Pleiotropic Analysis Of3Heading Date Genes In Rice

Heading date is a key factor determining the regional and seasonal adaption of rice, which is ofsignificance for the yield performance. Therefore, it plays a principal role in high-yield breeding of riceto shed light on the molecular mechanism for flowering and the genetic relationship between headingdate and yield traits. Based on the qunatitative trait locus (QTL) mapping for yield traits and headingdate in populations derived from the indica rice cross Zhenshan97B/Milyang46in our previous studies,selfed progenies of Zhenshan97B3/Milyang46was selected to develop populations with stepwisesegregating segments in an isogenic genetic background for the pleiotropic analysis of heading dategenes in rice. On the one hand, aimed at cloned RFT1and Hd1, two key genes for heading date in riceon the short arm of chromosome6, the multiple effects of two regions, covering RFT1and Hd1respectively, on heading date, plant height and thousand-grain weight were analyzed, and theirinteraction was detected as well. On the other hand, targeted at a minor-effect QTL for heading date,named qHd1, identified on the long arm end of chromosome1in this study, further researches werecarried out, including the validation of the qHd1effect on heading date, the shortening of its confidenceinterval and the analysis of its effects on yield traits. The main results were summarized as follow:1. Two BC2F5populations segregated in the regions harboring heading date gene RFT1-Hd3a andHd1in an isogenic genetic background were constructed using Zhenshan97B as the recurrent parentand Milyang46as the donor parent. QTLs for heading date, plant height and thousand-grain weightwere detected using Windows QTL Cartographer2.5. In addition, four homozygous combinations ofRFT1-Hd3a and Hd1were classified based on the genotypes of Si2944tightly linked to RFT1-Hd3aand the Hd1gene marker Si9337, and the phenotypic differences among the four groups were analyzed.QTLs were detected for each of the three traits analyzed in both regions, which did not interact witheach other. It was also shown that the effects of the Hd1region were always larger than that of theRFT1-Hd3a region.2. Two BC2F6populations and two derived F2:3-type populations segregated on the long arm ofchromosome1in an isogenic genetic background were used for QTL analysis for heading date. Aminor-effect QTL was detected in the interval RM11982-RM12138. Five populations carryingoverlapping segregating region in this interval and five sets of near isogenic lines derived wereestablished and used to delimite qHd1to a761Kb interval RM12063-RM12138, combined with theanalysis of the phenotypic variation among different genotypic groups in the same population and thecomparison among the segregating regions presented in the different populations and the overlapping ofthe segregating segments. Then the effect of qHd1region on yield traits was analyzed, which showedthat this region exerted pleiotropism on the number of panicles per plant, the number of filled grains perpanicle, the number of spikelets per panicle and grain yield. And the direction of the additive effect onheading date and yield traits was identical in the qHd1region, in which the enhancing allele was fromZhenshan97B.