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SESSION 3: PATHOGENESIS – EPIDEMIOLOGY AND POPULATION
GENETICS
Race Scenario of Fusarium oxysporum f sp. ciceris,
wilt pathogen of chickpea (Cicer arietinum L.)
M. Sharma, A. Nagavardhini, S. Pande
International Crop Research Institute for Semi-Arid tropics (ICRISAT), Patancheru, Hyderabad-502
324, Andhra Pradesh, India.
E-mail: mamta.sharma@cgiar.org
Fusarium wilt caused by Fusarium oxysporum f.sp. ciceris (Foc) is most wide
spread and predominant disease in all chickpea growing areas worldwide.
Although the FW resistant sources are available, but due to the variability in
pathogen, the efficiency of resistant cultivars is limited. To understand the
variability/ race scenario in Foc in India, out of total repository of 274 isolates of
Foc build from the period of 1995 - 2010, 110 isolates were selected for cultural,
morphological, virulence and genomic diversity representing various chickpea
agro-climatic zones in India. The isolates showed variation in colony colour, type
of mycelium and growth pattern. Wide variation in conidial morphology
(microconidia and macroconidia) and chlamydospore formation with respect to
shape, size and proportion was observed. Significant pathogenic diversity was
found among the 98 isolates based on their virulence reaction on 10 standard
differentials of chickpea. Clustering of isolates based on percentage disease
incidence at 85% similarity resulted in 14 major pathogenic groups. In addition to
4 races reported earlier from India, occurrence of new pathogenic races and
existence of multiple races at one place was observed. Race 6 reaction reported
from California and Mediterranean basin was found in some locations in central,
north east and north west zones of India. Diversity Arrays Technology (DArT) was
used for the first time to understand the diversity in Foc isolates. Restriction
enzyme combination PstI/HpaII was selected to construct the Foc DArT array.
Genotyping of 110 isolates was done by labelling the genomic representations
with the fluorescent nucleotides cy3-dUTP and cy5-dUTP. Out of 1813
polymorphic markers, 1141 exhibited 90% call rate. The Dendroscope analysis
and principle coordinate analysis of 1813 polymorphic markers grouped 110 Foc
isolates in to 4 major groups with subgroups in each group. Each group has
isolates from different regions. The study indicates changed scenario of races in
Indian population of the pathogen and existence of multiple races with in region.
The information generated is of significant importance in resistance breeding
program in chickpea.
Keywords: chickpea, DArT, Fusarium wilt, races
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