Genetic analysis and molecular mapping of stripe rust resistance in an excellent wheat line Sanshumai1

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici (Pst), is one of the most widespread diseases in wheat (Triticum aestivum L.). Planting resistant cultivars has been constantly practiced for decades as the best strategy to defense against the variations of prevalent Pst races. The wheat line Sanshumai1 was developed from an interspecific hybridization of Haynaldia villosa (L) Schur. (2n=2x=14, VV)/Triticum turgidum L. var. durum (4n=4x=28, AABB)///Yanxiaomai. Sanshumai1 has all-stage resistance to most of known stripe rust races in China, including three widely virulent races CYR31, CYR32, and CYR33. To identify stripe rust resistance gene in this line, Sanshumai1 was crossed with the susceptible genotype, Mingxian169, and the F-1, F-2, F-3, and BC1 generations were inoculated with Pst races under the controlled greenhouse conditions. The genetic results indicated that two stripe rust resistance genes in Sanshumai1, temporarily designated as YrS1 and YrS2, confer resistance to CYR31 and Su11-11, respectively. Using bulked segregant analysis (BSA) methodology, we identified five simple sequence repeat (SSR) markers and two expressed sequence tag-sequence tagged site (EST-STS) markers associated with YrS1 on the short arm of chromosome 3D. The genetic distances of the two closest flanking markers, namely Xcfd79 and Xwmc674, were 4.1 and 8.7 centiMorgans, respectively. In addition, we identified four SSR markers associated with YrS2 on the long arm of chromosome 4D. The genetic distances of the two closest flanking markers, namely Xcfd84 and Xgwm194, were 6.8 and 7.1 centiMorgans, respectively. Based on the chromosomal location, reaction patterns, and pedigree analysis, these two genes are likely novel resistance genes. These two genes and the flanking markers developed from this study are expected to be useful in pyramiding YrS1 and YrS2 with other Yr genes to develop wheat cultivars with high-level and durable resistance to stripe rust and may also benefit marker assisted selection (MAS) in breeding programs.