Screening Of Varieties And Mapping Of Loci For Bacterial Blight Resistance In Rice Germplasm Resources

Rice bacterial blight disease,caused by Xanthomonas oryzae pv.oryzae(Xoo),is one of the most devastating rice diseases worldwide.In this study,total 701 of rice germplasm from 32 countries and 25 provinces of China were evaluated resistance to BB by inoculation with four representative Xoo strains of China and the Philippines.Genome-wide association analysis(GWAS)was performed based on the phenotypic data of lesion lengths and the SNP genopypes of rice germplasm.The major results are as follows:1.701 rice germplasm were inoculated with Xoo strains Zhe173(C3),GD1358(C5),PXO61(P1)and PXO339(P9a)to identify rice varieties for bacterial blight resistance.29 rice germplasm resistant to four Xoo strains were found.Among them,Little Red Valley and Hao Ge Lao,were resistant to strongly virulent strain C5 from Guangdong.2.A total of 219 loci containing 5432 significantly associated SNPs were identified by GWAS based on the lesion lengths and SNP genoptypes of 701 rice germplasm.Among them,two regions(R34and R35)were located known fine-mapped four R genes(Xa32,Xa35,Xa36 and Xa40)and one cloned R gene Xa4,another two regions(R36 and R40)were located close to or landed directly on two cloned R genes(xa25,and Xa26),which demonstrated the relatively high resolution of GWAS.Moreover,some novel significant associations on chromosomes 1,6,7,8 and 10 were detected.3.Some loci associated with resisatance for bacterial blight identified by GWAS were confirmed by gene mapping using F2 populations derived from resistant varieties Shangujiu and Tedingyouxuan with Jingang 30.4.CAPS markers for resistance against C5 and IV were developed based on the non-synonymous mutant SNPs according to GWAS analysis.Our results in this study will provide novel information for rice breeding and gene fine mapping for bacterial blight resistance.