Improvement Of Grain Quality Of G46B By Molecular Marker-assisted Selection

Improvement of the grain quality of maintainer line and its CMS line is the key to improve grain quality of indica hybrid rice. G46B is an excellent maintainer line of indica rice with high general combination ability and well adaptability. But the grain quality of G46B and its combinations are not so good, and the main problems are its high chalkiness, high amylose content, hard gel consistency and poor eating quality.In this studying, some improved G46B maintainer lines on grain quality was obtained by molecular marker-assisted selection to offspring of G46B / Lemont. The marker 484/485 tightly linked to Wx gene is correlated to amylose content. 32 SSR primers were used for genetic background screening .The donor parent is Lemont, a japonica rice with good grain quality originated from United States of America. The receptor parent is G46B. The main results are as follows:1. Selected by 484/485, 26 plants with heterozygous genotype(H) were obtained inand 47 in BCiFi , 86 in BC3Fi . 40, 9, 11 plants with homogeneous genotype of Lemont(L) were obtained in BCiF2 ,BC2F2 and BC3F2 respectively. Serious distorted segregation of 484/485 inclined to G46B was occurred in the selection to the offspring groups of (BCn)Fi and (BCn)F2 of G46B / Lemont.2. Being selected by 484/485, the plants with genotype H were screened by 32 SSR primers on whole genome . The plants with high semblable rate and similar agronomic characters to G46B were used to be back-crossed with G46B. The results showed that the average semblable rate with G46B was 48.25% in BC1F1, 68.82% in BC2Fl5 83.95% in BC3F1 . For those plants with Lemont genotype(L) selected by 484/485 in BC1F2, BC2F2 and BC3F2, the averagesemblable rate with G46B was 64.4% ,80.79% and 85.66% respectively.3. The improved plants on amylose content have been obtained through analysis to amylose content in BC1F2, BC2F2and BC3F2. The plants' amylose content decreased 5.4% ,1.62% and 1.82% in BC1F2 , BC2F2 and BC3F2 respectively.4. In the BCnFn groups, some improved plants were obtained with better quality on length/width, chalky rate and chalk area. The average length/width of BC1F2, BC2F2, and BC3F2 were increased by 0.20, 0.09 and 0.05 over G46B respectively; the chalky rate were decreased57.07%, 13.25% and 17.60% respectively and the chalk area were decreased 4.22%, 0.24% and 1.00% respectively.5. Analysis to grain quality of the 3 genotype(G, H, L) plants in the (BCn)F2 groups selected by 484/485 showed: (1) the genotype of G46B- "G" >the heterozygous genotype "H">the genotype of lemont- "L" on amolyse content, chalky rate and chalk area. (2) the genotype of "G"