The Genetic Effects Analysis And Molecular Predicting Of Quality Traits Of Indica Rice (Oryza Sative Indica L.)

Rice is one of the most important food crops in the world which nourished about a half of global population.With the development of agricuture,greater demand is put on forward for food production due to decreasing field and increasing population.Also because of improving of social economy and living standard of people,high quality rice is demanded.While rice quality traits were typic quantity traits,exhibited complicated inheritance,which made it more difficult to study genetic effects than quality traits.However,it is important to study their genetic effects and early prediction for rice quality of rice.The experiment was designed in NCâ…¡with 13 females and 19 males of indica rice(Oryzas sativa ssp.indica).Seven cytoplasmic male sterile(CMS)lines used as females were Zhenshuan 97A, Jin 2A,Chuanxiang 21A,Jinxiang 1A,Jinxiang 2A,Q 2A and Mianxiang 5A,and ten restorer lines used as males were N 45,Jinhui 10,Jinhui 34,Jinhui 33,R 21,R 27,Jinhui 13,Jinhui 12,Jinhui 35 and R 2727 in 1sets.And nine CMS lines used as females were Zhenshuan 97A,Jin 2A,Chuanxiang 21A,â…¡-32A,G 46A,K17A,Jin 23A,Mian 5A,and D 62A,and nine restorer lines used as males were Mianhui 725,Shuhui 527,Taiyin 1,IR 661,IR 26,Minghui 63,Ce 64,Yanhui 559 and Luhui 17 in 2sets.The rice quality traits analyzed in the studies were grain length(GL),grain width(GW), grain thickness GT),brown rice length(BRL),brown rice width(BRW),brown rice thickness (BRT),head rice length(HRL),head rice width(HRW),head rice thickness(HRT),chalk rate(CR), chalk degree(CD),brown rice percentage(BRP),milled rice percentage(MRP),head rice percentage(HRP),Amylose content(AC)and protein content(PC)for parents,F₁s and F₂s in different environments.Analysis of seed,cytoplasmand maternal effects and genotype×environment(GE)interaction effects for rice quality traits of indica rice was conducted and the genetic correlation analysis among rice quality traits was made by using a genetic model including GE interaction effects for quality traits of endosperm in cereal crops,and effect-increasing loci for these quality traits screened by SSR markers were used in their prediction using two-group method and three-group method respectively,and corresponding prediction model based on three-group method was also established.The main result were as follows:1.The rice quality traits of indica rice were simultaneously affected by GE interaction effects as well as the genetic main effects from seed,cytoplasm and maternal genes.GL,GW,BRL,BRW, HRL,HRW,HRT,CR,CD,HRP and AC were mainly controlled by the genetic main effects,and GT,BRT and BRP were mainly affected by GE interaction effects.The genetic main effects and GE interaction effects were similar for MRP and PC.These results indicated that the expression of genes for GL,GW,BRL,BRW,HRL,HRW,HRT,CR,CD,HRP and AC were steady in diferent environments,while those for GT,BRT and BRP were more easily influenced by the environment conditions.2.The seed effects were more significant than others for GL,GW,GT,BRL,BRW,HRL,HRW, CR,CD,MRP,HRP,AC and PC,and maternal effects were larger for BRT,HRT and BRP.All quality traits of indica rice were mainly controlled by seed additive effects,while MRP was also significantly affected by cytoplasmic effects.The analysis of GE interaction effects showed that maternal additive effects for GL,GT,BRT,HRT,BRP and AC,seed additive effects for BRL,BRW, HRL,HRW,CR,CD,MRP,HRP and PC.Seed dominance effects for GW was easily influenced by environment conditions.3.The heritabilities were high for most quality traits of indica rice.The general heritability was main for GL,GW,BRL,BRW,HRL,HRW,HRT,CR,CD,HRP and AC,the values(mean of two sets)were 68.81%,63.37%,90.01%,82.29%,80.39%,50.52%,12.22%,75.33%,47.77,55.68%and 79.47%,respectively.But the interaction heritability was more significant for GT,BRT,BRP,MRP and PC,the values(mean of two sets)were 52.15%,49.77%,58.91%,35.89%and 48.05%.4.The correlation coefficients of genetic distance(GD)based on effect-increasing loci(IL) with F₁ quality traits were larger than those based on positive markers(PLs).In Chongqing,the correlation coefficients of GD with PL varied from -0.570 to 0.635,with a mean of -0.062,while the correlation of GD with IL varied from 0.153 to 0.833,with a mean of 0.598.In Luzhou,the correlation coefficients of GD with PL varied from -0.575 to 0.717,with a mean of 0.005,while the correlation coefficient of GD with IL varied from 0.428 to 0.857,with a mean of 0.695.5.ILs were more effective than PLs in predicting hybrid performance of combinations.The predicting values with PLs of different traits ranged from -0.432 to 0.440,with a mean of -0.003. While the predicting values with ILs were from 0.183 to 0.674,with a mean of 0.433.6.The prediction efficiency based on ILs varied with different traits or parents.It was better for prediction efficiency with the same parents in different environments than that with fixed restorer lines and fixed sterile lines or with different parents in the same environment.The predicting values were 0.566,0.401,0.481 and 0.289 predicted with the same parents in different environments,with fixed restorer lines,fixed sterile lines and with different parents in the same environment, respectively.Predicted effects of GL,BRL,HRL,CR,CD,AC and PC were better with fixed restorer lines than fixed sterile lines,while predicted effects of other traitse were better with fixed sterile lines than fixed restorer lines.7.It was not different significantly for predicted effects with ILs between two-group method and three-group method.For prediction with two-group method,the correlation coefficient were 0.570,0.302,0.407 and 0.482,with a mean 0.439,predicted with the same parents in different environments,different parents in the same environment,fixed restore line and fixed sterile line, respectively.For prediction with three-group method,the correlation coefficients were 0.563,0.277, 0.396 and 0.479 respectively,with a mean 0.429,accordingly as the above sequence.8.The predicting effects of some traits demonstrated the promising perspective in heterosis prediction,which would be helpful for rice breeders to improve the efficiency of breeding program. For example,the prediction effects for almost all rice quality traits except for BRP with the same parents in different environments were good,as well as those of GW,BRL,BRW and HRW with different parents in the same environment,those of GL,BRL,HRL,HRW,CR and AC with fixed restorer lines,and those of GW,BRL,BRW,HRW,HRP and AC with fixed sterile lines.9.The predicting results for rice quality traits showed that the larger were the percentage of genetic main effects(V_G)accounted for total genetic effects(V_G+V_GE),the better were the predicting effects using the same parents in different environments,different parents in the same environment,fixed restore lines and fixed sterile lines.On the countrary,the smaller were the percentage of main genetic effects(V_G),the worst were the predicting effects.Consequently, Molecular predicting effects cound be evaluated by genetic main effects to some degrees.