Population distribution and differentiation of Puccinia graminis tritici detected in the Indian subcontinent during 2009–2015

Abstract

Surveys on wheat stem rust were conducted in major wheat-growing areas of the Indian subcontinent during 2009–2015 to determine the virulence phenotypes and simple sequence repeat (SSR) genotype diversity of Puccinia graminis Pers. f. sp. tritici Eriks. E. Henn (Pgt). Rust-infected stems or leaves of wheat were collected and inoculated on a susceptible wheat cultivar. Indian stem rust differential lines were used to designate Pgt pathotypes in these samples. About 80% of the samples analyzed during the study were from central and southern India. Twelve pathotypes of P. graminis f. sp. tritici were designated in 574 samples analyzed during the study. The severity and incidence of stem rust were maximum during 2013–2014 followed by 2012–2013. Pathotypes 40A and 11 designated in 36.8% and 32.6% of the samples, respectively, were the most predominant. The stem rust resistance genes Sr7a, Sr26, Sr27, Sr31, Sr32, Sr33, Sr39, Sr40, Sr43, SrTmp, and SrTt3 were found to confer resistance to all the pathotypes identified duing the study period. These genes in combination with other slow rusting genes could be used in stem rust resistance breeding programme for the Indian subcontinent. The analysis of SSR marker-based, genotypic and virulence-based phenotypic data revealed a high degree of variability in the Pgt population. The information generated here promises to be a useful guide for orienting rust resistance breeding programme and gene deployment for guarding South Asian wheat from the stem rust menace.