Virulence and genetic diversity of Puccinia striiformis f. sp. tritici isolates in sub-mountainous area of Punjab, India

Abstract

Information on the pathogen virulence profile and diversity across locations is crucial for host germplasm improvement and deployment. The rapid acquisition of virulence to host resistance by the wheat yellow/stripe rust pathogen (Puccinia striiformis f.sp. tritici: Pst), makes it crucial to know about its virulence and pathotype diversity. To assess the status of virulence and pathotype diversity in the sub-mountainous areas of Punjab, 27 stripe rust infected wheat samples from initial foci developed early in crop season were collected, multiplied and pathotyped using differential sets carrying known resistance genes. All the Pst isolates were virulent on lines carrying genes Yr2, Yr3, Yr4, Yr6, Yr7, Yr8, Yr9 and were avirulent on genes Yr1, Yr5, Yr10, Yr15 and Yr24/Yr26. Out of 27 isolates, only 4 pathotypes were detected indicating low pathotype diversity in Punjab. Two pathotypes i.e. 46S119 and 110S119 were most prevalent in Punjab. Other pathotypes recorded were; 238S119 and 110S84 but their prevalence was less. Three Pst pathotypes (46S119, 110S119 and 238S119) were tested for aggressiveness and it is found that 238S119 was more aggressive followed by 110S119 as spore production and uredial density was higher for this pathotype. Genetic diversity of the isolates was studied by using 74 SSR markers developed by different researchers. Scatter plot generated from the molecular data revealed the high genetic diversity among the isolates of Punjab. None of the pathotype showed any location specificity. Low pathotype diversity observed can be due to the cultivation of cultivars carrying only 1 or 2 major genes and high genetic diversity arised due to local adaptation, evolution for increased aggressiveness, mutation or parasexuality.