Genetic analysis and molecular mapping of QTLs associated with resistance to bacterial blight in a rice mutant, SA0423

Abstract

Bacterial blight disease, caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most serious diseases in rice producing areas. SA0423 is a broad-range resistance mutant selected from a popular japonica-type variety, TNG67, using sodium azide mutagenesis. Genetic analysis and QTL mapping of SA0423 were performed using the descendants obtained from crossing with Taichung Native 1, a susceptible and well-known indica variety, by challenging with a Taiwanese Xoo isolate, XF89b. Genetic analysis displayed that the resistance of SA0423 is regulated by quantitative trait loci (QTLs) with incomplete dominance. A linkage map covering 12 chromosomes and consisting of 148 SSR as well as 3 InDel markers was constructed. Three QTLs are identified on chromosomes 11, 8 and 6 and account for 21.1, 11 and 9.6 % of the observed phenotypic variance, respectively. Three QTLs are localized to 6, 7 and 14 confidence intervals, respectively. These QTLs contribute to approximately 47 % of the total phenotypic variation of the F-2 population. No epistatic effect could be detected among the three QTLs. Our results provide a suitable source of potential disease resistance genes and establish a system for improving rice bacterial blight resistance through marker-assisted selection.