Genetic analysis and mapping of adult plant stripe rust resistance loci in CIMMYT wheat ‘Kijil’ under Mexican and Chinese field environments

Stripe rust, caused by Puccinia striiformis f. sp. tritici , can cause severe yield losses in wheat ( Triticum aestivum L.) during epidemics. Breeding resistant wheat varieties remains the most cost-effective approach to manage this disease; and the identification of new resistance loci is essential for maintaining genetic diversity. The CIMMYT-derived wheat line ‘Kijil’ was highly resistant to stripe rust in both Mexican and Chinese environments. A population of 153 F₅ recombinant inbred lines (RILs) was derived from a cross between Kijil and the susceptible parent ‘Apav#1’. The population was phenotyped for stripe rust resistance across seven environments in two countries and genotyped using a genotyping-by-sequencing (GBS) platform. Inclusive composite interval mapping (ICIM) was used to construct a genetic map and identify significant resistance quantitative trait loci (QTLs) using 5,468 polymorphic markers. Mapping revealed the known resistance loci Yr29 , Yr30 and QYr.hzau-3AS , along with two novel loci, QYr.hzau-2BS and QYr.hzau-5DL , across both Chinese and Mexican rust environments. Among these, QYr.hzau-2BS accounted for 11.75% to 19.19% of the phenotypic variance. A corresponding KASP marker, KASP_2BS, was developed to facilitate marker-assisted selection. Based on the mapping interval, two candidate genes underlying this locus were predicted. Further analysis revealed that Yr29 showed significant additive effects with other stripe rust resistance genes/loci, and the combination of Yr29 , Yr30 , and QYr.hzau-2BS reduced disease severity by up to 67.8%. Our findings suggest that Kijil and RILs carrying Yr29 , Yr30, and QYr.hzau-2BS can serve as valuable donors for breeding wheat varieties with improved stripe rust resistance.