Stripe rust, caused by Puccinia striiformis f. sp. tritici, is a serious disease in bread wheat (Triticum aestivum L.).  Identification and use of adult plant resistance (APR) resources are important for stripe rust resistance breeding.  Bread wheat line C33 is an exotic germplasm that has shown stable APR to stripe rust for more than 10 years in Sichuan Province of China.  Here, 183 recombinant inbred lines (RILs) derived from the cross between C33 and a susceptible line X440 were genotyped with diversity arrays technology (DArT) markers to identify resistance quantitative trait locus (QTL).  Field trials were conducted in five years at Chengdu and Xindu of Sichuan Province, using maximum disease severity (MDS) as stripe rust reaction phenotypes.  A total of four quantitative trait loci (QTLs) were detected, respectively designed as QYr.saas-3AS, QYr.saas-5AL, QYr.saas-5BL, and QYr.saas-7DS, explaining 4.14–15.21% of the phenotypic variances.  QYr.saas-5BL and QYr.saas-7DS were contributed by C33.  However, the level for stripe rust resistance contributed by them was not strong as C33, suggesting the presence of other unidentified QTLs in C33.  QYr.saas-7DS corresponded to Yr18 and QYr.saas-5BL remains to be formally named.  The RIL lines carrying combinations QYr.saas-5AL, QYr.saas-5BL, and QYr.saas-7DS showed comparability resistance with C33.  The present study provides resources to pyramid diverse genes into locally adapted elite germplasm to improve the stripe rust resistance of bread wheat.

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a devastating disease that can cause severe yield losses.  Identification and utilization of stripe rust resistance genes are essential for effective breeding against the disease.  Wild emmer accession TZ-2, originally collected from Mount Hermon, Israel, confers near-immunity resistance against several prevailing Pst races in China.  A set of 200 F_6:7 recombinant inbred lines (RILs) derived from a cross between susceptible durum wheat cultivar Langdon and TZ-2 was used for stripe rust evaluation.  Genetic analysis indicated that the stripe rust resistance of TZ-2 to Pst race CYR34 was controlled by a single dominant gene, temporarily designated YrTZ2.  Through bulked segregant analysis (BSA) with SSR markers, YrTZ2 was located on chromosome arm 1BS flanked by Xwmc230 and Xgwm413 with genetic distance of 0.8 cM (distal) and 0.3 cM (proximal), respectively.  By applying wheat 90K iSelect SNP genotyping assay, 11 polymorphic loci (consisting of 250 SNP markers) closely linked to YrTZ2 were identified.  YrTZ2 was further delimited into a 0.8-cM genetic interval between SNP marker IWB19368 and SSR marker Xgwm413, and co-segregated with SNP marker IWB28744 (co-segregated with 28 SNP).  Comparative genomics analyses revealed high level of collinearity between the YrTZ2 genomic region and the orthologous region of Aegilops tauschii 1DS.  The genomic region between loci IWB19368 and IWB31649 harboring YrTZ2 is orthologous to a 24.5-Mb genomic region between AT1D0112 and AT1D0150, spanning 15 contigs on chromosome 1DS.  The genetic and comparative maps of YrTZ2 provide a framework for map-based cloning and marker-assisted selection of YrTZ2.