Molecular Mapping Of QTLs Conferring Heading Date And Seed Setting In Rice (Oryza Sativa L.)

Rice (Oryza sativa L.) is one of the most important crops that feed almost half of the world’s population. Heading date, one important agronomic trait, is one of the main factors affecting the yield of rice. Detecting and cloning genes related to heading date has vital significance of theory and practice.BC5F2and BC1F2near-isogenic lines derived from the crosses between twenty nine micro-core germplasm collections as donor parent and Nipponbare as the recurrent parent, were used for molecular tagging and QTL mapping for heading date in rice. Using nine of these populations, four QTLs, qHDl-a,qHDl-b, qHDl-c and qHD1-d,were detected on chromosome6with flanking markers RM5745-RM1161, RM3330-RM1161, RM4128-RM3330and RM3370-RM4128for each QTL respectively, and Hdl was found to overlap with these intervals. Other five QTLs, qGHD7-a, qGHD7-b, qGHD7-c, qHD(t)-a and qHD(t)-b were detected on chromosome7, and Ghd7was found to overlap with the interval of qGHD7-a, qGHD7-b and qGHD7-c. Through the comparison, QTLs qHD(t)-a and qHD(t)-b were found to overlap with the interval of QTL Hd(t).These results will lay a solid foundation for further cloning and functional analysis of the candidate genes, and provide theoretical support for molecular breeding of heading date in rice.The low seed setting is one of the major hindrances affecting grain yield in rice. One of the main reasons that cause low seed setting (spikelet fertility) is male sterility or pollen abortion, which has been frequently observed in advanced progenies of rice. In the present study,149BC2F6individuals with significant segregation in spikelet fertility were generated from the cross between N040212(indica) and Nipponbare (Japonica) and used for primary QTL mapping. And three QTLs, qSS-1, qSS-7and qSS-9on chromosomes1,7and9respectively, were detected to be associated with seed setting. Recombinant analysis and physical mapping information from publicly available resources showed that the qSS-1, qSS-7and qSS-9loci were mapped to an interval of188kb,701kb and3,741kb respectively. Then, QTL qSS-1was further fine mapped to a93.5kb interval by using BC2F7population of1849individuals, and there are sixteen putative genes in this region. Pollen vitality tests and artificial pollination indicated that the male gamete had abnormal pollen while the female gamete was normal, which indicated that low seed-setting rate related to qSS-1may be caused by abnormal pollen grains. These results will provide a firm foundation for further cloning and functional analysis of the target gene governing spikelet fertility.