Genetic variation of typhoon-induced spikelet sterility in introgression lines with genetic background of Indica group rice (Oryza sativa L.) variety IR 64

Wide variations of typhoon-induced spikelet sterility and days to heading (DH) were found among 317 introgression lines (INLs) originating from new-plant-type varieties with a genetic background of Indica Group rice variety IR 64. Sterility was induced by continuous dry winds from the typhoon. The most seriously affected were 194 INLs with DH ranging from 83 to 86 days. Positive correlations with the spikelet sterility score (SSS) were found for culm length (CL), panicle length (PL), and panicle weight (PW). Based on these traits and DH, the 194 INLs were classified into three groups: A1, A2, and B. The means of SSS and four traits (CL, PL, culm and leaf weight (CW), and panicle weight (PW)) were the lowest in group A1, and highest in group B. PN was significantly higher in group B than those in the others. Seven quantitative trait loci (QTL) for SSS were detected on chromosomes (chr.) 1, 2, 4, 7 (two), 8, and 11. Among them, the QTL of chr. 4 was located in the same regions as those of DH, CL, PL, CW, and panicle number (PN). Thus, the region on chr.4 might induce sterility in the INLs by modifying plant architecture, such as large panicles or high plant height with the minor effect of many tillers. The relationships among traits, and the QTLs will be useful information for genetic improvement of tolerance to typhoon damage in rice.