Comparative virulence and molecular diversity of stripe rust (Puccinia striiformis f. sp. tritici) collections from Pakistan and United States.

Abstract

Information on virulence and molecular diversity of Puccinia striiformis f. sp. tritici (Pst) is a pre-requisite for mitigating the substantial yield losses caused by the stripe rust pathogen in Pakistan, the United States and other countries of the world. This study was undertaken to analyze both virulence and molecular diversity of 46 Pst isolates from Pakistan, in comparison with 9 US isolates. Avirulence to stripe rust resistance genes Yr5, Yr15 and YrSP was common among all tested isolates. Isolates from Pakistan had low virulence frequency for differentials carrying Yr2, (Yr10, YrMor) and (Yr2, Yr4a, YrYam). Clustering based on virulence data grouped contemporary isolates together and revealed high genetic diversity among pathotypes of both countries. Molecular analysis using sequence tagged site (STS) and microsatellites markers revealed high diversity based on polymorphic information contents (PIC)and marker index (MI) which was higher for SSRs (0.78 & 39.51, respectively) than STS markers(0.04 & 0.29, respectively). Dendrogram based on molecular marker data grouped together contemporary pathotypes indicating genetic similarity. Pathotypes belonging to both countries clustered together indicating common ancestry. Furthermore, very low correlation (r=0.08) was observed between virulence and molecular diversity showing independence in both trends of diversity. The depicted virulence pattern of Pst isolates will guide in devising cultivar improvement efforts for stripe rust resistance. © 2012 Friends Science Publishers