LAUSR

In India, systematic wheat yellow rust survey and pathotype (race) analysis work began in 1930. However, the information on population structure and genetic diversity of yellow rust pathogen is not available. We conducted studies on population structure and genetic diversity of Puccinia striiformis f. sp. tritici (Pst) pathotypes using 38 simple sequence repeat (38 SSR) primer-pairs. Bayesian assignment and discriminant analysis of principal components (DAPC) indicated the presence of two distinct Pst sub-populations (Pop1 and Pop2) along with 37.9% admixed pathotypes. The unweighted pair-group method with arithmetic mean (UPGMA) also categorized these pathotypes into two major clusters. Principal coordinates analysis (PCoA) explained 20.06% and 12.50% variance in horizontal and vertical coordinates, respectively. Index of association (IA) and the standardized index of association (̅d) showed that Pst sub-populations reproduced asexually (clonally). In total, 102 alleles were detected, the expected heterozygosity (Hexp) per locus ranged from 0.13 to 0.73, with a mean of 0.47. The average polymorphic information content (PIC) value of 0.40 indicated high genetic diversity among pathotypes. Analysis of molecular variance (AMOVA) revealed 12% of the total variance between sub-populations, 11% among the pathotypes of each sub-population, and 77% within pathotypes. A significant moderate level of genetic differentiation (Fst = 0.122, p < 0.001) and gene flow (Nm = 1.80) were observed between sub-populations. The Pst virulence phenotypes showed a weak positive correlation (R2 = 0.027, p < 0.02) with molecular genotypes.