Fine Mapping And Molecular Breeding Utilization Of Rice Grain Shape Related QTL

Rice is one of the most important food crops in China and a staple food for more than half of the world's population.Therefore,high yield and stable yield of rice is extremely important for Chinese food security.1000-grain weight is one of the key agronomic traits affecting rice yield,which is mainly determined by the length,width and thickness of grain,rice grain type is closely related to quality traits.Therefore,the isolation and cloning of grain-related QTLs and major genes are vital for rice yield and quality improvement,and ensuring food security in China.In this study,the high quality large hybrid rice restorer line material Ya 2115 and the small grain type super rice variety yuxiangyouzhan?YXYZ?were selected as the parents,QTL mapping of grain length and grain width traits was performed by high-throughput sequencing of F₂ population plant analysis.In the BC₁F₂ isolated population derived from extreme grain size plants,two main QTLs qGW2.1 and qGL2controlling rice grain width and grain length respectively were further fine mapped through chromosome fragment overlap method,and the candidate genes were predicted and analyzed at the same time.The genetic effects and molecular design breeding between the major QTL and genes were carried out,and the main results were as follows:1.A total of 6 grain width and grain length QTL locis were found by QTL analysis of F₂ population of Ya 2115 and YXYZ.Two grain width QTLs were isolated and qGW2.1 was the dominant QTL with an additive effect value of 40.Among the four grain length-related QTLs,qGL2 was the dominant QTL locus with an additive effect value of 17.03.2.The BC₁F₂ segregating population constructed by backcross of extreme grain size plant line with Ya2115 or YXYZ and was used to fine mapping of qGW2.1 and qGL2 through chromosome fragment overlap method.The main QTL locus qGW2.1was located on the short arm of chromosome 2,within a physical distance of 66.9kb between the AM179 and AM487.Two grain width major gene GW2 and OsUBP15are located in this interval.By the same method,qGL2 was finely mapped to the physical distance of 247.2 kb between AM491 and AM493,and the candidate genes in the interval region were analyzed and predicted.3.The genetic effects between qGW2.1 and GL7 were investigated in the BC₁F₂population.It was found that qGW2.1 and GL7 regulate the grain type through independent pathways,and qGW2.1 plays a major role in regulation.Besides,when the combination is"22/11"genetic background contained qGW2.1 and GL7,the plant show highest length-width ratio and the rice grains were more slender.4.Molecular polymerization breeding of qGW2.1,GL7,Wx gene and aroma gene Badh2 was carried out,and combinations containing different genotypes were screened.The effects of different combinations on grain size and chalkiness were analyzed.It was found that the combination of genotype“22/11/11/22”was most beneficial to the breeding of high quality and high yield rice varieties.