Mapping of gene conferring adult-plant resistance to stripe rust in Chinese wheat landrace Baidatou

Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive foliar disease of wheat worldwide. Sustainable control of the disease is preferably achieved by deploying stripe rust resistance genes in wheat cultivars. Our previous studies have shown that Baidatou, a Chinese wheat landrace, displayed good adult-plant resistance (APR) to wheat stripe rust in Gansu Province, an epidemic region for stripe rust in China. To elucidate the genetic basis of APR to stripe rust in Baidatou, a cross between Baidatou and Mingxian 169, which is susceptible to all the known Chinese (Pst) races, was performed. Adult plants of F-1, F-2 and F-2:3 generations derived from the cross Mingxian 169/Baidatou were inoculated in the field with the most prevalent Chinese Pst race, CYR33, in Yangling, Shaanxi Province, during 2009-2010 and 2010-2011 crop seasons, respectively. The results showed that the resistance of Baidatou to stripe rust was conferred by a single dominant gene. Six hundred and sixty simple sequence repeat (SSR) markers and 128 sequence-related amplified polymorphism (SRAP) markers were screened for association with the resistance gene to stripe rust using bulked segregant analysis. Four polymorphic SSR markers and two SRAP markers were identified to be linked to the resistance gene. A linkage map was constructed with six molecular markers and the resistance gene. The genetic distance of two flanking SSR markers to the resistance gene, temporarily designated YrBai, was 3.6 and 5.4 cM, respectively. Based on the position of the SSR markers on the wheat chromosome, YrBai was located on chromosome 6DS. According to the rust reaction patterns, SSR marker allele analysis and the pedigree of the Yr genes on chromosome 6D, YrBai is likely to be a novel APR gene against stripe rust. The specificity of the two flanking markers of YrBai was validated in 99 wheat germplasms. The gene and its flanking markers should be useful for developing wheat cultivars with durable resistance.