Assessment and comparison of AFLP and SSR based molecular genetic diversity in Indian isolates of Ascochyta rabiei, a causal agent of Ascochyta blight in chickpea (Cicer arietinum L.)

Ascochyta blight (AB), caused by Ascochyta rabiei (Pass.) Labr. (anamorph), is the most damaging disease of chickpea (Cicer arietinum L.) and is a serious biotic stress constraint for chickpea production. To understand the molecular diversity in A. rabiei populations of India, a total of 64 isolates collected from AB-infected chickpea plants from different agroclimatic regions in the North Western Plain Zone (NWPZ) of India were analyzed with 11 AFLP (amplified fragment length polymorphism) and 20 SSR (simple sequence repeat) markers. A total of 9 polymorphic AFLP primer pairs provided a total of 317 fragments, of which 130 were polymorphic and showed an average PIC value 0.28. Of the SSR markers, 12 showed polymorphism and provided a total of 29 alleles with an average PIC value 0.35. To the best of our knowledge, this is the first report on a comparison of AFLP and SSR diversity estimates in A. rabiei populations. The dendrogram developed based on AFLP and SSR data separately, as well as on the combined marker dataset, grouped the majority of AB isolates as per geographic regions. Model based population structure analysis revealed four distinct populations with varying levels of ancestral admixtures among 64 isolates studied. Interestingly, several AFLP primer combinations and SSR markers showed the locus/allele specific to AB isolates of certain regions, e.g., Hisar, Sriganganagar, Gurdaspur, and Sundarnagar. Genetic variability present in AB isolates of the NWPZ of India suggests the continuous monitoring of changes in A. rabiei population to anticipate the breakdown of AB resistance in chickpea cultivars grown in India.