characterization of streptomyces scabies in potato
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Potatoes
Characterization of Streptomyces scabies
causing Common Scab of Potatoes
By
Sania Shoukat
Potatoes
CONTENTS
Introduction (Potatoes)
Characterization
Streptomyces scabies
INTRODUCTIO
N
(POTATOES)
“The potato is on the frontline in the fight
against world hunger and poverty.”
(Jacques DioufDirector-General, FAO)
Potato •Papa (Latin Americans), patata (Spaniards),potato...•The potato is a tuber, not a “tubular”
•Scientific Name : Solanum tuberosum•Family :Solanaceae (or nightshade family of flowering plants (Korpan et al.,2004)
•largest genus, with over 1000 species (OECD, 2008)•world's fourth most important food crop
Potatoes
Potatoes as staple food
“ Solanum tuberosum, the “humble tuber”
that spread from its Andean birthplace across six continents, staving off hunger,
fuelling economic developmentand changing the course of world history. ”
world’s number one non-grain food commodityvaluable cash crop for millions of farmers.
Potatoes
POTATOES ARE GOOD FOR YOU
Potatoes
International Year of Potato (IYP) 2008
The IYP mission: raise awareness of the importance of the
potato– and that of agriculture in general –in addressing issues of global concern,
including hunger, poverty and threats to the environment
IYP presented unique opportunity to make a valid and effective contribution
towards meeting the Millennium Development Goals
Potatoes
Potato productionglobal production of 314 million
T. (FAO, 2008).total production of 2542
thousand tonnes (Anonymous, 2008-2009)
Production estimated in 2009-10 to 3.14 million T in Pakistan.
Potatoes
THREATS
Ralstonia solanacearum (brown rot or bacterial wilt)S
Phytophthora
infestans (late
blight);
Erwinia carotovora(black leg
and Erwinia rot)
Clavibacter michiganense (ring rot)
Streptomyces scabies (common scab)
Alternaria solani (early blight)
Pathogenic problems includes
(Kabeil et al., 2008)
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Streptomyces
scabies
(Common scab
of potato)
Potatoes
Common scab of potato
One of the major bacterial pathogensPathogen: Streptomyces scabies
(gram-positive actinomycetes)Order: ActinomycetalesFamily:StreptomycetaceaeGenus :StreptomycesHosts: including radish, beet ,carrot,
potato (Solanum tuberosum) (Goyer and Beaulieu 1997).
Common scab pathogen – Streptomyces scabies
Potatoes
Potatoes
Losses caused by StreptomycesSerious disease of potatoesPrevalent in about 90% of the potato fields
in all potato growing areas of Pakistanaffecting the quality and market valuee95 % incidence in Taxila and Rawalpindi
region(Shazia et al., 2009-2010)
maximum incidence in Gujar Gabral in Swat(Khan etal., 1985)
Potatoes
When should I expect it?
Dry, alkaline, sandy or chalky
soils
Hot dry summers
disease is an like a bacterium, but with threads of mycelium-like fungi. It lives in the soil,
infecting tubers through natural openings such as lenticels
Characterization
Potatoes
Potatoes
Characterization
(Loria et al. 1997).
over 400 identified species of Streptomyces
and only a fraction of these
are pathogenic on potato tubers
(Bouchek-Mechiche et al ., 2000Song et al., 2004.).
streptomycetes have been
classified into a number of species
by various scientific studies
based on 16s ribosomal DNA (rDNA) sequence,
biochemical characteristics
Potatoes
S.scabies were identified by the following biochemical tests
Gram stain (Gregerson, 1978) Melanin production on peptone yeast extract-iron agar
and tyrosine agar medium; starch Hydrolysis ; hydrogene sulfide production Nitrate reduction gelatin liquification Catalase production oxydase reaction urease production 3 and 5% sodium chloride(NaCl) tolerance.
(Schaad et al, 2001) Streptomyces scabies negative response for oxidase,
urease, indole production and nitrate reducatase and positive for production of hydrogene sulfide.
(BENCHEIKH et al., 2007)
Potatoes
Characterization continued………………..
Streptomyces scabies
(synonym, S. scabiei)
best-described species of scab
causing scab it has recently been
divided into several morphologically
similar but genetically distinct
species
(Bouchek-Mechiche, et
al., 2000)
scabies was first described by Thaxter
(1892) re-proposed by Lambert and Loria
(1989) as the predominant
species
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Characterization continued………………..
At present, streptomycetes causing common scab in potato are
classified into
at least 10 different species (Park, et
al., 2003)
at least three additional species cause netted scab in Europe or russet
scab in North America
Another species
causes scab on sweet potatoes
(Clark, et al., 1998)
Potatoes
Potatoes
Characterization continued………………..
A distinct acid-tolerant species, S. acidiscabies, induces symptoms similar to S.
scabies.(Lambert and Loria, 1989)
S. europaeisca
biei
S. stelliscabie
i
cause common scab of potato
(Bouchek-
Mechiche et al., 2000).
S. reticuliscabiei
was identified as a causal pathogen of netted scab in France.
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Differences between„pathogens“ /PASCO; 2004/
Common scab
Netted scab
Occurrence soil-borne soil-borne
Soil temperature
20° C 17° C
Soil moisture low high
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Characteristics of numerous potato scab-inducing not
consistent with description of S.
scabies or S.acidiscabies.
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.
(Doering-Saad et al., 1992) divided potato scab-inducing strains into three phenotypic
groups
Spore chain morphology ranged from
spiral to flexuous to retinaculum-
apertum to rectus
Spore ornamentation ranged from
smooth to warty to spiny
Potatoes
What can I do about common scab?
Once the crop is affected there is no cure for this
disease. The tubers may look unappetising but they are
still edible. Peeling removes the damaged parts. Storage
is not affected.
Can common scab be avoided?
Potatoes
Use plenty of organic
matter such as compost, leaf mould
and manure
Most effective control is use of resistant variety
Avoid sowing infected seed
disease is very widespread in most soils and so is hard to avoid.
Don't compost diseased peelings or old potatoes.
Potatoes
CONCLUSIONAlthough the scab symptoms caused
by other species do not differ from those caused by S. scabies, but the phenotypic characteristics of this organism clearly differ from those of other pathogens.
S. scabies is the predominant species responsible for the disease other than S. acidiscabies and is limiting factor in potato production.
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Potatoes