Fine-mapping Of QTL QGL-3 For Grain Length In Rice

Rice（Oryza sativa L.）is one of the most important food crops in the world,and also is the ration of about 60%of the population in China.In recent years,rice geneticists and breeders have carried out a series of studies around rice yield and quality traits,analyzing the genetic regulation mechanism,and cultivating new rice varieties with high yield and quality,which not only met the needs of consumers for high-quality rice to a certain extent,but also made important contributions to ensuring food security.However,with the continuous increase of population and the decrease of cultivated land,consumers’ demand for high-quality rice is increasing.Therefore,it is urgent for rice breeders to cultivate high-yield and highquality rice varieties.The three elements of rice yield include the number of effective panicles,the number of grains per panicle and grain weight.Grain size plays a decisive role in grain weight,and also affects the appearance quality of rice.Therefore,analyzing the important gene resources of rice grain size is of great significance to improve yield and appearance quality.The research on the regulation mechanism of grain size will provide an important theoretical basis for cultivating high-yield and high-quality rice varieties.In this study,qGL-3 was mapped to 309 Kb using the population genrated by recipient parent C418 and the donor parent 02428.The main results are as follows:1.Chromosome introgression line CSSL-8601 was selected in the BC5F2 population carring substitutional fragments distributed on chromosomes 2,3,4,6,7,8 and 11,with an average length of 3.3 Mb.2.BC6F2 population was constructed by backcrossing and selfing with recurrent parent C418.Significant difference was found on chromosome 3 using Rice40K chip by detecting the mixed pool of 20 plants with small grains and long grains respectively.Further,five QTLs for grain length and two QTLs related to grain width were comformed on chromosome 3 by QTL scanning.3.The small grain introgression line CSSL-Z5 with fragments on chromosomes 2,3 and 6 was obtained from BC6F2 population by molecular marker assisted selection.CSSL-Z5 was further backcrossed with recurrent parent C418 and selfed to construct BC7F2 population for QTL scanning.The grain length QTL qGL-3-6 was detected in the highly overlapped region with qGL-3.4.Near isogenic lines of qGL-3 was obtained through marker assisted selection in BC7F2 population.There were significant differences in grain length and grain width between NILqGL-302428 and NIL-qGL-3C418.Compared with NIL-qGL-3C418,the hull cell length of NILqGL-302428 was significantly reduced by 21.47%and the cell width was increased by 9.56%,while the difference in the of cells number was not significant,indicating that qGL-3 negatively regulated grain length and positively regulated grain width by inhibiting the increase of cell length and promoting the increase of cell width.5.The recombinant plants were screened in the BC7F2 popolation and selefed to construct BC7F3 population.Comparing the grain length of the recombinant line with overlapping fragments,qGL-3 was finally mapped to 309 Kb.