sudden death syndrome of soybean dr. jason bond, plant pathologist southern illinois university...
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Sudden Death Syndrome of Soybean
Dr. Jason Bond, Plant PathologistSouthern Illinois University
Sudden Death Syndrome• Disease and Impact• Pathogen Biology• Cultural Management• Host Resistance
Yield Losses – Northern US
Disease3-year average (bu in millions)
Soybean cyst nematode 122.4
Phytophthora rot 42.1
Seedling diseases 41.1
Sudden death syndrome 22.7
Charcoal rot 17.6
Brown spot 16.2
Brown stem rot 14.1
Anthracnose 11.3
Sclerotinia stem rot 10.0
Frogeye leaf spot 7.6
Fusarium root rot 7.6
Source: Allan Wrather, UM, Portageville, MO
Fusarium virguliforme (= F. solani f. sp. glycines)
• Soilborne, root rotting fungus that colonizes tap root and crown
• Produces a toxin(s)• Foliar symptoms generally start at R2 in field
Symptoms
Similar Foliar Symptoms
Stem Canker
Phytophthora stem rot
Similar Foliar Symptoms
Brown Stem Rot
SDS
Spread of SDS
1971
1984
1984
1984
1984
1986
1986
1992
1986
1986
1993
19972002
2004
1993
2000
1999
2000
1997 1997
1997
1997
2005?
Rating Foliar Symptoms
• Disease Incidence (DI) - % of plants in the plot showing leaf symptoms.
• Disease Severity (DS) - Severity of diseased plants scored on a 1-9 scale.
• Disease Index (DX) = (DI*DS)/9
DX 25 - 30
DX 50 - 60
DX 60 - 75
Impact on Yield• SDS is correlated to the yield potential provided by the
environment• Popular misconception that SDS does not cause yield loss
Yield loss occurs when infection occurs early in a high yielding environment (adequate rainfall), and symptoms are expressed at or near flowering.
Impact on Yield
Environment
SDS severity is increased with:
Early planted fields
Compacted soil
High moisture, low soil temperature during vegetative growth
Cool period during flowering
Presence of soybean cyst nematode
Crop rotations – inconsistent
Impact of Planting Date
Aug 18 Aug 25 Sep 1 Sep 100
5
10
15
20
25
30
35
40
45
50
May 10June 2June 27
Planting Date
Dis
ease
Inde
x (D
X)
Date Rated
Impact of Planting Date 2009 – SDS Variety Trials
Valmeyer, IL planted 4/24 Havana, IL planted 4/26
Both fields have a history of SDS.
Carbondale, IL planted 5/20 Paris, IL planted 5/29
Both fields have a history of SDS, Carbondale was also infested with the pathogen.
Impact of Planting Date 2009 – SDS Variety Trials
Chemical Control• Current fungicides do not limit SDS in the
field– Some fungicides impact severity in
greenhouse trials– Herbicides can reduce symptom severity in
the field• Lactofen (X.B. Yang, Iowa State U.)• Experimental products• Generally, short lived reduction
– Induced resistance, affecting toxin movement or expression, ?
Chemical Control• Could a product provide short-term
protection to mirror that observed with delayed planting?
- 2010 Seed Care trials with
Scott Cully, Syngenta R&D
- Havana and Valmeyer
- Fungicide/Nematicide trts.
Compacted Soils
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0
m e t e r
D I S E A S E I N D E X ( M Y E R S , 1 9 9 7 ) , D X .
0
2 0
4 0
6 0
8 0
1 0 0
1 2 0
0
1 5
3 0
4 5
6 0
7 5
0 2 0 4 0 6 0 8 0 1 0 0 1 2 0
m e t e r
S O I L M A C R O P O R O S I T Y , %
0
2 0
4 0
6 0
8 0
1 0 0
1 2 0
m e
t e
r
6
1 0
1 4
1 8
2 2
2 6
3 0
3 4
Vick et al. 2005. Canadian J. of Plant Path. 28:77-83.Vick et al. 2003. Plant Dis. 87:629-632.
Pathogen Research
•Identification of fungal genes involved in the development of SDS
•Karyotyping (Chromosomal organization)
• SDS-SCN interaction
A. Fakhoury, Southern Illinois U.
Pathogen Research
• Generate REMI mutants– ~800 mutants have been generated so far
– Mutants screened for conidiation and growth pattern
• Generate and collaborate to generate sequence material– Necessary in identifying targets for disruption
– Expedite gene disruption
– Permits genomic and comparative genomic studies (complements karyotyping, population studies…)
Tools Developed• Optimize transformation system
• Optimize site directed mutagenesis
• Optimize transformation system
– A split-maker approach is being tested to disrupt genes
– Several genes are being targeted at this point
– Snf1, grx, fsr1 and several kinases
A GFP expressing strain of the pathogen was produced
Objectives
• Identification of fungal genes involved in the development of SDS
• Identification and characterization of pathways involved in virulence and pathogenesis
• Detection of the karyotypic variation among F. virguliforme isolates
Karyotypic Variation Among Isolates
GTBM
• F. virguliforme has 11 chromosomes
• We estimate the size of the genome at ~ 33 Mbp
• Tested isolates exhibited polymorphism (differences) in terms of the sizes of their chromosomes
• This polymorphism may be linked to the varying levels of aggressiveness exhibited by different isolates of the pathogen
SDS interactions with SCN
• Synergistic – – Roy et al., 1989- greenhouse– McLean and Lawrence, 1993 - greenhouse– Rupe et al., 1991, field trials– Hershman et al., 1990, field trials– Xing and Westphal, 2006, microplots
• Additive – Gao et al., 2006 - greenhouse
Distribution of SCN
Source: G. Tylka, ISU
SDS and SCN
SDS and SCN
SCN juvenile and mycelium of F. virguliforme
Could Other Nematodes Be Involved?
SDS
Root knot nematode M. incognita
Greenhouse trial Soybean cultivars were selected that differed for
resistance to SCN, RKN, or SDS
Each cultivar was challenged with the GFP-expressing virulent Fv transformant, the GFP-expressing avirulent Fv transformant, or several nematode/fungus co-inoculations
The experiment consisted of 36 treatments replicated 5 times
97-1610 Spencer GH3983 Forrest P94M500
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Foliar scorch P6B5
P6B5+SCN
P6B5+RKN
Cultivar
Rat
ing
Virulent Fv
Virulent Fv + SCN
Virulent Fv + RKN
Cultivar H. glycines M. incognita F. virguliforme
Forrest R R R
P94M50 R S S
Spencer S S S
GH3983 S S R
LS97-1610 S R R
97-1610 Spencer GH3983 Forrest P94M500
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Foliar scorchP23C5
P23C5+SCN
Cultivar
Rat
ing
Cultivar H. glycines M. incognita F. virguliforme
Forrest R R R
P94M50 R S S
Spencer S S S
GH3983 S S R
LS97-1610 S R R
Avirulent Fv
Avirulent Fv + SCN
97-1610 Spencer GH3983 Forrest P94M500
5
10
15
20
25
30
Root colonization (QPCR)
P23C5
P23C5+SCN
Cultivar
ng
fu
ng
al D
NA
/ug
to
tal
DN
A
Cultivar H. glycines M. incognita F. virguliforme
Forrest R R R
P94M50 R S S
Spencer S S S
GH3983 S S R
LS97-1610 S R R
Avirulent Fv
Avirulent Fv + SCN
Host Resistance
• Quantitative resistance• Controlled by multiple genes• Difficult to test in the field
Host Resistance
• Mapped genes from PI 567374 in greenhouse.– Genes on linkage group D2 and I.
• Mapped genes from Ripley in field with SSR markers using field data.
– Genes on linkage group D2 and L.
• Genes have been confirmed and are conducting marker-assisted backcrossing
B. Diers and M. Schmidt B. Diers
B. Diers
Evaluating Resistance to SDS• Illinois Soybean Association
– SDS Commercial Variety Trial
– USDA Uniform and Regional Trials
• North Central Soybean Research Program
−NC Regional Trial
Success equals ?
A successful trial has a mean DX of at least 15 – 20 in susceptible check varieties.
Factors That Insure Success
• Field with history of SDS and/or inoculation when needed
• Early planting
• Irrigation
• Disease evaluation at R6
• Appropriate check varieties
for the maturity group
• A good rating scale
SDS Variety TrialsOver 1,800 varieties (includes
Public Lines) MG 1-5
Six locations overall3-4 for each MGOver 16,000 plots
Results distributed via Email, Websites, Mail, Popular press, Companies
www.soybeandiseases.infowww.vipsoybeans.orgwww.soybean.siu.edu
Variety Performance in 2009
Relative DX
Rating Percentage of EntriesMG 1 - 3.4
Percentage of EntriesMG 3.5 - 5.0
0-20 Res. 6 5
21-40 Mod. Res. 17 17
41-60 Mod. Susc.
23 32
61+ Susc. 54 46
Greenhouse Assays
• Benefits/Limitations• More art than science• Agreement with known field reactions
– Hashmi obtained correlation of .80– Collaborative university trials – Several blind
trial competitions yielded correlations 0 - .59
Hashmi et al. 2005. Plant Health Progress doi:10.1094/PHP-2005-0906-01-RS.
Waterbath Method
Tray Method
Pictures – R. Bowen, UIUC
1 –Typical plant, showing no symptoms.
3 – Leaf with obvious, inter-veinal chlorosis
Pictures – R. Bowen, Univ. of Illinois
Pictures – R. Bowen, UIUC
Wish List
• Resistant commercial varieties and public germplasm
• Chemical treatments – seed, foliar, in-furrow
• Factors that contribute to severe disease
• Increased resolution and consistency in field trials
• More efficient greenhouse/laboratory screening assays
Summary
