Mapping of QTL Controlling 6 Panicle Traits of Rice under Direct-sowing Environment

To characterize the genetic basis of 6 rice panicle traits as well as their relationships with each other,mapping of quantitative trait locus(QTL) was conducted with a RIL(recombinant inbred line) population derived from a cross between ’Lemont’(japonica var.) and ’Teqing’(indica var.) under a direct-sowing field experiment.A total of 19 QTL were identified,numbers of QTL for each trait varied from 2 to 4,and variations explained by each QTL ranged from 4% to 22%.Three chromosome regions were found to have pleiotropic or linked effects on multiple traits.The two regions RM212-RM104 on chromosome 1 and RM263-RM221 on chromosome 2 showed multiple effects on 3 or 4 traits of grain yield per plant,number of spikelets per panicle,panicle setting density and number of secondary rachis branches in the same direction,and the Teqing genotype increased all the trait values at the two regions,providing a genetic explanation for the positive correlations among the four traits.The other region near RG1022 on chromosome 11 showed multiple effects on panicle setting density and panicle length in the opposite directions,and at this region the ’Teqing’ genotype increased the trait value of panicle setting density but decreased the trait value of panicle length,also providing a genetic explanation for the negative correlation between these two traits.In addition,the QTL identified in the present study and previous studies with different mapping populations under vary environments were compared and the application of some stably expressing QTL for high yield breeding programs in rice were discussed.