Identification And Validation Of A Major QTL For All-stage Stripe Rust Resistance In The Winter Wheat Line 20828

Stripe rust is one of the most serious diseases of wheat.Identification and utilization of new resistance genes are essential for breeding resistant cultivars.Wheat line 20828 has exhibited high levels of stripe rust resistance for over a decade.However,the genetics of stripe rust resistance in this line has not been studied.A recombinant inbred line(RIL)population(2CN)was developed from a cross between 20828 and Chuannong 16.The RIL population was genotyped with the Wheat55 K SNP(single nucleotide polymorphism)array and SSR(simple sequence repeat)markers and evaluated in four environments with current predominant Puccinia striiformis f.sp.tritici races including CYR32,CYR33 and CYR34.The results of this study include: 1.The high-density genetic linkage map of the 2CN population was constructed.The genetic map contains 34 linkage groups with a total length of 3005.04 cM and the average interval between adjacent markers is 0.84 cM.2.The disease index(DI)of the 2CN population lines and the parent were evaluated among different environments.The DI of 20828 ranged from 11.11 to 11.74,that of CN16 ranged from 59.26 to 88.89,and that of the 2CN population ranged from 11.74 to 96.68.20828 had significantly lower DI than CN16 in each environment.The frequency distribution for DI was indicative of multigenic inheritance.The H2 of DI was 0.999.3.Four stable QTLs for resistance to stripe rust were identified and located on chromosome 1B(2 QTLs),4A and 6A respectively.Among them QYr.sicau-1B.1 was a major locus,and explained 16.32 to 39.45% of the phenotypic variance.As expected,the resistance allele of QYr.sicau-1B.1 was derived from 20828.This QTL was located in a 1.76 cM interval between SSR markers Xwmc156 and Xwmc216.QYr.sicau-6A explained 1.95 to 4.05% of the phenotypic variance.The resistance allele of this QTL was also derived from 20828.Resistance alleles for QYr.sicau-1B.3 and QYr.sicau-4A were derived from 20828 and CN16,respectively.The phenotypic variance explained by these loci ranged from 5.39 to 18.21% and 1.10 to 4.87%,respectively.Three minor stable QTL also added to the resistance level of QYr.sicau-1B.1.Compared with previous studies on stripe rust resistance genes based on the Chinese spring reference genome sequence,QYr.sicau-1B.1 is a new QTL resistant to stripe rust.4.QYr.sicau-1B.1 was further verified by analysis of the closely linked SSR markers Xwmc216 and Xwmc156 in four other populations with different genetic backgrounds.The results showed that QYr.sicau-1B.1 reduced the stripe rust DI by up to 82.8%.5.By analyzing the flanking marker sequences of QYr.sicau-1B.1 and the genes in the interval,we found that there are 162 and 136 genes in the corresponding physical interval of Chinese spring and wild emmer,respectively,among which 8 genes related to disease resistance have been reported by predecessors.Our results provide valuable information for further fine mapping and cloning as well as molecular-assisted breeding with QYr.sicau-1B.1.