QTL Analysis Of Stripe Rust Resistance In Wheat Varieties And P9897 Molecular Marker-assisted Breeding

Wheat stripe rust,caused by Puccinia striiformis f.sp.tritici?Pst?,is one of the most devastating diseases in wheat.Due to the large-scale widespread planting pattern of single-gene resistant varieties,the directional selection pressure of the pathogen is very strong,which is likely to cause mutation of pathogen.Therefore,there is an urgent need to finding and mapping new resistance genes and develop more resistant varieties to prevent and control the stripe rust epidemic and ensure wheat production safety.In this study,we screened candidate genes of resistance through molecular mapping of disease resistance genes in wheat variety Toni.And two resistant QTLs of P9897 were successfully introgressed into three Chinese elite varieties.Achieved the following results:1.Toni,Mingxian 169,and Avocet S were assessed stripe rust responses in the greenhouse using CYR29,CYR30,CYR32,CYR33,and CYR34 five races.At the seedling stage,three varieties showed high susceptibility to five test races.At the adult-plant stage,Mingxian 169and Avocet S still showed high susceptibility,while Toni showed resistance.The disease resistance assessing results of the three varieties in the field were the same as those in the greenhouse,indicating that Toni has typical adult-plant resistance.2.Through field experiments,the frequency distributions of mean infection type and disease severity values of the F₇ RIL population of Mingxian169/Toni were continuous,indicating quantitative inheritance of APR to stripe rust.ANOVA confrmed signifcant variation?P<0.05?in DS and IT among RILs,environments and line×environment interactions.Broad-sense heritability was estimated at 0.90 for the IT data and 0.88 for the DS data across three locations,indicating that the APR was highly heritable and should be easily transferred into breeding materials.3.Genotyping and QTL mapping of 171 F₇ populations were performed by using 35K SNP gene chip.Two QTLs resistant to stripe rust were found in wheat chromosomes 3AS and3BS,which were designated QYrto.swust-3AS and QYrto.swust-3BS.QYrto.swust-3AS,located in a 2.25-cM interval spanned by SNP markers AX-95240191 and AX-94828890,explained 32.5-48.2%and 21.9-56.3%of the phenotypic variation in DS and IT for across all environments,respectively.QYrto.swust-3BS was mapped to a 0.91-cM interval fanked by SNP markers AX-94509749 and AX-94998050.The corresponding phenotypic variances explained on the basis of DS and IT were 31.6-46.3%and 22.7-55.0%across environments,respectively.4 SNP sequences were used to search IWGSC RefSeq v 1.0 to determine their physical positions using BLAST.Based on the locations of the markers,QTL QYrto.swust-3AS was located within a 7,920,927-10,144,518 bp physical region on chromosome 3A.Sixty fve HC?high confdence?and 46 LC?low confdence?genes were annotated in this region?IWGSC RefSeq Annotations V1.0?.Among the HC genes,11?16.9%?contained an NB-ARC domain and 9?13.8%?contained protein kinase domains either of which could contribute to disease resistance.QYrto.swust-3BS was located within a 1,613,170-6,379,378 bp physical region fanked by SNP AX-94745543 and AX-94998050.One hundred and thirty three HC and 136 LC genes were annotated in this region.Among the HC genes,there were 14?10.5%?protein kinase domain genes any of which might contribute to disease resistance.5.P9897 was crossed with Chuanmai 42,Xiangmai 25,and Zhengmai 9023,respectively,with P9897 as the male parent and the three elite varieties as the female parents.The F₁seeds were obtained and planted in the field.We performed a bulk harvest before the F₅generation for each cross,then we screened F₅ generation plants.A total of 114 F₆ lines were selected due to their resistance to stripe rust,moderate plant height,and high tiller and spikelet numbers.6.In the 114 F₆ lines of the three cross combinations,we utilized the MAS method to select27 lines which combined two QTLs from P9897.We also verified that molecular markers Xcfd73 and Xgwm120,which are closely linked to QYr.nafu-2BL,and Xbarc87 and Xbarc133,which are closely linked to QYr.nafu-3BS.7.Through the evaluation of agronomic traits and resistance assessing of these 114 F₆families,data on yield-related agronomic traits such as plant height,spikelet number,tiller number,and 1000-grain weight,as well as infection type?IT?and disease severity?DS?.Combined with the results of QTL detection,we successfully selected 13 lines that successfully pyramiding two target QTLs and had excellent agronomic traits and disease resistance.