Molecular Genetic Dissection Of Rice Grain Quality And Identification Of Grain Shape Mutants In Rice Radiation Induction Population

One of the major targets of rice breeding is the improvement of grain quality. Improvement of grain quality based on the conventional breeding methods is inefficient because the grain quality traits are very complex and easy to be affected by the environments. In the study, linkage map of RILs derived from Nanyangzhan and Chuan7 was constructed and molecular genetic analysis of 9 grain quality traits, including grain length (GL), grain width (GW), length width ratio (LWR), 1000-grain weight (TGW), brown rice ratio (BRR), milled rice ratio (MRR), head rice ratio (HRR), amylose content (AC) and protein content (PC), were conducted according to the phynotypic data across three environments. NILs of the locus controlling major QTLs for traits were developed by marker-assisted selection. Additionally, Nanyangzhan and Chuan7 were irradiated by gamma rays to induce new rice germplasm on grain shape. Main results are as following:1. There were distinct differences between Nanyangzhan and Chuan7 on GL, GW, LWR, TGW and HRR. The RILs population indicated similar bimodal segregations for GL, LWR, TGW and HRR, suggesting there might be a major QTLs controlling these traits; whereas, normal distributions for the rest, indicating quantitative-inherited.2. The genetic linkage map of Nanyangzhan/Chuan7 RILs population was constructed by 185 SSR markers covering all 12 chromosomes, which covered a total of 1585.9cM with an average interval of 8.57cM between adjacent markers.3. Parents and RILs population were planted in Shanghai in 2004, Shanghai and Hainan in 2006. With the data of grain quality collected from two years and two points, 15 main QTLs and 50 pairs epistatic QTLs, 41 main QTLs and 47 epistatic QTLs, and 38 main QTLs and 29 epistatic QTLs were detected in El, E2 and E3, respectively, which influenced GL, GW, LWR, TGW, BRR, MRR, HRR, AC and PC. Among them, five QTLs intervals and two epistatic QTLs were identified repeatedly under different environments.4. Combined QTLs analysis was conducted with the total data of grain quality across three environments. In total of 20 QTLs, including 3 loci with significant Q X E interation for AC, and 21 epistatic QTLs were detected and influenced these 9 grain quality traits. Main QTLs were the most important determinants for all of traits, except that epistatic QTLs explained a larger proportion of the phenotypic variation than M-QTLs for GW. There were three QTLs clusters on chromosome 2, 3 and 6 controlling multiple traits. The later two QTLs cluster are GS3 and Wx loci.5. NILs of the interval of RM3204-RM6283 on chromosome 3 clustering major QTLs for GL, LWR, TGW, MRR and HRR were developed by marker-assisted selection.6. Nanyangzhan and Chuan7 were irradiated by gamma rays. With grain shape variation as the main criterion, 96 and 112 stable mutant lines of Nanyangzhan and Chuan7 including grain, panicle, stem, leaf, fertility and grain quality variations were identified. Among them, 23 and 45 mutant lines of Nanyangzhan and Chuan7 were selected and measured agronomic and quality traits in M₇ and M₈. These new rice germplasms from irradiation mutants were Identified and characterized.