Genetic Differentiation among Populations of Venturia inaequalis in Kashmir: A North-Western State of India
Apple scab, caused by Venturia inaequalis, is one of the most damaging diseases worldwide on apple and is currently managed mainly by scheduled applications of fungicides. The aim of the present study was to understand the pathogen population structure in Jammu and Kashmir which is important for breeding and deployment of resistant cultivars. Twenty-seven isolates of V. inaequalis were sampled from commercial apple growing areas to estimate differences in pathogen populations using Random Amplified Polymorphic DNA (RAPD) 10 -and 20-mer primers. RAPD data analysis grouped 27 isolates in to three major clusters accommodating 10, 10 and 7 isolates each. The categories did not follow any geographic or source cultivar pattern. Allele frequencies among the three populations varied from 0.00 to 1.00. The average genetic diversity within each population (HS) over all loci studied was 0.21, 0.23 and 0.20 in Ganderbal, Pulwama and Srinagar, respectively thereby showing high genetic diversity within each population. The average genetic differentiation at a single locus among all sampled populations (GST) was 0.12. The overall gene flow (Nm) was 3.54 while the gene flow values at a single locus ranged from 0.70 to 69.32. Pair-wise genetic differentiation values (FST) among all loci were low, thereby indicating high diversity among the three populations. Analysis of molecular variance (AMOVA) obtained after clustering the isolates at district level showed highly significant genetic differentiation among populations with 5.46 and 94.54% genetic variability recorded among and within district populations, respectively. Population genetic analysis of V. inaequalis is the first molecular analysis of this pathogen from the India and especially from Jammu and Kashmir, a north-western Himalayan state of India.
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