits and vegetables. CRC,

Taylor and Francis, Boca Raton, FL.

Mahovic, M. 2004. Use of chlorine,

chlorine compounds and alternatives to

chlorination in the sanitation of tomato

water flume dump tanks. Ph.D. Disser-

tation, University of Florida.

Mahovic, M., Bartz, J. A., Berry, A. D.,

and Sargent, S. A., 2006. Postharvest

treatment of tomato fruit with chlorine

dioxide gas: dose affects fruit quality.

Proc. Fla State Hortic. Soc. (in press).

Weaver-Meyers, P. L., W. A. Stolt, and

B. Kowaleski. 1998. Controlling mold

on library materials with chlorine diox-

ide: an eight-year case study. J. Aca-

demic Librarianship 24:455-458.

White, G. C. 1999. Handbook of chlori-

nation and alternative disinfectants. 4th

ed. Wiley-Interscience Pub., John Wiley

and Sons, Inc. N. Y.

22

Figure 1. Production of ClO2 by sachet supplied by ICA, TriNova.

23

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 1 2 3 4 5 6

Time (h)

Re

co

ve

ry (

% o

f in

itia

l)Total

Source (ClO2)

Sink (ClO2-)

Figure 2. Off-gassing of ClO2 from an aqueous solution and capture of the gas by KI sink.

Aggregate of 3 sachet tests on with tomato fruit inoculated

with E.c.c.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

% d

ecay

7.5ppm/24hr.

7.5ppm/2hr.

0.75ppm/24hr.

0.75ppm/2hr.

+Control

Figure 3. Control of bacterial soft rot at inoculated wounds by treatment with ClO2 gas.

24

1.6 mg ClO2 vs Erwinia (106 cfu/ml) in green

fruits at 72 hrs (6 wounded + 0-5 kg unwounded

fruits)

R2 = 0.9436

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

0 kg 2 kg 3 kg 4 kg 5 kg

Figure 4. Bacterial soft rot control by off-gassed ClO2 where weight of fruit affects level

of control.

25

Aqueous Delivery of ClO 2 vs E.c.c.

R2

= 0.991

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

3.2 1.6 0.8 0.4 0.2

ClO 2 delivery (in mg)

Figure 5. Bacterial soft rot control with increasing doses of ClO2.

26

Fig. 6. An example of control of bacterial soft rot by application of increasing doses of

ClO2.

27

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

3 boxes, 99mg/2hr 3 boxes 88mg/24hrs 1 box, 88mg/24hrs 1 box, 528mg/24hrs 1 box, 99mg/2hrs

Treatment

% d

eca

y 7

2h

rs a

fter t

rea

tmen

t

Fig. 7. Scale up tests with one to three boxes of tomatoes.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Control -

Previous tests

Plexi-Glass Al Foil Cardboard Cardboard

(not as a

barrier)

Drum-liner

(not as a

barrier)

Control

Barrier type

% o

f sta

rtin

g C

lO2 d

ose a

fter

2 h

Fig. 8. A comparison of different materials as sinks for ClO2.

28

ClO2 with different types of sinks inside of the chambers at given intervals of time.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

15 min 30 min 45 min

Time

Pe

rce

nta

ge

ca

ptu

red

Cardboard

Fruit

Wounded Fruit

Fig. 9. Comparison of a tomato box to fruit or wounded tomato fruit as sinks for ClO2.

29

Fig. 10. Damage to the stem scar associated with the use of a 10_ dose of ClO2.

30

Breeding Tomatoes for Florida

J. W. Scott

Gulf Coast Research & Education Center

University of Florida, IFAS

14625 CR 672

Wimauma, FL 33598

W. Klassen

Tropical Research & Education Center

University of Florida, IFAS

18905 S.W. 280th Street

Homestead, FL 33031

Abstract. Fusarium crown and root rot resis-

tant hybrid ‘Crown Jewel’ with resistance

from an IFAS parent has been released by

Seminis and it performed well on grower

farms in Southwest Florida in winter 2006.

Several hybrids including Fla. 8413 and Fla.

8414 with Fusarium crown rot resistance

have been promising in IFAS and grower tri-

als. Most have inbred Fla. 8293 as the resis-

tant parent. High lycopene (crimson),

Fusarium wilt race 3 resistant, Fla. 8153 will

be released in 2006 with the name ‘Flora-

Lee’ as a premium variety to better compete

with greenhouse tomatoes in the supermar-

ket. Heat-tolerant hybrid Fla. 8428 yielded

well in summer 2005 and spring 2006 trials

and will be entering stage 3 testing. Spotted

wilt resistant, heat tolerant hybrids Fla.

8363 and Fla. 8367 will also be entering

stage 3 testing. Two of 8 stage 2 TYLCV

resistant hybrids were selected for further

testing while 7 of 57 new hybrids were se-

lected for stage 2 testing.

Introduction. Improved varieties are needed

to keep the Florida tomato industry com-

petitive in a changing world. Improvements

include the areas of yield, pest resistance,

and fruit quality. Florida’s geography offers

many challenges for tomato improvement,

because high temperatures limit fruit set and

are conducive to disease and insect prob-

lems. There are no neighboring states with

similar latitudes to most of Florida, so there

is less help in solving agricultural problems

than there is in many states. Although pri-

vate companies have tomato breeding pro-

grams that develop varieties for Florida,

these companies are not set up to handle

many of the long-term, high-risk projects

that could prove valuable in the future. The

University of Florida tomato breeding pro-

gram aims at such projects and works in

partnership with private companies to de-

liver improved varieties to benefit the Flor-

ida tomato industry.

Much of the groundwork for the develop-

ment of heat-tolerant varieties was done at

the University of Florida (Scott et al., 1986).

‘Solar Set’ was an important commercial,

heat-tolerant variety for 11 years after it was

released (Scott et al., 1989). The improved

heat-tolerance in ‘Solar Fire’, released in

2003, will hopefully be of benefit to growers

in a future with fewer hurricanes than in

2004. We now have Fusarium wilt race 3

resistant varieties using a resistance gene dis-

covered in a wild species by this program in

the 1980's (Scott and Jones, 1989, 1995).

Breeding lines with Fusarium crown and root

rot resistance were released in 1999 (Scott

and Jones, 2000) and one is a parent in

‘Crown Jewel’, which has now been released

by Seminis. With the impending loss of

methyl bromide, these pathogens could be-

come more widespread. Other diseases such

as bacterial wilt and spotted wilt occur in

31

Florida, but cause far more damage in other

regions of the world. If these diseases be-

come more prevalent here, resistant varieties

will prove beneficial. Tomato yellow leaf

curl virus (TYLCV) is a serious threat to

Florida tomato production (Polston et al.,

1999) and some crops have sustained severe

losses in the last few years. Hazera and

Seminis have recently released TYLCV resis-

tant varieties but they have not been adapted

by Florida growers. Our project has been

ongoing since 1990 utilizing different resis-

tance genes derived from the wild species

Lycopersicon chilense. It appears that four

genes have been introgressed, with two genes

needed in a variety to provide resistance.

These genes must be incorporated into both

parents of a hybrid because the resistance is

not dominant. This makes the breeding of

finished varieties more difficult but such hy-

brids are presently being evaluated and this

is discussed herein. Molecular markers

linked to the resistance genes are being de-

veloped that will accelerate future breeding

progress and these will be provided to all

tomato breeders for their use and benefit to

the Florida industry.

Tomatoes have met with dissatisfaction in

the marketplace. Essentially, this relates to

compromises that are made in providing fruit

that will ship well. Solutions to this problem

are not simple. Research is needed to pro-

vide tomatoes that will be more acceptable

to consumers. On the bright side, Nugyen

and Swartz (1999) and others have shown

that lycopene, the red pigment in a tomato,

has strong antioxidant properties that reduce

several cancers. Work in the breeding pro-

gram has been ongoing for 25 years with a

crimson gene (ogc) that improves internal

tomato color and increases lycopene content.

Seven breeding lines with this gene have been

released to seed companies over the last 11

years. Crimson varieties may be a boon to

the Florida industry in the near future. Ge-

netic alteration of plant architecture might

provide ground tomatoes that reduce labor

costs for staking and harvesting. This could

be important for future production in Flor-

ida. This is another long-term, high risk pro-

ject that is being pursued in our program and

is not likely to be attempted by the private

sector. Florida Tomato Committee funding

has been imperative to the operation of this

breeding program, an investment that has

and will continue to pay dividends. Objec-

tives of this project were:

1) To develop varieties or breeding lines

resistant to soilborne pathogens.

2) To develop improved heat-tolerant

inbreds and hybrids.

3) To develop commercially acceptable

breeding lines and hybrids resistant to gemi-

niviruses or spotted wilt virus.

4) To improve fruit quality and post-

harvest characteristics.

5) To develop commercial hybrids for

the Florida tomato industry.

Objective 1.

Methods. There were 74 lines screened for

Fusarium wilt race 3 and 85 lines screened for

Fusarium crown rot in summer 2005, fall

2005, and spring 2006. There were 67 lines

inoculated with the bacterial wilt pathogen in

fall 2005 but the inoculation failed. The in-

oculation also failed for a bacterial wilt ex-

periment in summer 2005 with eight entries.

In spring 2006, 124 lines were screened for

32

bacterial wilt resistance. A replicated yield

trial comparing advanced inbreds was con-

ducted in spring 2006 that included 1 line

resistant to Fusarium wilt race 3 and 4 lines

resistant to Fusarium crown rot. Summer

2005, fall 2005, and spring 2006 hybrid trials

included 12, 18, and 4 hybrids with resistance

to Fusarium wilt race 3, Fusarium crown rot,

and bacterial wilt, respectively.

Results. The high level of bacterial wilt resis-

tance of large fruited breeding line Fla. 8109

was confirmed in spring 2006. Several lines

with improved horticultural type derived

from Fla. 8109 were selected. Fla. 8293 is a

huge-fruited Fusarium crown rot resistant

line that looked good in some hybrids in fall

2005 and spring 2006. New crown rot resis-

tant inbreds Fla. 8491, Fla. 8499, and Fla.

8497 have all looked good in spring 2006

trials and will be tested in new hybrid com-

binations. Fla. 8296, a putative Fusarium

race 3 resistant inbred, has performed well as

have hybrids from it; Fla. 8461 and Fla.

8462. However, recently we have found Fla.

8296 may not be race 3 resistant and we are

presently checking on this.

Objective 2.

Methods. Heat-tolerant (HT) fruit setting

ability is being incorporated into all phases

of the breeding program. In winter 2006 12

HT lines were evaluated at Tropical Re-

search and Education Center and in summer

2005, fall 2005, and spring 2006, 260 HT

inbreds were evaluated at Gulf Coast Re-

search and Education Center for their per-

formance. There were 14 crosses made with

HT parents in fall 2005 and spring 2006. In

summer and fall 2005 yield trials, 21 HT in-

breds and 24 HT hybrids were tested. At

North Florida Research and Education Cen-

ter in fall 2005, 5 HT hybrids were evaluated

in observation trials. Several HT hybrids

were tested during fall and spring in IFAS

replicated trials at GCREC, IRREC, and

NFREC trials and numerous grower trials.

Results. Hybrid 8428 yielded well in sum-

mer 2005 and spring 2006 trials and will be

tested further for possible release. The HT

level is excellent if fruit size is adequate. Six

other HT hybrids are also in stage 2 testing.

Inbreds Fla. 8044, Fla. 7984B, and Fla. 8282

yielded well in recent testing and hybrids

with these parents are being tested further.

The HT trait is now in several lines listed

under other projects so is more ubiquitous

than indicated here. Heat-tolerant hybrids

with the proper horticultural characteristics

should provide Florida growers with varie-

ties that set fruit more reliably under stress

conditions such as cool or high temperatures.

Objective 3.

Methods.

Geminivirus resistance. There were 307 and

328 lines inoculated separately with ToMoV

and TYLCV, rated for disease severity, and

evaluated for horticultural type in fall 2005

and spring 2006, respectively. There were

57 homozygous-resistant hybrids evaluated

in spring 2006 after crosses were made in the

fall. In spring 2006 24 new hybrids were

made. Eight hybrids were evaluated against

control hybrids in inoculated trials in the fall

and spring.

Spotted wilt resistance. There were 37 lines

with spotted wilt resistance evaluated in fall

33

2005 and spring 2006. Six hybrids were

evaluated in yield trials at GCREC and 7

were evaluated at NFREC. Selection for re-

sistance is done with sequence characterized

amplified region (SCAR) molecular markers

that eliminate the need to screen with thrips

and potentially spread the virus in the West

Coast growing region. There were 21 spotted

wilt resistant hybrids evaluated in spring

2006 using a novel resistance source that

was elucidated in June 2005. These were ad-

vanced to the F2 for further horticultural im-

provement. This resistance source has resis-

tance to a Hawaiian strain of the virus that

overcomes Sw-5 the resistance gene used in

all present commercial hybrids.

Results.

Geminivirus resistance. The goal is to de-

velop commercial quality hybrids with resis-

tance in both parents since resistance in one

parent has not been adequate. Two of 8 hy-

brids tested in fall 2005 and spring 2006 tri-

als were selected for further testing. These

will be compared to; 7 new hybrids selected

for stage 2 testing from 57 evaluated in

spring 2006, 8 hybrids made with UF par-

ents and resistant parents from Hazera

Seeds, and control hybrids. In spring 2006,

205 selections were made and 12 F1s were

advanced to F2. Molecular marker work is

progressing and markers are beginning to ac-

celerate breeding efforts for resistance to

TYLCV although more markers need to be

elucidated. Ultimately we want to combine

TYLCV resistance with heat-tolerance, bac-

terial spot resistance, and other desirable

traits in the same variety.

Spotted wilt resistance. Zeraim Gedera has

seed available for grower testing of hybrid

Fla. 7964. Fla. 8124C is a resistant parent

that is presently being tested in several hy-

brid combinations. The two new hybrids

with the most promise for release are Fla.

8363 and Fla. 8367. These will be tested fur-

ther, especially at NFREC where these and

other hybrids will undergo testing this fall.

Objective 4.

Methods. Fruit quality and shelf-life are

emphasized in all breeding projects. One

method to improve shelf-life is to develop

varieties with ultrafirm (UF) fruit. In the fall

and spring 25 UF inbreds were evaluated.

Another aspect of fruit quality is the devel-

opment of high lycopene varieties by using

the crimson (ogc) gene. This gene is widely

distributed in the various breeding projects.

New hybrids are continually being made and

evaluated.

There were 54 and 58 lines evaluated pri-

marily for improved flavor in the fall and

spring, respectively. Twelve of these lines

were evaluated at TREC. Part of this work

involves the incorporation of high sugars

from a cherry line into large-fruited lines.

The most interesting lines from all flavor

work are tested in flavor trials described in

the grant report on flavor with cooperator

Dr. Elizabeth Baldwin.

Another project is to develop tomatoes that

do not require staking by use of the

brachytic (br) gene that reduces plant height

and increases side shoots. These tomatoes

are called compact growth habit (CGH) to-

matoes. In winter 2006, 103 CGH lines were

evaluated at TREC, and in fall and spring 80

lines were evaluated at GCREC. Jointless

34

tomatoes are also receiving considerable at-

tention with 66 and 51 lines evaluated at

GCREC and TREC, respectively. In spring

2006 100 new jointless hybrids were made

and 31 new jointless CGH crosses were

made.

Results. Fla. 8153 will be released in 2006

under the name ‘Flora-Lee’. Some quality

data from this hybrid is described in the re-

port with Dr. Elizabeth Baldwin. This vari-

ety is a premium tomato for the supermarket

trade and is meant to be harvested at the

breaker stage. The concept is better competi-

tion with greenhouse grown tomatoes. Fla.

8297 is a crimson UF line with very good

flavor that looked good in several hybrid

combinations including the crimson HT F1

Fla. 8485. Fla. 8107 continues to look like

the best CGH hybrid and will be used as a

prototype for stake-less tomato production

(see below). Progress was made in selection

of jointless CGH inbreds which would allow

for mechanical harvest.

Objective 5.

Methods. Hybrids anticipated to have com-

mercial potential are evaluated for horticul-

tural type in replicated breeding plots each

season (stage 1). After the initial evaluation,

those selected for further testing are put in

observation trials at GCREC and NFREC,

with some also being tested at TREC (stage

2). Those that perform well in the observa-

tion trials are tested in state replicated trials

(at the above 3 centers and IRREC) and in

trials on grower farms (stage 3). For seed

production, it is hoped that the initial

crossing produces enough seed for the first

two evaluations. When a hybrid moves onto

the advanced trial phase more seed is pro-

duced at GCREC or sometimes by seed

companies.

Results. Fla. 8107 is a CGH hybrid that gen-

erally yielded reliably in previous testing.

Seed is being made by a commercial seed

company that hopefully will be available by

September 2006. We then want to have it

planted in non-staked, truck rows on Dade

county farms to assess the concept of

growing this type of tomato at various times

of the year. Seed was increased for 52 hy-

brids that are in stage 2 testing. In the fall 15

and 21 crosses were made for stage 1 hybrid

testing for bacterial spot tolerance and to-

mato spotted wilt resistance in addition to

the 57 TYLCV tolerant crosses mentioned

previously. In spring 2006 there were 28,

36, 56, and 8 crosses made to produce bacte-

rial spot tolerant, plum, cherry, and heirloom

hybrids, respectively. These are in addition

to TYLCV, CGH, and jointless crosses al-

ready mentioned.

Literature Cited.

Nguyen, M.L. and S.J. Schwartz. 1999. Ly-

copene: Chemical and biological properties,

Food Technol. 53(2): 38-45.

Polston, J.E., R.J. McGovern, L.G. Brown.

1999. Introduction of Tomato yellow leaf

curl virus in Florida and implications for the

spread of this and other geminiviruses of

tomato. Plant Dis. 8384-988.

Scott, J. W., and J. P. Jones. 1989. Mono-

genic resistance in tomato to Fusarium ox-

ysporum f. sp. lycopersici race 3. Euphytica

40:49-53.

35

Scott, J. W., and John Paul Jones. 1995. Fla.

7547 and Fla. 7481 tomato breeding lines

resistant to Fusarium oxysporum f. sp. ly-

copersici races 1, 2, and 3. HortScience

30(3):645-646.

Scott, J. W., and John Paul Jones. 2000. Fla.

7775 and Fla. 7781: Tomato breeding lines

resistant to Fusarium crown and root rot.

HortScience 35(6):1183-1184.

Scott, J. W., S. M. Olson, J. J. Bryan, T. K.

Howe, P. J. Stoffella, and J. A. Bartz. 1989.

Solar Set: A heat tolerant, fresh market to-

mato hybrid. Fla. Agric. Expt. Sta. Circ. S-

359 10p.

Scott, J. W., R. B. Volin, H. H. Bryan, and

S. M. Olson. 1986. Use of hybrids to de-

velop heat tolerant tomato cultivars. Proc.

Fla. State Hort. Soc. 99:311-314.

36

Breeding Tomatoes for Resistance to all

Races of the Bacterial Spot Pathogen

J. W. Scott

Gulf Coast Research & Education Center

University of Florida

14625 CR 672

Wimauma, FL 33598

J. B. Jones

Plant Pathology Department

University of Florida

Gainesville, FL 23611

Abstract. There are 4 races of the bacterial spot

pathogen that infect tomatoes, but races T3 and

T4 are of primary concern in Florida. Race T3

is widespread, whereas the prevalence of T4 is

not known, although it has been identified

several times in South and West Florida. Parent

lines with T3 resistance have been developed

and crosses made with horticulturally advanced,

susceptible parents to obtain hybrids that have

commercial potential with intermediate resis-

tance. The best of these, Fla. 8314, has had

outstanding yields but fruit size is slightly less

than that of ‘Florida 47’. A decision on release

will be made in fall 2006. Of the hybrids with

tolerance to races T3 and T4, Fla. 8486 and 5

others have been advanced to stage 2 testing.

Three T3 and T4 tolerant inbreds and one T3

tolerant inbred have been advanced to stage 2

testing and are/will be used as parents for im-

proved hybrids. In Ohio 17, breeding lines

(including the 3 in stage 2 testing mentioned

above) had tolerance to races T1 and T2 and

thus appear to have broad spectrum resistance.

Many of these lines are also being selected for

better resistance in Florida. In the long term the

best resistance to race T4 will likely be the

result of combining genes from different

sources. Resistance to T4 was found in PI

128216 and reaffirmed in PI 114490. Plum-

fruited breeding line Fla. 8517 was highly resis-

tant in two experiments and has both PI

128216 and PI 114490 in its pedigree. The

other T4 resistance source appears to be PI

126932 that is in Fla. 8326. Tolerance to race

T4 from Fla. 8326 was confirmed by a single

gene. Twenty-eight F4 selections were made for

improved horticultural traits and resistance

from Fla. 8326 and Fla. 8233, the latter derived

from PI 114490.

Introduction. Bacterial spot is still the most

ubiquitous disease problem of tomatoes in

Florida. Four tomato races have been discov-

ered to date and these belong to four species of

Xanthomonas (Xcv), the bacterial spot patho-

gen (Jones et al., 2005). In Florida, there have

been three races; the original race (T1), the race

discovered in 1991 (T3) (Jones et al., 1995),

and a new race (T4) (Astua-Monge et al.,

2000). Race T3 has largely replaced race T1 in

Florida (Jones et al., 1998). Race T4 has mu-

tated from T3 and appears to be spreading. It

has been found in at least Dade, Manatee, and

Hillsborough counties. It is unknown how

important this race is or might become should

race T3 tolerant varieties be commercially

grown. Race T2 was originally reported from

Brazil, but has now been isolated in some states

in the USA including Ohio.

Our breeding project began in 1983 when we

found Hawaii 7998 was resistant to race T1

(Jones and Scott, 1986). In the early 1990’s

resistance to race T3 was discovered in several

accessions including Hawaii 7981 (Scott et al.,

1995), and this resistance has been incorporated

into advanced T1 resistant breeding lines . Lines

with resistance to T1 and T3 also had tolerance

37

to race T2, whereas lines with resistance to

either race alone were susceptible to T2 (Scott

et al., 2003). This suggests combining bacterial

resistance genes in a line may have unexpected

beneficial effects against other bacterial races.

We found PI 114490 was resistant to race T2 in

the summers of 1995 and 1996 and this was

further verified from 1997 through 2005 at

Wooster, Ohio. PI 114490 also was resistant to

race T1 and tolerant to race T3 (Scott et al.,

2003). In 2003 and 2004 we found PI 114490

was resistant to race T4 (Scott and Jones, un-

published data). The general resistance from PI

114490 needs to be incorporated into advanced

breeding lines. This general resistance could be

important should race T2 migrate into Florida

or might also protect against any new race,

which might emerge in the future. We also

found resistance to races T3 and T4 in Fla.

8326 a breeding line derived from PI 126932.

This resistance may be useful in developing

bacterial spot resistance (T3 and T4) in Florida.

It would be good to find other sources of resis-

tance and develop information on how to better

breed for race T4 resistance and combine this

with T3 resistance. Varieties with T3 and T4

resistance would provide Florida tomato grow-

ers with protection from losses due to bacterial

spot infection and allow for minimal spraying

thus saving money and reducing environmental

concerns. The objectives of this research were:

1) To develop commercial hybrids with

tolerance to bacterial spot race T3 and T4.

2) To develop inbreds with durable resis-

tance for use as parents in commercial hybrids.

3) To determine genetic information about

raceT3 and T4 resistance.

Objective 1.

Methods. There were 32 T3 and T4 tolerant

F1s evaluated in spring 2006. There were 39

hybrids evaluated in non-inoculated replicated

trials during the year. There were 7 and 1 hy-

brids tested in observational and replicated

trials, respectively at NFREC in both fall 2005

and spring 2006.

Results. Fla. 8314 has tolerance to T3 and

marketable yields have been very reliable over

several years of testing. This includes the high-

est yield in the replicated trial at NFREC in fall

2005 and a good performance at GCREC in

spring 2006. However, the fruit size is a little

less than that of Florida 47. Despite the reliable

marketable yields and good fruit firmness, it

was not believed that growers would adapt Fla.

8314 due to a lower percentage of 5 x 6 fruit.

Last year it was decided that Fla. 8314 would

not be released but the outstanding results since

then have rekindled the idea of a release. The

2006 fall performance in IFAS and grower trials

will be the deciding factor. Of the hybrids with

tolerance to both races T3 and T4 that are in

stage 2 testing, Fla. 8486 shows the most

promise at this point although 5 others are still

being tested. Eight new hybrids with tolerance

in both parents and 7 new hybrids with het-

erozygous tolerance were advanced to stage 2

testing.

Objective 2.

Methods. There were 224, 63, 113, and 51

breeding lines (F2 and more inbred) with race

T3 or race T3 and T4 resistance evaluated in

summer 2005, fall 2005, spring 2006, and

winter 2006 (TREC), respectively. Forty

breeding lines and 6 control lines were

38

screened for race T2 resistance in Wooster,

Ohio and T1 resistance in Fremont, Ohio in

summer 2005. At Citra, Florida 70 breeding

lines and 5 control lines were evaluated for T4

resistance in 2005. In a second Citra experi-

ment 6 accessions and 8 breeding lines were

evaluated for T4 resistance.

Results. It appeared that race T4 was the

predominant race at GCREC. Breeding lines

with more advanced horticultural characteris-

tics typically have moderate tolerance levels.

Approximately 12 breeding lines showed tol-

erance of T4 at both Citra and GCREC. Three

lines with T3 and T4 tolerance have been se-

lected for stage 2 testing in a replicated trial at

GCREC in fall 2006. These 3 lines also had

T1 and T2 tolerance in Ohio and thus appear

to have broad spectrum and hopefully durable

resistance. These are lines that may be suit-

able as parental lines to make tolerant hybrids

and some have already been used for this

purpose. Another line with only T3 resis-

tance is also in the stage 2 trial. Seventeen of

the 40 lines tested in Ohio had tolerance to

races T1 and T2 and thus have broad spec-

trum (and durable) resistance. Many of these

are among those selected for resistance in

Florida. These are lines that can be tested for

molecular markers that are being developed as

part of objective 3. If molecular markers can

be used for selection in the future, bacterial

spot tolerance breeding can be done much

more efficiently.

At Citra, accession PI 128216 had T4 resis-

tance; T3 resistance was found in this PI in

the early 1990’s. Several breeding lines with

this accession in their pedigrees also had T4

resistance. Fla. 8517, a breeding line with

short plum fruit, had a high level of T4 resis-

tance at Citra and at GCREC. Some resistance

was seen in PI 126438 and PI 155372-S1 but

surprisingly no resistance was seen in PI

126932. The latter is in the pedigree of Fla.

8326 and some other lines that have shown

T4 resistance in the past. Observations later

in the season revealed that there was little

disease in the tops of the PI 126932 plants

possibly indicating this PI has genes that pre-

vent secondary spread of the T4 bacteria.

Objective 3.

Methods. Research has shown that T4 resis-

tant genes are derived from 3 sources; PI

114490, PI 126932, and PI 128216. Breeding

lines derived from these accessions are being

used in genetic studies. Fla. 8326 has resis-

tance from PI 126932 as well as resistance to

other races from Hawaiian sources. A family

was previously developed with Fla. 8326 and

susceptible parent Fla. 7946. This family was

planted and inoculated with race T4 at Citra

in summer-fall 2005. A F2 between Fla. 8326

and Fla. 8233 was also planted in the same

experiment. All plants were rated for disease

severity. Selections were made from 41 F2

plants that had little disease, with 36 of these

coming from the 8326 x 8233 F2 and 5 from

the 8326 x 7946 F2. The same family and the

41 F3s from the Citra F2s were planted at

GCREC in spring 2006 and inoculated with

race T3. Samples indicated primarily T4 was

in the field however. Fla. 8233, with resis-

tance from PI 114490, and Fla. 8517, with

resistance from both PI 128216 and PI

114490, were both crossed with a susceptible

parent to obtain families similar to that of Fla.

8326. The latter two families were recently

planted and data will be available next year. A

Ph.D. student, supported from other funding

39

is conducting this work as part of his disser-

tation. He will also try to find molecular

markers linked to the resistance genes that

will accelerate the bacterial spot resistance

breeding progress once identified.

Results. From the summer 2005 experiment

the F1 between Fla. 8326 and Fla. 7946 was

intermediate between the parents but skewed

toward susceptibility. This would indicate

that if this resistance alone was used one

would need resistance in both parents to have

useful resistance in the hybrid. The resistance

was conferred by one gene with highly herita-

ble, additive gene action. The data from spring

2006 has not been analyzed yet. However,

the resistance of many F3’s was confirmed

and 28 F4 selections were made for lines with

resistance and good horticultural characteris-

tics. All but one of these were derived from

the family with both 8326 and 8233 in the

pedigree. Thus, many of these likely have re-

sistance genes from both Fla. 8326 and Fla.

8233. A similar strategy will be used to locate

resistant genes from Fla. 8517 (and thus PI

128216). To obtain the highest resistance lev-

els to race T4 will require combining genes

from 2 or more of the resistance sources. We

hope to find molecular markers for the resis-

tance genes and then use these markers to

combine the various genes and conduct future

breeding using marker assisted selection. We

can also find out which genes confer resis-

tance to other races by testing them in Ohio.

Use of broad spectrum resistance genes

should prove durable and not subject to

breakdown by any pathogen races that may

emerge in the future.

Literature Cited.

Astua-Monge, G., G.V. Minsavage, R.E.

Stall, Eduardo C. Vallejos, M.J. Davis, and J.

B. Jones. 2000. Xv4-avrxv4: A new gee -for-

gene interaction identified between Xantho-

monas campestris pv. vesicatoria race T3

and the wild tomato relative Lycopersicon

pennellii. Molecular Plant-Microbe Interac-

tions 13(12):1346-1355.

Jones, J.B., H. Bouzar, G. C. Somodi, R.E.

Stall, K. Pernezny, G. El-Morsy, and J.W.

Scott. 1998. Evidence for the preemptive na-

ture of tomato race 3 of Xanthomonas cam-

pestris pv. vesicatoria. In Florida. Phytopa-

thology. 88:33-38.

Jones, J.B., G.H. Lacey, H. Bouzar, G.V.

Minsavage, R.E. Stall, and N.W. Schaad.

2005. Bacterial spot- Worldwide distribution,

importance and review. Acta Horticulturae

695:27-33.

Jones, J.B. and J.W. Scott. 1986. Hypersensi-

tive response in tomato to Xanthomonas

campestris pv. vesicatoria. Plant Dis. 70:337-

339.

Jones, J.B., R.E. Stall, J.W. Scott, G.C. So-

modi, H. Bouzar, and N.C. Hodge. 1995. A

third tomato race of Xanthomonas campestris

pv. vesicatoria . Plant Dis. 79:395-398.

Scott, J.W., J.B. Jones, G.C. Somodi, and

R.E. Stall. 1995. Screening tomato accessions

for resistance to Xanthomonas campestris pv.

vesicatoria, race T3. Hort. Science 30:579-

581.

40

Scott, J.W., D.M. Francis, S.A. Miller, G.C.

Somodi, and J.B. Jones. 2003. Tomato bacte-

rial spot resistance derived from PI 114490;

inheritance of resistance to race T2 and rela-

tionship across three pathogen races. J. Amer.

Soc. Hort. Sci. 128(5): 698-703.

41

Continued Evaluation of Tomato

Lines That Exhibit a Fruity/Floral

Flavor Character Within a Balanced

Sugar, Acid and Volatile Profile for

Development of a Premium

Commercial Variety

Elizabeth A. Baldwin,

USDA/ARS Citrus & Subtropical

Products Laboratory

Winter Haven, FL

J.W. Scott,

University of Florida Gulf Coast

Research & Education Center

Bradenton, FL

Abstract. Tomato fruit were grown in

replicated plots and the University of

Florida Gulf Coast Research and

Education Center in Bradenton, in

Homestead and in Wimauma (fall, 2005,

and spring of 2006), except for ‘ Scarlet

Red’, which was from a grower trial.

Fruit were analyzed by an experienced

sensory panel for overall flavor,

sweetness and acidity as well as for

chemical components including color,

solids, individual sugars, titratable

acidity, citric acid, vitamin C and aroma

volatiles. A soon-to-be released crimson

(high lycopene) hybrid, Fla. 8153 ‘Flora

Lee’, with a good sugar/acid balance,

was harvested at table ripe and breaker

stages and rated along with tomatoes

typical of the Florida industry. Fla. 8153

(now for the 7th

season) along with other

high flavor genotypes including ‘Scarlet

Red ’, a Harris-Moran variety, and

crimson line, Fla. 050097 received high

ratings from the experienced panel and

were significantly greater than Florida

47 which was significantly greater than a

store-bought tomato on the vine (TOV)

variety for flavor. The Fla. 8153 tomato

was then compared to a Publix

commercial tomato by a non-

experienced consumer panel at Publix

using a 9-point hedonic scale for

appearance and “likeability”, and Fla.

8153 was rated significantly higher

among those panelists who are frequent

consumers of tomato.

The Florida tomato industry would gain

market share with a premium tomato

product that combined the health

benefits of high lycopene and improved

flavor quality. Past experienced sensory

panels have shown a preference for

tomatoes with a good sugar/acid balance

such as Fla. 8153 (soon to be released as

‘Flora Lee’). In this study, we continued

to look at genotypes with high lycopene

backgrounds, good horticultural

characteristics, a good sugar/acid

balance, and sometimes a fruity/floral

flavor note that would differentiate a

potential release from the rest of the

fresh tomato market. High lycopene

tomatoes may garner health benefits due

to the anti-oxidant, anti-cancer activity

of this pigment. Furthermore, the

lycopene pigment is responsible for the

red color of tomatoes, giving a good

appearance, and serves as a precursor for

important flavor compounds. This means

that high lycopene cultivars may result

in healthier, better flavored, and more

attractive tomatoes.

Methods. Tomato (Lycopersicon

esculentum Mill.) genotypes were grown

in a completely randomized block design

with two blocks and 5 plants per plot at

the University of Florida Gulf Coast

Research and Education Center in

Wimauma fall, 2005 and spring, 2006.

‘Scarlet Red ’ was harvested from a

local grower trial. Cultivars, were

sampled in the field from both blocks,

and informally evaluated for flavor by

42

the breeder. Genotypes with superior

flavor were emphasized for comparison

with standard varieties. The “tomato on

the vine” (TOV) was bought at a local

supermarket. All varieties were

harvested at the table ripe stage except

for one sample of Fla. 8153, which was

harvested at the breaker stage and

‘Scarlet Red ’ which was harvested pink.

In fall 2005, tomatoes were analyzed by

an experienced panel (30 panelists) who,

sampled tomato wedges, which

represented at least 4 fruit per cultivar.

Sub-samples were taken 3 times during

the panel session and prepared for

analyses of color and flavor components

by measuring solids, sugars, acids, color,

titratable acidity, vitamin C and aroma

compounds with refractometer, HPLC,

chromometer, spectrophotometer, titrator

and gas chromatograph (GC). In spring

2006 the line Fla. 8153 was submitted

for a non-experienced consumer trial at a

Publix store in Gainesville for

comparison to a commercial Publix

product for appearance and “likeability”.

There were 104 panelists (Publix

shoppers) who were later divided into

two groups who bought tomatoes once a

week or less (42 panelists) and those

who bought more than once a week (62

panelists).

Results. For fall 2005, the experienced

panel rated ‘Scarlet Red ’, Fla. 8153 and

Fla. 050097 (another crimson genotype

assessed by the breeder as having good

flavor and appearance in the field)

highest for flavor, sweetness, and for

Fla. 8153, acidity as well. Florida 47 and

the TOV were rated lowest for flavor,

sweetness, and ‘ Scarlet Red’ was rated

lowest for acidity (Table 1). We felt

strongly that the slight drop off in flavor

for Fla. 8153 harvested at the breaker

stage was due to the fruit not being quite

table ripe when sampled as opposed to

their stage of harvest. For spring 2006,

Fla. 8153 was rated highest for

appearance and likeability by the Publix

consumers, but was significant for

likeability only for the consumer group

who bought tomatoes more than one a

week (Table 2).

Table 1. Experienced panel in Fall 2005. Ratings on a 1-9 scale where higher numbers

indicate more sweetness and acidity and preferred flavor quality.

Genotype, Breeder comments Flavor Sweetness Acidity

Scarlet Red, good flavor 5.31 az

5.31 a 2.94 c

Fla. 8153, table ripe, high lycopene 5.327a 4.46 b 4.03 ab

Fla. 050097, high lycopene,

balanced, aromatic

5.14 a 4.34 b 4.46 a

Fla. 8153, breaker, high lycopene 4.76 ab 4.00 bc 4.18 a

Florida 47 4.17 b 3.49 cd 3.97 ab

TOV – Store-bought 3.26 c 3.15 d 3.56 bzMean separation in columns by Duncan’s multiple range test at P < 0.1.

43

Table 2. Spring 2006, non-experienced panel of Publix shoppers in spring, 2006

conducted by Dr. Charlie Sims, UF, IFAS. Ratings on a 1-9 scale where higher numbers

indicate preference.

A) Less than once-a-week consumers of tomato:

Genotype Appearance Likeability

Fla. 8153 7.09 az

6.43 a

Publix tomato 5.67 b 6.14 a

B) More than once-a-week consumers of tomato

Genotype Appearance Overall flavor

Fla. 8153 7.77 az

7.61 a

Publix tomato 6.03 b 6.64 bzMean separation in columns by Duncan’s multiple range test at P < 0.1.

Chemical data for fall 2005 (sugars,

acids and color) tomatoes sampled by

the experienced panel showed that total

sugars and sucrose equivalents (indicator

of sweetness) were highest in Fla. 8153,

harvested table ripe, and ‘Scarlet Red ’

(Fig. 1) as well as the solids/acid ratio

(SS/TA, Fig. 2). Solids (Brix) was

highest in ‘Scarlet Red ’ (Fig. 1) and

titratable acidity was highest in Fla.

050097 (Fig. 2, true of citric acid level

as well, data not shown). Red color (as

indicated by lower hue values) was

highest in Fla. 8153 followed by Fla.

050097 as expected since these are high

lycopene genotypes and contain the

crimson gene (Fig. 3). Vitamin C

(ascorbic and dehydroascorbic acids)

were highest in Fla. 8153 harvested table

ripe and ‘Scarlet Red ’, harvested pink

(Fig. 4). Later harvest maturity may play

a role in the levels of vitamin C. Volatile

data for aldehydes (generally green,

grassy, earthy) show that Fla. 050097

samples were high in hexanal, cis-3- and

trans-2-hexenal, trans-2-pentenal and

benzylaldehyde (peachy) (data not

shown). Florida 47 was high in cis-3-

hexenal, trans-2-pentenal, trans-2-

heptenal, benzanldehyde and

methylbutanal. Fla. 8153 was high in

trans-2-heptenal and low in cis-3- and

trans-2-hexenal. ‘Scarlet Red ’ was high

in trans-2-pentenal, trans-3-heptenal,

methional (potato) and very high in

methylbutanal. TOV was low in

methybutanal. For ketones (generally

fruity/floral, data not shown), Fla.

050097 was high in acetone, 1-penten-3-

one, octanone (mushroom), and furanone

(cotton candy). Fla. 8153 was high in

geranylacetone and 1-methyl-5-hepten-

2-one (lycopene-derived volatiles).

‘Scarlet Red ’ was high in acetone,

octanone, 6-methyl-5-hepten-2-one, and

geranylacetone.

Conclusions. Fla. 8153, soon to be

released as ‘Flora Lee’, is an attractive

tomato with enhanced nutrition and

flavor. ‘Scarlet Red’ is also a good

flavored tomato as is the UF line

050097. Fla. 8153 and ‘Scarlet Red’

were high in sugar/acid ratio and vitamin

C, while Fla. 8153 and 050097 had more

red color (lower hue). All were fairly

high in sugars and some important

volatiles.

Fig. 1 Sugar data

Fig. 2 Acid data and solids acid ratio

Fig. 3 Color data

Fig. 4 Vitamin C data

Sugars

0

1

2

34

5

6

7

Fla.

050097

FL8153Br Scarlet

RedCultivars

Perc

en

t

Total Sugars

Sucrose Equivalenc

Brix

Acids and solids/acids ratio

0

5

10

15

20

Fla.

050097

FL8153Br Scarlet

RedCultivars

Perc

en

t

S.S./T.A.

Titratable Acidity x 1

pH

Total ascorbic acid (Vitamin C)

0

10

20

30

40

50

60

Fla. 050097 FL8153Br Scarlet RedCultivars

mg

s/1

00 m

ls

215 nm

Color

0

1020

30

4050

60

Fla. 050097 FL47 FL8153Br FL8153R Scarlet Red TOVSTORE

Cultivars

Chroma

Hue

44

45

TYLCV-resistant Tomato Cultivar Trial

and Whitefly Control Strategies

Kent Cushman and Phil Stansly

Southwest Florida Research and

Education Center

Immokalee, FL

Abstract. Tomato yellow leaf curl virus

(TYLCV) and tomato spotted wilt virus

(TSWV) are common diseases of tomato in

southern and northern Florida, respectively.

Two trials were conducted at the Southwest

Florida Research and Education Center in

Immokalee during Spring 2006. One trial

compared 12 entries of TYLCV-resistant

genotypes to the susceptible cultivar Florida

47. Whitefly populations were low until first

harvest and disease incidence was low

throughout the trial. ‘Florida 47’ and two

entries from Abbott & Cobb exhibited dis-

ease incidences of 5% to 8%, indicating

these entries were not resistant genotypes.

TYLCV was not detected among the other

entries. HA 3075 produced the highest total

yield of three harvests, though its total yield

was similar to that of S-50257, VT-60774,

and VT-60780. HA 3075 was the only entry

to produce significantly greater total yield

than ‘Florida 47’. HA 3075 also produced

the highest yield of extra large fruit, though

yield of this size was similar to that of

‘Florida 47’. BHN 745 produced the largest

average fruit size of extra large, at 9.4

oz/fruit, and this was similar to that of

‘Florida 47’ and ‘Tygress’ at 9.1 oz/fruit.

TYLCV-resistant entries that could be rec-

ommended for observation in small plant-

ings are HA 3075, S-50257, VT-60774, VT-

60780, and BHN 745, though some of these

entries had a flattened globe rather than a

deep globe shape. Another trial was con-

ducted that spring at SWFREC to evaluate

the interaction of cultivars Tygress

(TYLCV-resistant) and Florida 47 (TYLCV-

susceptible) and control strategies that in-

cluded selected combinations and rates of

JMS Stylet oil, Platinum, Courier, Admire,

Knack, Oberon, and a growth inhibitor Ni-

chino 0101. The resistant variety showed

little or no virus symptoms, resulting in a

trend toward better yield although the differ-

ence was not significant, probably because

of low virus incidence. However, unsprayed

resistant or susceptible plants yielded the

same. Nichino 0101 provided control of

adult whiteflies comparable to the local

standard. Weekly oil treatment after the

Admire drench also provided good whitefly

control although the yield suffered some-

what. The trial did not demonstrate a clear

advantage to using the resistant variety un-

der conditions of low virus pressure, but

there was certainly no disadvantage in util-

izing this form of insurance against the

worst consequences of whitefly and

TYLCV.

Introduction. Commercial tomato growers

in much of the rest of the country try to limit

losses due to a disease vectored by thrips

called tomato spotted wilt virus (TSWV).

Not so in south and central Florida. Here

growers strive to limit losses due to tomato

yellow leaf curl virus (TYLCV), a disease

vectored by whitefly and a problem we

share in common with other tropical and

semi-tropical regions of the world. This re-

port presents results of two trials conducted

in southwest Florida during Spring 2006 to

evaluate management of TYLCV in com-

mercial tomato plantings using resistant cul-

tivars and whitefly control strategies.

Trial 1: Cultivar Evaluation

One way to control losses due to TYLCV is

for the plant to do most of the work. Tomato

cultivars resistant to TYLCV have been

available for many years, but for one reason

or another they have not been well received

by Florida growers. It is demanded of culti-

46

vars used on commercial farms to produce

plants that are strong, disease resistant, and

highly productive and that yield large, round

fruit with excellent holding and shipping

ability. Good choices are available, but often

these cultivars were developed for other

markets, such as markets that prefer smaller-

sized fruit or a more flattened shape.

Twelve entries of TYLCV-resistant cultivars

and numbered breeders’ selections and one

entry of a standard TYLVC-susceptible cul-

tivar (Table 1) were evaluated in a replicated

trial located at the Southwest Florida Re-

search and Education Center (SWFREC).

Seed were planted in flats and grown on site.

Plants were then transplanted to the field on

Feb. 20. Seed of Zeraim Gedera arrived late

and were also planted in flats but trans-

planted to the field on Feb. 24. The crop was

grown on raised beds with black plastic

mulch and was irrigated and fertilized with

drip tubing. A standard insect and disease

control program was used throughout the

entire duration of the crop, including an imi-

dacloprid drench at transplant and whitefly

control thereafter. The goal of the trial was

to evaluate horticultural characteristics of

each entry and not the level of virus resis-

tance. Tomatoes were harvested three times,

May 10, 24, and June 6. At each harvest,

marketable fruit were separated by mature

green and later maturities and then graded

by size, counted, and weighed. Unmarket-

able fruit were separated by cull categories

and also counted and weighed. The experi-

mental design was a randomized complete

block and data were statistically analyzed to

determine significant differences.

Growing conditions were excellent with lit-

tle rainfall and relatively warm, sunny days.

Whitefly populations were low until the first

harvest at which time populations became

well established in the planting. At the time

of final harvest, TYLVC-resistant cultivars

had no virus-affected plants and susceptible

cultivars had a low level of incidence (Table

1). The two entries from Abbott & Cobb had

higher levels of TYLVC disease than the

standard cultivar Florida 47. A previous trial

at this location experienced a high level of

disease in susceptible cultivars (Gilreath et

al. 2000).

HA 3075 (Hazera) produced the highest to-

tal yield, though its total yield was similar to

that of ACR-2012 (Abbott and Cobb), S-

50257, VT-60774, and VT-60780 (Zeraim

Gedera). HA 3075 was the only entry to

produce significantly greater total yield than

‘Florida 47’ (Table 2). HA 3075 also pro-

duced the highest yield of 5x6s, though yield

of this size category was similar to that of

Florida 47 (Table 3). Despite having the

highest yield, HA 3075 did not produce the

largest fruit in this size category. BHN 745

averaged 5x6 fruit of 9.4 ounces and this

was similar to that of ‘Florida 47’ and ‘Ty-

gress’ at 9.1 ounces each. HA 3075 aver-

aged 8.3 ounces per fruit in the 5x6 size

category. S-50260 produced the highest per-

centage of cull fruit, though its percentage of

cull fruit was similar to that of HA 3074, Fla

8477, and BHN 745. Defects of fruit of S-

50260 and Fla 8477 were mostly due to zip-

per scarring and catfacing. Fruit of S-50252

also exhibited a high percentage of zipper

scarring and catfacing compared to most

other entries.

In conclusion, several entries produced total

yields equal to or better than the standard

cultivar. Based on marketable yield, cull

categories, and size and shape of marketable

fruit, TYLCV-resistant entries from this trial

that could be grown for observation in small

blocks on commercial farms are HA 3075,

S-50257, VT-60774, and VT-60780, and

BHN 745.

47

Trial 2: Cultivars in Combination with

Control Strategies

A trial was conducted at SWFREC to evalu-

ate the interaction of cultivar and control

strategies. One TYLCV-resistant cultivar,

Tygress, and one TYLCV-susceptible culti-

var, Florida 47, were planted 22 Feb. 2006

in raised beds with black plastic mulch and

drip irritation. Whitefly control strategies

were applied to cultivars in an unbalanced

experimental design, with more treatments

applied to ‘Florida 47’ than ‘Tygress’. All

treatments (Table 4) were replicated four

times.

Average numbers of whitefly adults during

the first six weeks of the trial were low, al-

though numbers increased dramatically

during the subsequent five weeks. Most

adult whiteflies were observed on untreated

‘Tygress’ plants, although not significantly

more than on untreated ‘Florida 47’. Num-

bers of adults on plants treated with the low

(8 oz) rate of Platinum followed by the stan-

dard spray combination were not different

from either untreated check (Fig. 1). Fewest

whiteflies were observed on plants treated

with Admire at planting, followed by the

low rate of NNI 0101, though not less than

plants receiving the same treatments except

with the higher rate of NNI 0101. These in

turn were not significantly different from

plants sprayed with the standard combina-

tion or with oil following the Admire

drench. Fewest whitefly eggs were seen on

plants sprayed following the Admire drench

with the high rate of NNI 0101 twice and

Courier once or weekly with JMS Stylet oil

(Fig. 2). There were no differences com-

pared to the untreated controls exhibited by

the other treatments.

More small nymphs were seen over all sam-

ple dates on untreated ‘FL-47’ then all

treated plants, with no differences between

untreated varieties. Fewest small nymphs

were seen on plants drenched with Admire

and receiving the standard sprays or the high

rate of NNI 0101, although not significantly

so compared to all other treatments except

JMS oil (Fig. 2). More large nymphs were

seen on unsprayed ‘Florida 47’ than un-

sprayed ‘Tygress’, with no differences be-

tween this latter control and all remaining

treatments except the high (11 oz) rate of

Platinum (Fig. 2).

No virus symptoms were seen on the ‘Ty-

gress’ plants except for one possible case in

an unsprayed plot. However, few plants

were observed with symptoms of TYLCV

until the end of the trial, and the distribution

of symptomatic plants did not seem to cor-

relate well with whitefly populations on the

susceptible variety. For instance, plants

treated with 11 oz of Platinum exhibited

significantly higher incidence of diseased

plants than the untreated susceptible control.

All treated plants yielded more marketable

fruit than untreated plants, with most har-

vested from ‘Tygress’ receiving the standard

treatment, although not significantly more

than all other treatments except plants oil,

Platinum and the control. Similarly, fewest

culls were taken from plants receiving the

standard treatment regardless of variety,

though not significantly less than plants re-

ceiving either rate of Platinum, NNI 0101 or

oil.

In conclusion, resistant varieties showed lit-

tle or no virus symptoms, although yields

were not significantly different from sus-

ceptible plants, probably because of low vi-

rus incidence. Nichino 0101, a feeding in-

hibitor, provided control of whiteflies com-

parable to the standard treatment of adults.

Weekly oil treatment after the Admire

drench also provided good whitefly control

although the yield suffered somewhat, com-

parable to plants treated with Platinum at the

48

low rate followed by the standard spray

regimen. Although this trial did not demon-

strate a clear advantage to using the resistant

variety under conditions of low virus pres-

sure, neither was there any disadvantage.

Thus, use of ‘Tygress’ in the spring growing

season could provide an extra measure of

security to the grower, over and above the

standard insecticidal regime.

Literature Cited

Gilreath, P., P. Stansly, K. Shuler, J. Pol-

ston, T. Sherwood, G. McAvoy, and E.

Waldo. 2000. Tomato yellow leaf curl virus

resistant tomato variety trials. Proc. Fla.

State Hort. Soc. 113:190-193.

49

Table 1. Cultivars and advanced breeder’s varieties evaluated in this study along with seed

source, fruit shape, and percentage of diseased plants observed in the variety trial.

Variety SourceDiseased plants

(%)z

Florida 47 Seminis 5

Tygress Seminis 0

Fla 8477 UF/IFAS 0

BHN 745 BHN 0

HA 3074 Hazera 0

HA 3075 Hazera 0

ACR-242 Abbott & Cobb 8

ACR-2012 Abbott & Cobb 7

S-50252 Zeraim Gedera 0

S-50257 Zeraim Gedera 0

S-50260 Zeraim Gedera 0

VT-60774 Zeraim Gedera 0

VT-60780 Zeraim Gedera 0

z Percentage of TYLVC-affected plants at end of trial, after third harvest. Values are means of

four replications of 10-12 plants.

Table 2. Marketable yield by size category, percent of total yield at breaker stage or beyond, and average weight of 5x6 (extra-large),

6x6 (large), and 6x7 (medium) sized fruit.

Marketable yield (boxes/acre) z

% Avg fruit wt (oz)

Treatments 5x6 6x6 6x7 Total Color 5x6 6x6 6x7

Florida 47 2,380 ab 158 h-j 226 e-g 2,760 b-e 30 ef 9.1 a 5.6 a-c 4.7 ab

Tygress 2,310 b 115 j 131 g 2,550 d-f 29 ef 9.1 a 5.5 a-d 4.6 a-d

Fla 8477 1,760 de 369 d-f 379 cd 2,500 ef 37 de 7.6 de 5.6 ab 4.7 a

BHN 745 2,240 bc 133 ij 184 fg 2,560 d-f 20 f 9.4 a 5.5 b-d 4.4 d

HA 3074 2,120 b-d 265 f-h 267 d-g 2,650 c-e 53 bc 8.2 bc 5.6 a-c 4.8 a

HA 3075 2,780 a 238 g-i 248 d-g 3,270 a 37 de 8.3 b 5.7 a 4.6 a-c

ACR-242 2,040 b-d 396 de 331 de 2,760 b-e 54 a-c 7.5 de 5.5 a-d 4.5 b-d

ACR-2012 2,200 bc 396 de 368 cd 2,960 a-c 44 cd 7.9 cd 5.7 a 4.8 a

S-50252 1,880 cd 519 bc 489 bc 2,880 b-d 63 a 7.4 ef 5.6 a-d 4.7 ab

S-50257 1,420 ef 757 a 761 a 2,940 a-c 64 a 6.9 g 5.5 dc 4.4 cd

S-50260 1,290 f 465 cd 481 bc 2,240 f 61 ab 7.1 fg 5.4 d 4.6 a-d

VT-60774 2,360 b 332 e-g 317 d-f 3,010 a-c 39 de 7.9 cd 5.5 b-d 4.6 a-d

VT-60780 1,880 cd 585 b 591 b 3,050 ab 61 ab 7.6 de 5.5 a-d 4.6 a-d

Significance <.001 <.001 <.001 0.001 <.001 <.001 0.063 0.017

z Marketable yield is mature green fruit plus later maturities but minus unmarketable (cull) fruit. Values are means of four replications

of 10 or 12 plants. Means followed by the same letter are not statistically different at P 0.05.

51

Table 3. Unmarketable (cull) categories and total unmarketable weight. Blossom end scar (BES), zipper and catface, sunscald and

yellow shoulder (SS, YS), radial and concentric cracking (Crk), misshapen (Mspn), and other cull categories.

Unmarketable fruit by cull category (%) z

Total Cull wt

Treatments BES Zip +Catface SS, YS Crk Mspn Other Total (boxes/acre)

Florida 47 0.3 de 4.5 f-h 0.5 1.2 c-e 1.8 ab 1.3 de 9.6 e-g 326 bc

Tygress 0.3 de 7.1 de 0.5 1.1 c-e 0.8 cd 2.5 bc 12.2 de 372 bc

Fla 8477 1.3 c 10.4 b 0.7 0.4 e 1.2 bc 3.8 a 17.8 ab 710 a

BHN 745 2.8 b 7.9 cd 0.5 2.1 bc 1.0 b-d 2.6 a-c 16.9 a-c 690 a

HA 3074 2.5 b 6.4 d-f 0.7 4.7 a 0.8 cd 3.0 ab 18.2 ab 726 a

HA 3075 1.1 cd 1.4 i 1.0 2.2 bc 1.4 bc 1.9 b-e 9.0 f-h 362 bc

ACR-242 0.6 c-e 2.7 hi 0.4 0.7 de 1.3 bc 2.1 b-d 7.7 gh 241 c

ACR-2012 3.7 a 5.3 e-g 0.5 1.8 b-d 2.3 a 2.0 b-e 15.6 bc 711 a

S-50252 0.7 c-e 9.9 bc 1.4 0.6 de 0.3 d 1.7 c-e 14.6 cd 592 a

S-50257 0.1 e 5.1 e-g 1.2 0.5 e 1.2 bc 0.9 e 8.9 f-h 322 bc

S-50260 0.3 de 13.7 a 1.7 0.4 e 0.7 cd 2.5 bc 19.3 a 700 a

VT-60774 0.4 de 3.2 g-i 1.4 2.9 b 0.7 cd 2.4 b-d 11.0 ef 419 b

VT-60780 0.7 c-e 1.5 i 1.3 0.4 e 0.9 b-d 1.7 c-e 6.5 h 229 c

Significance <.001 <.001 0.314 <.001 0.006 <.001 <.001 <.001

z Unmarketable (cull) categories reported as percentage of total number of marketable plus unmarketable fruit. Values are means of

four replications of 10 or 12 plants. Means followed by the same letter are not statistically different at P 0.05.

Table 4.

Week

Treatment Cultivar Product Rate 1 2 3 4 5 6 7 8 9 10 11 12 13 14

R_Chk Tygress untreated --

S_Chk Florida 47 untreated --

R_Stdrd Tygress Admire Pro 4.6L 7 fl oz per acre x

Oberon 2SC 8 fl oz per acre x x

Knack .86L 9 fl oz per acre x x

S_Stdrd Florida 47 Admire Pro 4.6L 7 fl oz per acre x

Oberon 2SC 8 fl oz per acre x x

Knack .86L 9 fl oz per acre x x

Plat_L Florida 47 Platinum 2SC 8 fl oz per acre x

Oberon 2SC 8 fl oz per acre x x

Knack .86L 9 fl oz per acre x x

Plat_H Florida 47 Platinum 2SC 11 fl oz per acre x

Oberon 2SC 8 fl oz per acre x x

Knack .86L 9 fl oz per acre x x

Oil Florida 47 Admire Pro 4.6L 7 fl oz per acre x

JMS Stylet Oil 1 % v/v x x x x x x x x x x

Nich_L Florida 47 Admire Pro 4.6L 7 fl oz per acre x

Courier 40SC 12 fl oz per acre x

NNI-0101 0.2 lb per acre a.i. x x x

Nich_H Florida 47 Admire Pro 4.6L 7 fl oz per acre x

Courier 40SC 12 fl oz per acre x

NNI-0101 0.3 lb per acre a.i. x x x

Figure 1. Average number adult whiteflies collected in 4 beats over 11 sample weekly dates.

Columns designated by the same letter represent means that are not significantly different (LSD, P < 0.05)

a

ab

abcbc

cdcde cde

de e

0

5

10

15

20

25R_CHK

S_CHK

Plat_

L

PLAT_H

S_STDR

OIL

R_STDR

NichH

NichL

Ad

ult

s p

er

4 b

eats

54

Figure 2. Average number of eggs, small nymphs and large nymphs over 10 weekly sample dates.

0

1

2

3

4

5

6

7

S_C

HK

R_C

HK

OIL

PLA

T_H

Nic

hL

Pla

t_L

R_S

TDR

Nic

hH

S_S

TDR

Nu

mb

er/

7c

m2

Eggs

Small Nymphs

Large Nymphs

55

Figure 3. Mean incidence of plants with TYLCV symptoms in tomato plots.

Columns designated by the same letter represent means that are not significantly different (LSD, P < 0.05)

0

5

10

15

20

25

30

35

40PLA

T_HS_S

TDR

Nic

hH

S_C

HK

Pla

t_L

Nic

hL

OIL

R_C

HK

R_S

TDR

TY

LC

V (

%)

a

ababc

bc bcbc bc

bcc

56

Figure 4. Mean weight from 8 plants of marketable and unmarketable fruit yield from 6 harvests.

Columns designated by the same letter represent means that are not significantly different (LSD, P < 0.05). Columns repre-

senting marketable yield were analyzed separate from columns representing unmarketable yield.

0

10

20

30

40

50

60

70R

_STD

R

Nic

hL

S_S

TD

RPLA

T_H

Nic

hH

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Pla

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R_C

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LB

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pla

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Marketable

Culls

a

a a a a

b b

c c

a

b

ab

bc c

dd

57

Agar Media and Laboratory

Methods for Detection and

Evaluation of Copper Resistance

Among Bacterial Pathogens of

Vegetables in Florida and Dis-

ease Control in the Greenhouse

Ken Pernezny, Russell Nagata Nikol

Havranek, and Jairo Sanchez,

IFAS, Everglades Research and Educa-

tion Center, University of Florida,

3200 E. Palm Beach Rd.

Belle Glade, FL 33430

Introduction and Background. Bacte-

rial diseases are some of the most seri-

ous pest problems confronting vegetable

growers in Florida. Control of bacterial

diseases is difficult, partly due to the

humid, warm weather and frequent rain-

fall characteristic of Florida’s climate.

Growers routinely spray copper com-

pounds on vegetable crops in an attempt

to mitigate losses from one or more fo-

liar bacterial diseases. However, control

is all-too-often less than desirable. This

lack of efficacy appears to be related to

the frequent occurrence of copper-

resistant strains of vegetable bacterial

pathogens (Adaskaveg & Hine, 1985;

Marco & Stall; Pohronezny et al., 1994;

Ritchie & Dittapongpitch, 1991; Jones et

al., 1991).

Several agar media and laboratory pro-

tocols have been used to screen strains

of bacteria for resistance to copper. Stall

et al. (1986) used plates of nutrient agar

amended with 200 g/ml of CuSO4 · 5

H2O to screen for resistance to copper

among pepper strains of Xanthomonas

axonopodis pv. vesicatoria. Applying

this technique, 114 of 118 strains of X.

axonopodis pv. vesicatoria collected

from commercial pepper fields in Flor-

ida between 1989 and 1991 were found

to be resistant to copper (Pohronezny et

al., 1992). This same procedure was

used to screen for copper resistance of

tomato strains of X. campestris pv. vesi-

catoria (Jones et al; 1991) and strains of

X. campestris pv. vitians causing bacte-

rial leaf spot of lettuce (Pernezny, et al.

1995).

Studies of copper resistance of strains of

Pseudomonas syringae from citrus and

almond orchards in California utilized

plates of casitone-yeast extract (CYE)

agar amended with several different

CuSO4 concentrations (Andersen et al.,

1991). This approach allowed the re-

searchers to identify a range of responses

to copper challenge dependent on the

dose of copper used. In like manner, us-

ing this technique, strains of P. cichorii

from celery seedbeds were classified as

sensitive, moderately resistant, or highly

resistant to copper (Pohronezny et al.,

1994).

In preliminary experiments, glucose-

nutrient agar (GNA) and CYE agar, both

amended with CuSO4 (aq) , usually led

one to conclude that pepper strains of X.

axonopodis pv. vesicatoria are resistant

or sensitive to Cu, respectively. Which

medium, then, is more likely to represent

the status of copper resistance among

Florida’s strains of pathogenic bacteria

recovered from diseased vegetable

crops?

Several relatively new compounds may

have activity against bacterial diseases.

Tanos® is a relatively new fungicide

marketed by DuPont Corporation. It has

activity against many fungal pathogens

that attack Florida vegetable crops.

However, there have been some reports

58

of efficacy against bacterial diseases.

Little is known about the nature of this

bacterial disease suppression with Ta-

nos®. There is also a little information

about the activity of Actinovate®, Ka-

sumin®, Physpe

®, and ProPhyt

®.

The objectives of this study were to: (i)

compare the growth of strains of X.

campestris pathogens from lettuce (cop-

per rarely used in the field) and pepper

and tomato (historically heavy copper

use) on GNA and CYE agars amended

with CuSO4, (ii) quantify toxicity of

commercial copper compounds and

other agrichemicals to populations of

representative bacterial strains, (iii)

evaluate control of diseases caused by

representative strains in the greenhouse,

and (iv) determine if Tanos, Actinovate,

TM-417, Physpe, and ProPhyt provide

disease control in the greenhouse.

MATERIALS AND METHODS.

Bacterial strains and initial screening

for copper resistance. All bacterial

strains were kept in long-term storage in

sterile 15% glycerol solution at -70 °C.

Nutrient agar amended with 0.5 % (w/v)

glucose (GNA) and a slightly modified

casitone-yeast extract agar (CYE) (1.7 g

casitone, 0.35 g yeast extract, 5 g glu-

cose, and 17 g Noble agar per L distilled

water) were compared for growth of

strains with and without copper amend-

ment. Glucose was substituted for glyc-

erol in the original CYE recipe, because

xanthomonads generally do not grow

well with glycerol as the principal source

of carbon.

Copper sulfate at appropriate concentra-

tions was incorporated (from a filter-

sterilized 0.64 M solution of CuSO4)

into autoclaved media cooled to 55 °C.

A total of 19 strains of X. campestris pv.

vitians from lettuce (Lactuca sativa L.)

36 strains of X. axonopodis pv. vesicato-

ria from pepper (Capsicum annuum L.),

and 39 strains of X. axonopodis pv. vesi-

catoria from tomato (Lycopersicon es-

culentum Mill.) were tested for sensitiv-

ity to copper. Specific treatments were

GNA, GNA + 200 g/ml CuSO4 · 5

H2O, CYE, CYE + 161 g/ml CuSO4 · 5

H2O (equivalent to the originally pub-

lished concentration of 0.64 mM CuSO4)

(Andersen et al., 1991), and CYE + 200

g/ml CuSO4 · 5 H2O. Three replicate

plates of each medium were streaked in

an S-pattern (10 sweeps/plate) with a

loopful of growth of each strain taken

from 3-day-old growth on GNA plates.

Plates were incubated at 28 °C for 72 h.

A visual estimate was made of the

growth on copper-containing media and

expressed as a percentage of the growth

on appropriate control plates without

copper addition. All strains were

screened similarly a second time.

Population dynamics of strains ex-

posed to commercial agrichemicals.

Representative strains of X. campestris

pv. vitians and X. axonopodis pv. vesi-

catoria from both pepper and tomato

were selected for more in-depth popula-

tion dynamics studies. Specific strains

tested were X. campestris pv. vitians, L7

and L11 (both sensitive using GNA and

CYE Cu assays); X. axonopodis pv.

vesicatoria pepper strain P663 (sensitive

in both GNA & CYE Cu assays); pepper

strain P635 and P648 (resistant in GNA

Cu assay but sensitive in CYE CU as-

say); and tomato strains T135 and T193,

59

both resistant in the GNA assay and sen-

sitive in the CYE assay.

Five treatments were tested for their ef-

fects on populations of bacterial strains.

Dosages used in the laboratory were

based on typical rates applied on com-

mercial crops. Suspensions of the fol-

lowing chemicals were freshly prepared

in the laboratory in sterile distilled water

at dosages equivalent to those recom-

mended for field application: 2.4 g/L

copper hydroxide (Kocide 2000®); 2.4

g/L mancozeb (Manzate 75 DF®); a

combination suspension of copper hy-

droxide and mancozeb at the rates listed

above; a combination product of fa-

moxadone and cymoxanil at a rate of 0.6

g/L (Tanos 50 DF®), and a sterile water

control. Ten ml of chemical suspension

or water and 10 ml of ca. 2x108 CFU/ml

suspension of each bacterial strain were

mixed in sterile 50 ml beakers. Beakers

were maintained at room temperature for

2 h and manually agitated every 15 min.

Suspensions were then gravity-filtered

through sterile Watman No. 2 filter pa-

per, serially diluted in a decimal series,

and 100 L of each dilution were plated

in triplicate on GNA and spread with a

sterile, bent glass rod. Plates were incu-

bated at 28 °C for 72 h, and colonies

enumerated on plates with less than 400

colonies per plate. Data were expressed

as log10 CFU/ml. Populations were re-

corded as zero when no colonies were

detected on spread plates from samples

drawn directly from the undiluted fil-

trates. These were three replicate dilu-

tions of each strain/treatment combina-

tion.

Control of bacterial spot in the green-

house using copper bactericides. Ex-

periments were conducted in the green-

house to assess the control of several

bacterial strains with copper bactericide

with and without the addition of man-

cozeb. Pepper seed, cv. Jupiter, were

planted in 10-cm plastic pots in a com-

mercial potting mix (Farfard Soil Mix

No. 2). After emergence, plants were

fertilized once per week with a 20-20-20

soluble fertilizer (1g/L) (Agriliance,

Inc). Tomato, cv. BHN 586, was grown

similarly except that 15-cm plastic pots

were used. Experiments were conducted

in an air-conditioned greenhouse with

maximum temperatures of 26 to 28 °C.

Xanthomonas axonopodis pv. vesicato-

ria, strain P635 (pepper) and strain T193

(tomato), resistant to copper, were

grown for 3 days at 28 °C on nutrient

agar amended with 0.5 % (aqueous

wt/vol) glucose (GNA). Plates were

flooded with sterile phosphate-buffer

saline (PBS; Leben et al., 1968), and re-

sultant suspensions were adjusted

tubidimetrically to approximately 1x108

CFU/ml. Suspensions were then diluted

to 106 -10

7 CFU/ml for inoculum prepa-

ration. Application of bacterial suspen-

sions were made by misting both adaxial

and abaxial leaf surfaces to run-off using

a handheld plastic spray bottle (Wal-

Mart). Two drops of Tween 80 were

added to 660 ml of inoculum suspension

to enhance wetting of leaf surfaces.

Plants were sprayed with chemical

treatments at a 10-day interval before

inoculation and then several times at a 7-

day interval after inoculation. Chemicals

were applied as mists using hand-held

plastic spray bottles. Treatments tested

were copper hydroxide (Kocide 2000)

(0.24 g product/100 ml H2O; 2 lb/100

gal H2O), mancozeb (Manzate 75 DF)

(0.24 g product/ 100 ml H2O; 2 lb/100

gal H2O), and a combination of copper

hydroxide and mancozeb at the same

60

rates, and a water control. The experi-

ment was arranged in a nested design

with three individual plants nested

within each treatment and treatments

assigned randomly within each of three

blocks. Disease ratings were made twice,

9-20 days after inoculation. Theses rat-

ings consisted of an estimate of percent-

age of leaf surface covered by lesions

combined with that lost from the plant

due to premature defoliation.

Other compounds tested for bacterial

spot control. Another series of experi-

ments was carried out to investigate the

efficacy of several new, novel com-

pounds as alternatives to traditional cop-

per/mancozeb applications for manage-

ment of bacterial disease. These com-

pounds were Physpe® (0.45 ml/ 100 ml

H2O), a seaweed derivative thought to

work as a systemic-acquired-resistance

activator; Actinovate® (0.89 g / 100 ml

H2O; 12 fl. oz/100 gal H2O), a biocon-

trol actinomycete; Kasumin® (0.51 ml/

100 ml

H2O; 2 qt/100 gal H2O), an antibiotic

with kasugamycin as the active

ingredient; Tanos® (0.06 g / 100 ml H2-

O; 8 oz/100 gal H2O) + Kocide 2000®

(0.24 g / 100 ml H2O; 2 lb/ 100 gal) +

ProPhyt ® (0.56 ml/ 100 ml H2O; 2 qt /

100 gal H2O) alternated with Kocide

2000® (0.24 g/ 100 ml H2O; 2 lb / 100

gal H2O) + Manzate 75 DF® (0.24 g/

100 ml H2O; 2 lb / 100 gal H2O) +

ProPhyt® (0.56 ml/ 100 ml H2O; 2 qt /

100 gal H2O), SAR elicitors + copper-

based bactericide. The other two treat-

ments were Kocide 2000® (0.24 g/ 100

ml H2O; 2 lb / 100 gal H2O) + Manzate

75 DF® (0.24 g/ 100 ml H2O; 2 lb / 100

gal H2O), and a water control.

Pre-and post-inoculation treatments and

disease rating were as described above

for the copper bactericide experiments.

Data analysis. Data were analyzed using

the Statistical Analysis System (SAS

Institute, Cary, NC). Data were sub-

jected to analysis of variance followed

by mean separation by Waller-Duncan’s

k-ratio t-test. Since the log10 of zero in

undefined, the digit one was added to all

bacterial population estimates before

counts were converted to log10 equiva-

lents. Original zero values are shown in

Tables.

RESULTS. Conclusions about the re-

sistance of bacterial strains to copper

differed depending on the agar medium

used for qualitative visual assay. Of 94

strains tested, 73 grew as well on GNA

plates amended with CuSO4 as on GNA

plates with no copper (Table 1). These

strains were labeled as resistant to cop-

per. In contrast, none of the 94 strains

grew on CYE plates with copper

amendment, so that 100 % of strains

were classified as sensitive to copper.

All strains of X. campestris pv. vitians

from lettuce were sensitive to copper on

either medium. However, only two of 75

strains of X. axonopodis pv. vesicatoria

were copper sensitive on both media. All

others were recorded as copper resistant

on GNA and copper sensitive on CYE.

Assays of populations of bacterial strains

after exposure to commercial copper hy-

droxide suspensions tended to support

the widespread incidence of copper re-

sistance as indicated by the GNA + Cu

test. In only one of 10 experiments with

strains of X. axonopodis pv. vesicatoria

were populations reduced below 1x108

CFU/ml after 2 hr exposure to copper

hydroxide (Table 2). For strain P635,

61

copper hydroxide did not decrease

populations below the water control. On

the other hand, when strains were rated

as sensitive on both GNA and CYE,

populations were dramatically reduced

by copper hydroxide. Reductions were

on the order of 5 log units or more (Ta-

ble 2).

Addition of mancozeb to copper hy-

droxide usually resulted in substantial

increases in mortality of strains that were

resistant to copper hydroxide alone (Ta-

ble 2). For three of these strains (T135,

T193, and P648), no bacterial cells were

detected after copper/mancozeb treat-

ment. For one strain, P635, even the ad-

dition of mancozeb did not reduce

populations to a desired level: popula-

tions were still above 106 CFU/ml after 2

hr of in vitro exposure.

Mancozeb and Tanos® did not have a

consistent direct toxic effect on any of

the bacterial strains (Table 2). Recorded

reductions, if any, were always less than

one log unit, and no populations were

less than 1x108 CFU/ml.

A combination spray of copper and

mancozeb was effective in reducing

bacterial spot of pepper in two experi-

ments using a copper-resistant strain

(Table 3). In one of the experiments,

when disease levels were about 20 % in

the control, mancozeb by itself was

nearly as efficacious as the combination

treatment. In a second experiment, when

disease severity was higher (39 – 50 %

in the control), only the combination of

copper hydroxide and mancozeb signifi-

cantly reduced disease severity. Similar

results were seen with tomato strains of

X. axonopodis pv. vesicatoria (Table 5

& 6).

Kasugamycin was the most promising of

a group of newer, novel compounds

tested for bacterial spot control of pep-

per. Disease severity was reduced by

about _ in both pepper experiments us-

ing this antibiotic (Table 4). Two other

novel compounds, a seaweed derivative,

Physpe®, and a biological bactericide,

Actinovate®, based on propagules of the

actinomycete, Streptomyces lydicus,

were not very effective. The combina-

tion of Tanos® + copper hydroxide +

mancozeb did not perform any better

than the standard copper + mancozeb

treatment.

DISCUSSION. The protocol and, espe-

cially, the culture medium chosen to

screen bacterial strains can profoundly

affect conclusions concerning classifica-

tion of strains as copper resistant. Most

of the Xanthomonas strains in this study

were judged resistant when using GNA

amended with copper (Stall et al., 1986)

and sensitive when using CYE (Ander-

sen et al., 1986) plus copper. GNA ap-

pears to be a more suitable medium for

screening of Xanthomonas strains from

Florida. This is most evident when ex-

amining strains that show different re-

sponses to copper incorporated into the

two media. Strains with differential re-

sponses were always judged resistant on

GNA + Cu and sensitive on CYE + Cu.

The in vitro population assays confirm

that the GNA screen was more likely to

reflect the activity of copper hydroxide

bactericide on in vitro populations of X.

axonopodis pv. vesicatoria from pepper

or tomato. For example, 2 hr exposure of

resistant strain P635 to copper hydroxide

in vitro did not reduce populations below

that in the control. In only one experi-

ment of eight using strains labeled re-

sistant on GNA + Cu was the population

reduced below 1x108 CFU/ml, making it

62

certain that these strains are resistant to

copper. Therefore, the initial classifica-

tion of strains with respect to copper re-

sistance was better determined with

GNA as the basal medium into which

copper sulfate was added.

The usefulness of media for screening

for copper resistance depends on the

host/pathogen system under investiga-

tion. For example, CYE medium

amended with copper was extremely

useful for screening Pseudomonas

cichorii strains recovered from celery

seedbeds (Pohronezny et al., 1994). Us-

ing CYE, it was possible to broadly clas-

sify strains as highly resistant, moder-

ately resistant, or sensitive to copper.

These classifications corresponded

nicely to in vitro population dynamics

studies similar to those reported here.

CYE + Cu was also very useful for

studies of copper resistance among P.

syringae strains from fruit trees (Ander-

sen et al., 1991) and ornamentals

(Scheck & Pscheidt, 1998). It may be

that GNA + Cu is more appropriate for

screening xanthomonads for copper re-

sistance and CYE for pseudomonads.

However, more strains of additional

pathovars of both genera need to be

tested before any generalizations can be

made.

Addition of mancozeb to copper hy-

droxide usually resulted in substantial

increases in mortality of the pathogen.

For three of the strains tested, no bacte-

rial cells were detected in samples taken

from copper hydroxide + mancozeb

treatments. This may be due to increases

in concentration of Cu2+

ions in solution

when the mixture is prepared (Marco

and Stall, 1983; Menkissoglu and Lin-

dow, 1991), and the bactericidal proper-

ties of copper compounds are largely

dependent on the amount of Cu2+

in so-

lution (Scheck & Pscheidt, 1998). Man-

cozeb may also chelate copper ions,

making them more available at those

sites in bacterial cells that are detrimen-

tally affected by copper (Medhekar and

Boparai, 1981).

For one strain of X. axonopodis pv. vesi-

catoria, P635, even the addition of man-

cozeb to copper hydroxide suspensions

did not reduce bacterial populations to

desirable levels. Populations were still

above 1 x 106 CFU/ml after 2 hr expo-

sure in vitro. These observations may

help explain the often suboptimal per-

formance of copper applications to

commercial pepper and tomato crops in

Florida even when copper/maneb or

copper/mancozeb tank mixes are used.

Strains with this level of resistance may

be responsible for outbreaks of bacterial

spot when no amount or frequency of

copper/maneb (mancozeb) seems to

control the disease.

Mancozeb and Tanos® did not have a

direct toxic effect on the bacterial strains

in this study. The reports of disease sup-

pression with Tanos® apparently are not

the result of bactericidal activity but

might be due to another mode of action

such as systemic acquired resistance

(Kessmann et al., 1994; Lawton et al.,

1996).

Copper/mancozeb sprays when applied

twice before and periodically after in-

oculations provided better control than

copper alone in our greenhouse experi-

ments. It has been known since the

1960’s and was reported fully for the

first time in 1981 (Conover and Gerhold,

1981), that this tank mix is more effica-

cious than copper alone for controlling

bacterial diseases of vegetables. The ad-

63

vantages of using maneb or mancozeb

with copper have been confirmed in nu-

merous trials since (Adaskaveg and

Hine,1985; Conlin and McCarter,1983;

Jones and Jones, 1985; Kousik et al.,

1996; Marco and Stall, 1983; McCarter,

1992; McGuire, 1988; Pernezny and

Collins, 1997; and Scheck and Pscheidt,

1998).

The antibiotic kasugamycin (formulated

as Kasumin 2 L) looked promising for

control of bacterial spot in several ex-

periments. Kasugamycin is not currently

used in the United States, but tolerances

have been established for residues on

tomatoes and peppers imported from

Mexico (Anonymous, 2005). Mexican

growers are targeting principally X. ax-

onopodis pv. vesicatoria when applying

kasugamycin to the two crops. Because

kasugamycin is active only against phy-

topathogens, it has never been used for

medical or veterinary purposes (Anony-

mous, 2005). Thus, there is less concern

about its use in the agricultural sector

that that associated with streptomycin,

tetracycline, and other antibiotics within

the current medical/veterinary arsenal.

Studies on kasugamycin, including com-

binations or rotations with copper com-

pounds, could prove fruitful in strength-

ening integrated disease management

programs for tomato and pepper. Regis-

tration of kasugamycin in the United

States would provide Florida growers

with a much-needed tool already avail-

able to their market competitors in

Mexico.

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Copper tolerance and zinc sensitivity of

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Andersen, G.L., Menkissoglou, O., and

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properties of copper-tolerant strains of

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Anonymous 2005. Pesticide fact sheet:

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Colin, K.C., and McCarter, S.M. 1983.

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1991. Copper-and-streptomycin-resistant

strains and host-differentiated races of

Xanthomonas campestris pv. vesicatoria

in North Carolina. Plant Dis. 75:733-

736.

Scheck, H.J., and Pscheidt, J.W. 1998.

Effect of copper bactericides on copper-

resistant-and-sensitive strains of Pseu-

domonas syringae pv. syringae. Plant

Dis. 82: 397-406.

Stall, R.E., Loschke, D.C., and Jones,

J.B. 1986. Linkage of copper resistance

and avirulence loci on a self-

transmissible plasmid in Xanthomonas

campestris pv. vesicatoria. Phytopathol-

ogy 76:240-243.

65

Table 1. Strains of three vegetable bacterial pathogens classified as resistant or tolerant to

copper on two laboratory agar media y

.

No. strains resistant onz

Pathogen Host of

origin

No.

strains

tested GNA + Cu CYE + Cu

Xanthomonas campestris pv.

vitians

Lettuce 19 0 0

Xanthomonas axonopodis pv.

vesicatoria

Pepper 36 34 0

Xanthomonas axonopodis pv.

vesicatoria

Tomato 39 39 0

Total 94 73 0

y Evaluation of resistance based on visual estimates of growth on copper-containing me-

dia compared to growth on control plates without copper amendment. Three replicate

plates (10 sweeps/plate) of each agar/strain combination were rated in two experiments

with the same results.Z Medium tested were glucose-nutrient agar (GNA) + Cu (CuSO4 · 5 H2O, 200 g/ml),

casitone yeast extract agar (CYE) + Cu (CuSO4 · 5 H2O, 161 g/ml and 200 g/ml CuSO4 ·

5 H2O).

66

Table 2. Populations of representative strains of plant-pathogenic bacteria of after 2-hr

exposure to copper-based and other agrichemicals v

.

Log10 Populationz

Strainw

Qualitative

reactionx

Treatmenty

Exp. 1 Exp. 2

Xanthomonas campestris

pv. vitians, L7

GNA-sen.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.21 a

8.42 b

8.21 a

0 c

0 c

Xanthomonas campestris

pv. vitians, L11

GNA-sen.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.94 a

8.43 b

8.26 c

3.63 d

0 e

8.67 a

8.45 ab

8.18 b

4.88 c

0 d

Xanthomonas campestris

pv. vesicatoria, P637

GNA-sen.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.29 a

8.16 b

8.56 c

3.66 d

4.28 c

8.31 a

8.34 a

8.29 a

3.65 b

3.63 b

Xanthomonas campestris

pv. vesicatoria, P635

GNA-res.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.72 a

8.68 a

8.81 b

8.69 a

6.72 c

8.10 a

8.07 a

8.06 a

8.83 b

6.90 c

Xanthomonas campestris

pv. vesicatoria, T135

GNA-res.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.46 a

8.29 b

8.34 b

8.00 b

0 c

8.53 a

8.18 b

8.10 c

8.30 d

0 e

Xanthomonas campestris

pv. vesicatoria, T193

GNA-res.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.57 b

8.89 a

8.32 c

8.42 c

4.40 d

8.55 a

8.05 bc

8.04 c

8.16 b

3.68 d

Xanthomonas campestris

pv. vesicatoria, P648

GNA-res.

CYE-sen.

Control (H2O)

Tanos

Mancozeb

Copper hydroxide

Cu + Mn

8.46 a

8.29 b

8.34 b

8.00 b

0 c

8.53 a

8.18 b

8.10 c

8.30 d

0 e

67

vApproximately 2x10

8 CFU/ml of suspension of each strain exposed for 2 hr to equal

volume of agrichemicals in the laboratory at dosages equivalent to those used in com-

mercial fields. Data are mean of 3 replicate serial dilution samples for each treatment.wL strains are from lettuce, P strains from pepper, and T strains from tomato. All strains

were originally isolated form diseased plants in commercial fields in Florida.XGNA= glucose-nutrient-agar. CYE= casitone/yeast extract agar. Sen. = sensitive in

qualitative assay. Res. = resistant in qualitative assay.yTanos is a trade name for a product consisting of a pre-packaged mixture of famoxadone

and cymoxanil. Cu+ Mn is an on-site prepared mixture of copper hydroxide and man-

cozeb.zMeans in a column for a given strain not followed by the same letter are statistically dif-

ferent according to Waller-Duncan’s k-ratio t-test mean separation procedure, P 0.05. A

value of 1 was added to all raw population data to overcome the value of log10 0 as unde-

fined. F-statistic was significant at P 0.0001 in each experiment.

Table 3. Control of bacterial spot of pepper incited by copper-resistant strain P635 in the

greenhouse with copper-based bactericidesx

Exp. 1 Exp. 2

Treatment13 DAI

y 20 DAI 10 DAI 14DAI

Control (H2O) 17.8 az

21.0 a 38.9 a 53.3 a

Copper hydroxide 11.8 b 11.2 b 34.0 a 46.3 a

Mancozeb 3.8 c 4.4 c 38.3 a 51.0 a

Copper hydroxide+mancozeb 1.7 c 2.0 c 25.4 b 31.9 bx Numbers are means of ratings of disease as the percentage of leaf surface covered by

lesions combined with that lost from the plant due to premature defoliation. Experiments

were a nested design with three pepper plants nested within each treatment and treat-

ments arranged randomly within three blocks.y DAI = Days after inoculation

z Means within a column followed by the same letter are not significantly different based

on Waller-Duncan’s mean separation procedure at P 0.05.

68

Table 4. Control of bacterial spot of pepper incited by copper-resistant strain P635 in the

greenhouse with newer, novel compoundsx.

Exp. 1 Exp. 2

Treatment 13 DAIy

20 DAI 7 DAI 14DAI

Control (H2O) 40.0 az

29.1 a 35.6 a 35.0 b

Physpe seaweed derivative 38.1 a 25.2 a 41.8 a 46.7 a

Actinovate biological 34.8 a 25.3 a 35.0 a 33.5 b

Tanos + Kocide + ProPhyt a/w

Kocide + mancozeb + ProPhyt 3.3 c 4.6 c 27.7 b 28.3 bc

Kasugamycin 24.8 b 16.2 b 15.2 c 15.0 b

Kocide + mancozeb 3.1 c 3.7 c 22.3 b 22.3 cx Numbers are means of ratings of disease as the percentage of leaf surface covered by

lesions combined with that lost from the plant due to premature defoliation. Experiments

were a nested design with three pepper plants nested within each treatment and treat-

ments arranged randomly within three blocks.y DAI = Days after inoculation

z Means within a column followed by the same letter are not significantly different based

on Waller-Duncan’s mean separation procedure at P 0.05.

69

Table 5. Control of bacterial spot of tomato in the greenhouse, caused by Xanthomonas

axonopodis pv. vesicatoria (strain T193, race 3) with copper and copper/mancozeb tank

mixy.

Disease Rating (%)

Treatment June 20 June 26 June 30

Control (water) 12.2 az 14.9 a 17.0 a

Kocide 6.8 b 11.0 a 9.3 b

Mancozeb 8.1 b 11.6 a 10.7 b

Kocide + mancozeb 7.1 b 8.6 c 6.11 c

y Data are based on a greenhouse experiment arranged in a nested design with 3 individ-

ual tomato plants (BHN 586), nested within each of 3 blocks and each treatment repli-

cated once within a block. Plants were sprayed twice at a 10-day interval before appli-

cation and one after inoculation with a 1x107 CFU/ml suspension of X. axonopodis pv.

vesicatoria (T193, race 3) previously shown to be resistant to copper. Plants were sub-

sequently rated 7, 13 and 17 days after inoculation.z Means within a column followed by the same letter are not significantly different based

on Waller-Duncan’s means comparison at P < 0.05.

Table 6. Control of bacterial spot of tomato repeat in the greenhouse, caused by X. ax-

onopodis pv. vesicatoria (T193, race 3), with copper and copper/maneb tank mixy.

Disease Rating (%)

Treatment June 20 June 26

Control (water) 17.2 az 21.4 a

Kocide 5.2 b 11.0 b

Mancozeb 6.9 b 10.2 b

Kocide + mancozeb 4.9 b 10.2 b

y Data are based on a greenhouse experiment arranged in a nested design with 3 individ-

ual tomato plants (BHN 586), nested within each of 3 blocks and each treatment repli-

cated once within a block. Plants were sprayed twice at a 10-day interval before appli-

cation and one after inoculation with a 1x107 CFU/ml suspension of X. axonopodis pv.

vesicatoria (T193, race 3) previously shown to be resistant to copper. Plants were sub-

sequently rated 14 and 18 days after inoculation.z Means within a column followed by the same letter are not significantly different based

on Waller-Duncan’s means comparison at P < 0.05.

70

Characterization of the Phytophthora

Infestans Population Present

in Florida

Dr. Pamela Roberts

Dr. Diana Schultz

Plant Pathology, SWFREC/IFAS, Uni-

versity of Florida,

2686 SR 29 N.

Immokalee, Fl, 34142.

Cooperator:

Dr. Charles Mellinger

Glades Crop Care, Inc.

949 Turner Quay

Jupiter, FL 33458.

Abstract. Late blight, caused by Phy-

tophthora infestans, affects tomatoes and

potatoes in Florida during the winter-

spring crop season. A late blight re-

search project was initiated at the

Southwest Florida Research and Educa-

tion Center in order to provide the serv-

ice of characterizing the P. infestans pre-

sent in the field, as a tool to redirect the

grower control measures. In 2005, iso-

lates of P. infestans were very aggres-

sive in the field and difficult to control

even with an intensive fungicide spray

program. In contrast, although the 2006

outbreak was widespread, the isolates

were not as aggressive as the 2005 iso-

lates and less damage was reported. Iso-

lates of P. infestans from these two

growing seasons were characterized for

mating type, GPI, PEP, RG57-RFLP

(2005 only), and mitochondrial haplo-

type and fungicide sensitivity tests. The

isolates of P. infestans present in central

and south Florida were difficult to iso-

late in culture and several different me-

dia and amendments were evaluated to

increase in the recovery of P. infestans.

Isolates from the 2005 outbreak shared

identical profiles by mating type, GPI,

PEP, RG57-RFLP, and mitochondrial

haplotype. In fungicide sensitivity as-

says, all 2005 isolates were sensitive to

mefenoxam except one which exhibited

intermediate resistance. In 2006, no iso-

lates were recovered which were identi-

cal to the 2005 isolates. Isolates in 2006

exhibited a greater range in response to

mefenoxam from sensitive to resistant.

The isolates tested from the two growing

seasons are the same within a season but

are very different across seasons. Char-

acterization of the isolates, particularly

fungicide sensitivity, should be per-

formed at the onset and throughout the

outbreak in order to make management

recommendations to growers. The vari-

ability of US-types across seasons and

lack of detection of the previous sea-

son’s genotype may indicate lack of sur-

vival from season to season and intro-

duction of inoculum in this growing area

each year.

Introduction. In the 2004-05 growing

season, late blight (Phytophthora in-

festans) on tomato was very difficult to

control even with a very intensive, ex-

pensive, fungicide application schedule.

Isolates were sent out-of-state for char-

acterization of race, mating type, and

mefenoxam sensitivity. Isolates were

mefenoxam sensitive, a dramatic change

from the previous years when isolates

were resistant. This information was

used to make fungicide recommenda-

tions. In 2006, although the outbreak

was widespread, the isolates were not as

aggressive as the 2005 isolates and less

damage was reported. The grant from

the Tomato Committee in 2005-current

funded this lab to establish the labora-

tory resources in Florida to perform the

above characterizations in a timely man-

ner. The tests targeted were to perform

genotyping, mefenoxam sensitivity, and

71

mating type. Some of these tests require

isolation of P. infestans in pure culture

using selective media amended with

fungicides and antibiotics. The mating

type is determined by crossing known

A1 and A2 mating types with unknown

isolates. Sensitivity to phenylamide fun-

gicides (mefenoxam) can be assayed by

growing the pathogen on agar plates

amended with the fungicide. Molecular

assays such as the cellulose acetate elec-

trophoresis (CAE) method are used to

determine genotypes using field sam-

ples. Allozyme assays for the glucose-6-

phosphate isomerase (Gpi) and peptidase

(Pep) loci allow identification of the

most common US clonal genotypes (US-

types). This type of information can be

applied to understand the characteristic

of the pathogen in the field and used for

selecting management options. Our lab

successfully implemented the above tests

with increasing efficiency as our experi-

ence in working with P. infestans and

conducting the various tests increased.

The original objectives as proposed were

to characterize the population of P. in-

festans in Florida on tomato in the 2005-

06 season as follows:

1. Collect samples representative of

the P. infestans population causing dis-

ease on tomato and potato, to a lesser

extent, in Florida in 2005-06 season.

Isolates were recovered from tomato and

potato in spring 2005 and are stored. The

isolates from the previous season will be

compared to the isolates recovered in the

upcoming seasons.

2. Characterize the isolates for

mating type, allozyme profile (for race

identification) and resistance to me-

fenoxam. Our goal is to be able to pro-

vide the allozyme race profile from field

samples as quickly as Dr. Weingartner,

now retired and advising us, did previ-

ously. We have arrangements to receive

standard race and mating types repre-

sentatives from a P. infestans collection

to use as standards in our tests.

3. Determine pathogenicity and ag-

gressiveness of the isolates by tomato,

potato, and other host inoculations.

Materials and methods.

Sampling. Isolate collections were initi-

ated when the disease was first reported

in the field and continued until late

blight was either no longer in the field or

the season terminated. Samples were

obtained by field visits, submission from

collaborators or other sources.

Pathogen recovery. Isolations were

made from sporulating leaves or stems

by inoculating to tomato tissue or by

placing the sporangia and/or mycelia

plus sporangia directly onto several cul-

ture media: Rye B agar, Potato dextrose

agar, Barley-Potato dextrose agar, Mac-

Conkey and V8 juice media amended w/

antibiotics or fungicides (ampicillin, ri-

fampicin, mymexasol, pymaricin and

pentachlor-nitro-bencene). For all media,

the Van Tiegham-cell method of puri-

fying fungi was used.

Sensitivity to mefenoxam. Sensitivity

to mefenoxam (Ridomil Gold®) was

tested by adding the fungicide to 10%

clarified V8 culture media at test con-

centrations of 0 (control), 5 and 100

g/ml. Resistance was determined based

on growth of the colony compared to the

control, and resistant and intermediate

sensitivity was calculated as 40% growth

of the control.

Allozyme profile for US-typing. Spo-

rangia and mycelia for the cellulose

72

acetate electrophoresis (CAE) were har-

vested directly from the samples re-

ceived after overnight incubation in

moist chamber. For confirmation, CAE

was repeated after obtaining pure cul-

tures grown on artificial media. Samples

were electrophoresed on CAE gels and

stained for GPI and PEP profiles and

compared to known US-type isolates for

identification.

Mating type. Mating type tests were

conducted by placing a 5 mm agar disk

from 2-wk old unknown isolate in a 6

cm petri-dish containing 10% clarified

V8 media, and a known A1 or A2 type

isolate of P. infestans on the opposite

side of the same plate. Oospore forma-

tion was examined at 10 days after plate

inoculation.

Mitochondrial haplotype. DNA sam-

ples were extracted from pure cultures

and subjected to PCR analysis in combi-

nation w/restriction analysis (PCR-

RFLP).

Pathogenicity and aggressiveness of

isolates. Virulence tests were performed

on tomato detached leaf. Leaflets were

collected from growth chamber grown

tomato plants (FL 47) from the upper

fully expanded leaves, and placed in a

moist chamber. Two leaflets per plate

were placed abaxial side up, and inocu-

lated with 10 l of 1x104 zoospores per

ml. Inoculated leaflets were kept in an

incubator at 18 C and 14/10 hr light cy-

cle. Tests were also conducted on

growth-chamber grown tomato plants.

Inoculated plants were kept in the

growth chamber, at disease favorable

conditions and 100 % humidity. Disease

development was recorded 7 days after

inoculation.

Results. We successfully collected and

characterized P. infestans isolates in

both 2005 and 2006 spring seasons even

though the isolates were very difficult to

recover on culture media. For several of

the characterization tests, it is necessary

to obtain P. infestans in pure culture.

Culture medium which had previously

worked well to recover P. infestans was

not effective for these isolates. There-

fore, several artificial culture media were

evaluated for recovery and maintenance

of P. infestans. The culture media that

offered the best recovery rate was Bar-

ley-Potato dextrose agar amended with

_sitosterol. The incubation temperature

which gave the best results was 18-20 C

in the dark. In order to keep the isolates

on samples alive while the media tests

were conducted, isolates were inoculated

and maintained on tomato plants.

Isolates were characterized for tentative

US-type through GPI and PEP profiles,

mating type, mefenoxam sensitivity and

mitochondrial haplotype (Table 1). The

collected samples were homogeneous

within a year and but greatly different

between years. All 2005 isolates

matched the US-13 type for GPI and

PEP, A2 mating type, and sensitive to

mefenoxam except one that responded as

intermediate. The 2006 isolates matched

the US-14 type, A2 mating type, and

ranged in response to mefenoxam, from

very sensitive to resistant. Early in the

season, variation in the GPI profile was

observed among the 2006 isolates, how-

ever, by the end of the season the profile

described below was dominant.

73

Table 1. The typical profile for 2005 and 2006 isolates are presented here.

2005 2006

Mating Type A2 A2

GP1 100\100 100\122

PEP 100\100 100\100

RG57 DNA fingerprint 1,3,5,7,10,13,14,16,18,20,21,24,25* NA**

US-Type US-13 US-14

Mitochondrial haplo-

type

Ia NA**

Mefenoxam sensitivity S; I S;I;R

* Some isolates were sent to Dr. Deahl’s Lab at USDA Beltsville, Maryland in exchange

for some of the US-type standard isolates and for the RG57 fingerprinting.

** RG57 DNA fingerprint and mitochondrial haplotype data for the 2006 isolates are not

yet available (NA) but will be conducted soon.

Virulence and pathogenicity tests per-

formed on tomato confirmed the field

information suggesting that the 2005

isolates were more aggressive than the

2006 (Figure 1). Sporangia and zoospore

production and growth on plants were

noticeably greater in the 2005 isolates

compared to the 2006 isolates tested.

Unfortunately, due to the loss of our

greenhouse facilities to Hurricane

Wilma, we were limited in the capability

to perform extensive pathogenicity and

virulence tests on hosts other than to-

mato.

Conclusions. Our lab at SWFREC now

has the capability of testing P. infestans

isolates for US-type (mating type,

haplotype, GPI and PEP), virulence and

mefenoxam sensitivity. As our experi-

ence increased with performing the tests

and handling the P. infestans samples,

the tests were completed with increasing

efficiency, taking less time to conduct.

One major concern was communicating

our findings to clientele as quickly as

possible and we hope to decrease the

time to respond in upcoming seasons.

The results of these studies are signifi-

cant with regards to determining the

source of the epidemic and use of fungi-

cides. The isolates from the two growing

seasons are the same within a season, but

are very different across seasons. This

variability of US-types across seasons

and lack of detection of the previous

season’s genotype, may indicate lack of

survival of P. infestans in Florida from

season to season and introduction of in-

oculum in this growing area each year,

as previously thought. The variability of

the isolates across seasons also makes it

impossible to predict future types from

results attained the previous year. The

difference in mefenoxam sensitivity of

the isolates in these tests between the

two years is also significant as this fun-

gicide was recommended during the

growing season when sensitivity was

detected. However, the presence of re-

sistant isolates in 2006 means that this

fungicide should not have been used as

soon as these isolates were detected.

Characterization of the isolates, particu-

larly fungicide sensitivity, should be per-

formed at the onset of late blight and

throughout the entire season in order to

74

make management recommendations to

growers.

Of particular future interest will be the

identification of the source(s) of the in-

oculum in order to determine why the

genotypes change yearly and whether we

can predict which one will appear and,

secondly, to continue characterization of

the population in future years.

Figure 1. Pathogenicity tests. Fl47 tomato plants were inoculated with 103 sporangial

suspension. Two representative isolates from 2005 and two from 2006 are presented.

Isolates 2005Isolates 2006

75

Evaluating Factors Affecting Movement

of the Silverleaf Whitefly and Tomato

Yellow Leaf Curl Virus

David J. Schuster

Craig D. Stanley

University of Florida/IFAS

Gulf Coast Research & Education Center

5007 60th Street East

Bradenton, FL 34203

Jane E. Polston

Plant Pathology Department

University of Florida

Gainesville, FL 32611

Sabine Grunwald

Soil and Water Science Department

University of Florida

Gainesville, FL 32611

Abstract. Commercial SLWF and TYLCV

scouting data were obtained for 26 farms for

the spring and fall seasons of 2005 covering

a large portion of the Palmetto-Ruskin to-

mato production area. The data were aver-

aged for each block or planting date for each

farm for each sampling date and were en-

tered into a computer database. Commercial

scouting data for SLWF and TYLCV were

collected for a single tomato farm in the

Ruskin area in the spring of 2006. One sam-

ple was taken twice weekly for every 2 acres

and each was geo-referenced with global

positioning system (GPS) coordinates. The

data were downloaded into a computer and

then merged into a single file for the entire

season. The data for 2005 or 2006 have not

been analyzed.

Introduction. The silverleaf whitefly

(SLWF), Bemisia argentifolii Bellows &

Perring, remains the key insect pest of to-

mato in Florida since 1988. Although the

insect causes damage by inducing the ir-

regular ripening (IRR) disorder of tomato

fruit, the most severe damage occurs by the

transmission of geminiviruses, particularly

Tomato yellow leaf curl virus (TYLCV). To

avoid the losses, particularly due to TYLCV,

100% of the tomato transplant and field

growers are applying imidacloprid (as Ad-

mire Pro™) or thiamethoxam (as Plati-

num™), primarily as drenches. The soil ap-

plications at transplanting provide systemic

control of nymphal populations of the sil-

verleaf whitefly for eight to 12 weeks, de-

pending upon location and season. As the

controlling affects of these insecticides di-

minishes, growers apply alternative chemis-

tries, such as the insect growth regulators

buprofezin (Courier™) and pyriproxyfen

(Knack™), in order to continue controlling

whitefly nymphs and, thereby, to avoid ir-

regular ripening. However, because of the

threat of early infection by TYLCV, all

growers are applying broad spectrum insec-

ticides when whitefly adults appear in the

fields, even during the time of peak nymphal

efficacy of imidacloprid and thiamethoxam.

Despite these aggressive measures, the inci-

dence of TYLCV has remained high. In west

central Florida in the spring of 2006, a wide-

spread outbreak of TYLCV occurred despite

numerous applications of insecticides.

Current Geographical Information System

(GIS) technology allows much flexibility in

the use and analysis of collected data that is

linked to specific geographical locations.

This allows “layering” of the data with other

mapped and stored information (land use,

soil types, weather measurements, demo-

graphic information, etc.) to permit a spatial

analysis and subsequent visual presentation

of the analysis that can provide much infor-

mation toward understanding and solving a

problem. A GIS-based analysis of whitefly

populations and distribution with subsequent

TYLCV incidence at specific locations in a

region or even at specific locations within a

particular production field would provide

opportunities for determination of potential

source locations, direction of disease pro-

gression, and impact of any cultural prac-

tices or control measures implemented. Be-

cause querying and analysis of the data can

be done in many ways, these analyses have

76

the potential to provide valuable information

for an understanding of the problem and for

developing new strategies for minimizing

the likelihood or the severity of future out-

breaks.

Materials and Methods. Commercial

scouting data for SLWF adults and nymphs

and TYLCV incidence and severity that was

collected over a large area in the Palmetto-

Ruskin tomato production area was obtained

for the spring and fall seasons of 2005. The

area was represented by 13 tomato farms in

each season. The data were averaged for

each block or planting date for each farm for

each sampling date and were entered into a

computer database.

One commercial tomato farm in the Ruskin

area was sampled more intensively during

the spring of 2006. One sample was taken

twice weekly for about every 2 acres. Data

for SLWF adults and nymphs and for per-

cent of plants with symptoms of TYLCV

were entered onto a data logger. Each sam-

ple site for each sampling date was geo-

referenced with global positioning system

(GPS) coordinates. The data were down-

loaded into a computer and then merged into

a single file for the entire season. Spray and

land use records and weather records are

being obtained.

Results. The data for 2005 or 2006 have not

been analyzed. The individual blocks or

planting ages in 2005 still need to be geo-

referenced using GPS. In addition, the virus

severity data were not reported consistently

in 2005, so a standardized scale or system

needs to be developed before the data can be

analyzed. Spray, land use, and weather re-

cords are being obtained to help explain

changes in whitefly densities and TYLCV

incidence.

A technical support person has been identi-

fied to begin analyzing the data using differ-

ent spatial analysis techniques and proce-

dures within GIS. The resulting graphical

output of the analyses of the 2005 and 2006

data will be used to determine which analy-

sis techniques and procedures are best suited

for studying the spread of the SLWF and

TYLCV. The data will also be examined for

intra- and inter-farm relationships in order to

determine whether area-wide sampling can

be by blocks within farms or whether sam-

pling will need to be by samples within

blocks within farms.

77

Implications of a Change in Carton

Size for Fresh Tomatoes from 25

pounds to 10 Kilograms

John J. VanSickle and Evan Shinbaum1

Abstract. The State of Florida is a major

producer of fresh market tomatoes for

the U.S. market. The Florida Tomato

Committee has the responsibility of es-

tablishing quality regulations for fresh

market tomatoes sold from its regulated

area, including allowable carton size.

These regulations would also apply to

imported tomatoes during the marketing

period of Federal Marketing Order 966.

These regulations are one tool used to

maintain an orderly market for fresh

market tomatoes. An analysis of a pro-

posed change in carton size from 25

pounds to 10 kilograms was performed

to estimate the effects of this change.

The results indicate that such a change

would benefit packer/shippers from the

additional fees collected for packing and

selling tomatoes, but that benefits to

growers are dependent on how

packer/shippers distribute increased re-

turns from buyers.

Introduction. The State of Florida is a

major producer of fresh tomatoes for the

U.S. market. The marketing of most to-

matoes grown in Florida comply with

regulations imposed under the authority

of Federal Marketing Order 966. The

Florida Tomato Committee, which gov-

erns the marketing order, maintains that

regulations are necessary to maintain

orderly market conditions. Although

many regulations are met with some de-

gree of skepticism, market standardiza-

tion has been credited with improving

1Professor and Graduate Student, Food & Re-

source Economics Department, IFAS, University

of Florida

grower returns and maintaining a reli-

able quality of tomatoes for consumers

at a reasonable price. One of the tools

for maintaining standards is the designa-

tion of the carton size in which fresh

market tomatoes can be shipped.

The tomato carton has changed signifi-

cantly since the beginning of Federal

Marketing Order 966. Mature green to-

matoes were shipped in 60 pound con-

tainers prior to a change to 40 pound

containers in the 1959/60 season. An-

other change took place in the 1970/71

season that lowered the size of the carton

to 30 pound containers. The last change

in box size occurred in the 1980/81 sea-

son when shippers began packing mature

green tomatoes in 25 pound containers.

Growers considered lowering the size

again to 20 pound containers in the late

1980’s (VanSickle and Castejon, 1990),

but chose not to when estimates sug-

gested that such a change would not be

beneficial to growers.

A change in box size to a smaller con-

tainer will add costs in the handling of

fresh market tomatoes. A reduction in

size from 25 pounds to 10 kilograms will

result in 13.3 percent more containers

being packed, transported and handled

for the same weight volume. The per-

ceived benefit will be derived from an

improvement in quality that reaches the

end user and in reduction of losses as

they are packed in smaller containers.

Several studies have reported on losses

incurred in the tomato industry due to

decay during handling. In 1965, U.S.

losses were estimated to be $13.7 mil-

lion annually in product value alone

(USDA, 1965). Jordan et al. (1986) re-

ported that damage to tomatoes was a

major factor, which lowers the price re-

78

ceived by growers. The importance of

carton size can be seen in the current dif-

ferentiation in carton size for mature

green and vine ripe tomatoes. Mature

green tomatoes are generally volume

packed in standard 25 pound containers.

Vine ripe tomatoes are often place

packed and generally packed in 20

pound containers to maintain quality

since they are more susceptible to dam-

age during packing and post packing op-

erations.

Several agents stand to be impacted by a

change in carton size. Growers will

benefit from increased values realized as

quality improves at the handler and con-

sumer levels. Handlers would be more

willing to pay more for tomatoes be-

cause of lower costs resulting from

fewer losses and more efficient market-

ing. These increased revenues will be

countered with increased costs of pack-

ing and selling. There will be increased

packing and selling fees from the addi-

tional cartons that will be required for

smaller cartons.

Packer/shippers will be impacted by a

smaller carton since they will have to

pack more boxes throughout the season

to sell the same weight volume. Packers

may realize more revenue because they

charge growers for packing by the car-

ton, and charge buyers for palletizing

and gassing by the carton.

Packer/shippers will also incur increased

costs, because of the need to add capital

equipment and personnel if they cur-

rently operate at or near capacity.

Wholesalers and retailers will also be

impacted by changes in box size. They

will handle more cartons which will in-

crease handling costs and fees charged

by packer/shippers for services they pro-

vide (e.g., palletizing and gassing).The

benefit that would be expected by retail-

ers in making this change will be in

lower costs resulting from improved

quality and less loss of product, and

from increased prices resulting from

higher quality product being sold to con-

sumers.

Finally, consumers will be impacted

with higher prices for products they buy.

Costs will increase in the handing sys-

tem if the smaller carton does not result

in fewer losses of physical product.

Some of these costs will be passed on to

consumers. Conversely, if a smaller

carton results in fewer physical losses of

product, then some of those savings are

also likely to be passed on to consumers.

Consumers will also benefit from any

improvement in quality that this change

could bring. They will be more likely to

pay more for tomatoes if this improve-

ment occurs.

Methods. The objective of this research

was to estimate the economic implica-

tions of a change in carton size for ma-

ture green tomatoes from 25 pounds per

carton to 10 kilograms per carton. The

focus is on implications to growers and

packer/shippers, even though wholesal-

ers, retailers and consumers are also

likely to be impacted.

The procedure used to estimate eco-

nomic impacts from a change in the

carton size for Florida fresh tomatoes

was to divide the analysis into the

grower and shipper/packer sectors. The

impact on growers was estimated using

an analysis of the additional costs ex-

pected from packing 13.3 percent more

containers and relating that to the re-

quired increase in price that would be

necessary to offset those added costs.

79

The impact on packer/shippers was es-

timated by budgeting the effect a change

in box size would have on the revenues

received by packer/shippers in the

packing and marketing of fresh toma-

toes. These changes in revenues are

compared to the additional costs that

may be required to expand the capacity

of the packinghouses.

Results and Discussion.

Growers. A change in carton size from

25 pounds to 10 kilograms will require

additional costs in packing and selling of

fresh tomatoes. Growers are expected to

share in this added cost. A change in box

size to 10 kilograms for mature green

tomatoes will lead to an increase of 13.3

percent in boxes packed. Packing and

selling fees published by Smith and

Taylor (2005) ranged from $2.59 per

carton in the Manatee Ruskin area to

$2.79 per carton in the Dade County

producing area. Assuming a packing and

selling fee of $2.70 per carton, if per

carton fees do not change, then the

packing and selling fees will increase

from 10.8 cents per pound to 12.25 cents

per pound, an increase of $0.3625 per 25

pound equivalent carton.

The impact a change in carton size could

have on price was estimated by Van-

Sickle and Castejon in 1990 by examin-

ing the impact the change in carton size

from 30 to 25 pounds had in the 1980/81

production season. Their analysis used

an econometric model to estimate the

increase in price that had been realized

since the carton changed from 30 pounds

to 25 pounds. Their model estimated an

increase in price of $0.328 per 25 pound

carton equivalent. The reported increase

in the cost of packing and selling toma-

toes from the 1980/81 season to the

1981/82 season was $0.397, $0.238,

$0.288 in the Dade County, Southwest

Florida and Ruskin producing areas, re-

spectively. These results suggest that

Dade County growers were worse off

after the change in box size while grow-

ers in the Southwest Florida and Ruskin

producing areas received marginal bene-

fits.

Unless a change in box size addresses a

critical post harvest issue, it is doubtful

that growers would benefit from this

change, unless benefits realized at other

levels of the marketing channel are

passed on to growers. It appears that

changes in returns to growers were

mixed when the box size was changed

from 30 pounds to 25 pounds in 1981.

Growers will have to share in other

benefits to expect any benefits from a

change to a smaller carton.

Packer/Shippers. A change in carton

size from 25 pounds to 10 kilograms will

create the need to pack an additional

13.3 percent more boxes than previously

packed for the same weight volume.

This increase will create additional reve-

nues for packer/shippers since most of

their services are billed on a per carton

basis. An increase in the number of car-

tons may also create a need for addi-

tional capacity in packinghouses, in-

creasing their costs for equipment and

labor.

Data from the 1980/81 and 1981/82 sea-

sons indicates that packers increased

their per pound packing and selling fees

to growers by a range of 13.2 percent to

23.6 percent after the change in box size.

Per carton gassing and palletizing fees

did not change, indicating an increase of

16.7 percent for those services. Total

revenues realized by packers increased

80

$0.39, $0.25 and $0.26 per 25 pound

equivalent in the Dade County, South-

west Florida and Ruskin producing ar-

eas, respectively.

VanSickle and Castejon (1990) esti-

mated the increased investment that

would be necessary by packer/shippers

to handle the additional volume of car-

tons that would be required if cartons

were changed from 25 pounds to 20

pounds. They budgeted capital additions

in the packinghouse, including a set-up

machine, 3 filler machines and a pallet-

izer. Annualized out, they estimated that

the packinghouse would realize $62,700

in additional annual costs from expan-

sion required to pack the additional

boxes (costs included in this estimate

included depreciation, capital and added

employee expense).

Assuming that the average increase in

revenues from a change in carton to the

10 kilogram size is $0.30 per 25 pound

equivalent carton, then the investment

required (annualized considering depre-

ciation and capital cost) by packers to

absorb the required added capacity (13.3

percent more boxes packed) would need

to be less than $300,000 per year for a

packinghouse currently packing

1,000,000 cartons.

Transportation. VanSickle and Caste-

jon (1990) also estimated that changing

the carton size from 25 pounds to 20

pounds would result in shipping costs

increasing by 11.1 percent. This conclu-

sion was reached because trailers used to

haul tomatoes were expected to hold

11.1 percent fewer pounds of tomatoes

because the standard trailer in 1990

could not hold all the boxes that would

be required for the same volume of to-

matoes shipped in 25 pound cartons.

They estimated that a standard trailer

held 40,000 pounds of tomatoes with a

truck-load of 20 pallets, each pallet

holding 80 boxes which hold 25 pounds

each. Accounting for the pallets and

boxes, the total truck weight in cargo

was estimated at 45,800 pounds.

Changing to a smaller carton to accom-

modate 20 pounds of tomatoes was esti-

mated to result in only 36,000 pounds of

tomatoes in a truckload (20 pallets with

90 boxes each) with a total cargo weight

(tomatoes, cartons and pallets) of 42,400

pounds.

Discussions with industry representa-

tives suggest that this constraint would

not hold in changing from a 25 pound

carton to a 10 kilogram carton. There

appears to be sufficient space in trailers

currently hauling tomatoes to hold the

same capacity, i.e., increasing the car-

tons packed in a truckload by 13.3 per-

cent. No transportation impact is ex-

pected in changing to a 10 kilogram

carton.

Conclusions. Changing the carton from

a standard 25 pound carton to a 10 kilo-

gram carton would likely benefit

packer/shippers. The analysis contained

here suggests that packer/shippers could

increase revenues for gassing and pal-

letizing by 13.3 percent if they are able

to hold the per carton gassing and pal-

letizing fees fixed at current levels. That

was the case when the previous box

change occurred in 1981.

Packer/shippers also increased their

revenues by $0.25 to $0.39 per 25 pound

carton equivalent for packing and selling

fees collected from growers following

the decrease in box size in 1981. The

study completed by VanSickle and

Castejon (1990) suggests that growers

were rewarded with additional revenues

81

of $0.328 per carton in higher prices per

carton to offset the increased packing

and selling fees. Combined, the total

revenues coming back to growers and

packer/shippers more than offset the in-

creased costs at the grower and

packer/shipper levels, roughly equal to

the amount of increased gassing and

palletizing fees collected from buyers,

with the packer/shippers realizing most

of that gain.

A change in the carton to a 10 kilogram

carton could have similar results. Grow-

ers would be expected to pay more for

packing and selling fees. Pack-

ers/shippers could again benefit from an

increase in gassing and palletizing fees

collected from buyers. Some of the ad-

ditional revenues collected by

packer/shippers would likely be passed

back to the growers. If similar to the

1980 experience in shifting to a 25

pound carton, growers would receive an

increase in price roughly equal to the

increase in packing and selling costs.

Growers could see higher returns if

packer/shippers share the increased gas-

sing and palletizing fees collected from

buyers.

References

Jordan, J.L., R.L. Shewfelt, S.E. Prussia

and D.T. Campbell. 1986. “Value in the

Postharvest Handling of Tomatoes: A

Report of the Postharvest Research

Team.” Georgia Agr. Exp. Stat. Res.

Bull. 345.

Smith, Scott A., and Timothy G. Taylor.

2006. “Production Costs and Commod-

ity Budgets for Selected Florida Vegeta-

bles.” Univ. Florida EDIS Doc. FE436.

http://edis.ifas.ufl.edu/FE436

U.S. Dept. Agr. 1965. “Losses in Agri-

culture.” U.S. Dept. Agr. Handbook 291.

VanSickle, John J. and Mario Castejon.

1990. “Economic Implications of a

Change in the Size of Tomato Carton

from 25 to 20 Pounds.” Proc. Fla. State

Hort. Soc. 103: 226-229.