Population Differentiation of Wheat Leaf Rust Fungus Puccinia triticina in South Asia

Leaf or brown rust caused by Puccinia triticina (Pt) is one of the most important diseases of wheat. Among the rusts, it is the most ubiquitous in all the wheatgrowing regions and causes considerable yield loss. Microsatellite marker-based genotyping and virulence- based phenotyping of 48 pathotypes of Pt was performed. The pathotypes exhibit low virulence frequencies for Indian leaf rust differentials Lr24, Lr9, Lr10, Lr19, Lr28 and Lr9. Using avirulence/virulence formula six major clusters of pathotypes were observed, revealing high degree of phenotypic variation. Molecular analysis performed using SSR markers showed high genetic diversity among the pathotypes, and grouped them in seven major clusters. The percentage of polymorphic loci ranged from 17.95 to 84.62, Nei's gene diversity from 0.07 to 0.32 and Shannon's information index from 0.11 to 0.47. Analysis of molecular variance revealed significantly high genetic variation within Pt population. Mantel's Z test proved low positive correlation (r = 0.28) between virulence and molecular diversity, suggesting independent nature of the duo. These findings offer valuable information for framing suitable disease management strategies through appropriate region-specific gene deployment and improve the understanding of the population biology and evolution of Pt in the Indian subcontinent.