Developmental Genetic Analysis For Nutrient Quality Traits Of Rice (Oryza Sativa L.) Across Environments

Analysis of endosperm, cytoplasm and maternal effects and genotype x environment (GE) interaction effects for rice nutrient quality traits of indica rice (Oryza sativa L.) in different environments was conducted by using the developmental genetic models for quantitative traits. The mating design used by this experiment was a NC II design with 12 parents. Seven cytoplasm male sterile lines were Zhexie 2, Xieqingzao, Zhenan 3, Zhenshan 97, Gangchao 1, V20 and Zuo 5 and five-restorer lines were T49, Cezao 2-2, 26715, 102 and 1391. Seed samples of parents, F, and F2 were collected at four developmental stages (7, 14, 21 and 28 days after flowering). Quantitative traits of rice nutrient quality analyzed were protein content (%) and amino acid content of rice (%), which were measured from two replications by using the method of near-infrared reflectance spectroscopy with NIRSystems model 5000 monochromator for each sample of parents, F,s and F2s at four developmental stages in rice. The main results were as follows:The results of conditional genetic variance components showed that the new expression of quantitative genes in endosperm, cytoplasm and maternal plant for protein content of rice was detected at all different filling stages of rice. The genetic main effects were predominant for protein content at early and late filling stages, however, the genotype x environment interaction effects played an important role at middle filling stage and mature stage. With the rice maturing, the new expression of genes related to protein content of rice was gradually enhanced. Net genetic effects were mainly come from the expression of maternal plant genes, cytoplasm effect was little on the performance of protein content of rice at early filling stage. The endosperm additive x environment interaction and maternal additive x environment interaction effects played a comparative important role at middle filling of rice, while the maternal additive effect, cytoplasmic effect and their interaction effects were more important at late filling stage. At mature stage, endosperm additive x environment interaction and maternal additive x environment interaction effects were significant for protein content of rice; dominance effects and cytoplasmic effect existed but the influence were not large at this filling stage. Genes related to lysine content of rice were more active at early filling stage of rice, new expression with additive effect was mainly come from maternalplant and endosperm genes. At late filling stage of rice, maternal additive effect, endosperm additive effect along with their interaction effects were predominant for this nutrition quality trait. At mature stage, expression of genes was weak, except for genes with endosperm additive effect. For other amino acid content of rice, such as content of threonine, isoleucine and leucine, the related genes expression was still active at mature stage, especially for the endosperm additive * environment interaction and maternal additive * environment interaction effects.The results of heritability analysis showed that the narrow sense heritability for protein content and amino acid content traits of rice was large. The general narrow sense heritability for protein content was large at early filling stage. It was indicated that the selection effect at this filling stage of rice was more stable than that at other stages. The narrow sense heritability components of endosperm, cytoplasm and maternal plant were significant at middle filling stage, and endosperm interaction heritability was more important. The genes related to protein content of rice expressed actively at later stage and mature stage, but the expression was easily influenced by environment conditions. The maternal narrow sense heritability for lysine content of rice was larger at early, middle and late filling stages, while endosperm interaction heritability was more important at mature stage. Cytoplasm heritability was also significant at middle and late stages. The significant narrow sense interaction heritabi...