Characterization of stem rust resistance gene <i>Sr2</i> in Indian wheat varieties using polymerase chain reaction (PCR) based molecular markers

Abstract

Stem rust or black rust is one of the most important diseases of wheat worldwide. In India, central, peninsular and southern hill zones are particularly prone to stem rust where favourable environmental conditions exist. The recent emergence of wheat stem rust race Ug99 (TTKSK) and related strains threatens global wheat production as Ug99 overcome resistance gene Sr31 effective for many years. Resistance gene Sr2, derived from cultivar ‘Hope’ is responsible for slow rusting and providing partial but durable resistance against stem rust of wheat. In addition to other unknown minor genes (Sr2 complex), this gene tends to be non-specific and is currently effective against all isolates of Puccinia graminis tritici throughout wheat-growing regions of the world. A set of 135 bread wheat varieties developed in the last forty years for prominent northern, central, peninsular and southern hill regions of India was screened with molecular markers, CsSr2 and GWM533, developed and identified for Sr2 gene. Out of 135 varieties screened, 92 confirmed the presence of Sr2 gene at molecular level. The molecular information of Sr2 gene was corroborated with the available morphological marker data for selected varieties to evaluate the efficacy of these molecular markers in Indian wheat germplasm. It was observed that these two molecular markers in combination provide accuracy in 92% lines for this gene at molecular level with presumed Sr2 status in Indian wheat varieties. It is proposed that the use of CsSr2 and GWM533 will help in gene pyramiding of Sr2 along with other stem rust resistance genes in future wheat varieties to accelerate Indian breeding program for rust resistance.

Keywords: Wheat, stem rust, Puccinia graminis f.sp. tritici (Pgt), Sr2 gene, molecular marker

African Journal of Biotechnology Vol. 12(18), pp. 2353-2359