Analysis Of The Development Genetic Effects For Protein Content And Its Conditional Relationship With Other Quality Traits Of Rice

Seven indica male sterile lines (A) were crossed with 5 indica restorer lines (R), and the factorial mating design was used in this experiment in two years. Seeds of F₁, F₂ and the parents were collected at 7d, 14d, 21d, 28d after flowering, the protein content (PC) of them were examined after they were dried. And the milling quality, appearance quality, cooking quality and nutrition quality traits of the maturity seeds for F₁, F₂ and the parents were also examined. The unconditional and conditional genetic models and corresponding statistical approaches for quantitative traits of triploid endosperm in cereal crops were used for the analysis. The dynamic gene expressive mechanism from different genetic systems for PC of indica hybrid rice were analyzed;and the unconditional and conditional genetic correlations between PC and the quality traits of rice were also disclosed, in a further study the impact of the weight of brown rice (WBR) or the amylose content (AC) on the genetic correlations between PC and the quality traits of indica rice were discussed. The main results were as follows.The results of the developmental genetic effect analysis for protein content showed that the gene expressive effects in different development stages, especially genotype × environment (GE) interaction effects from the genes expression of different genetic systems including triploid endosperm, cytoplasm and diploid maternal plant at all developmental times/stages of rice grain were important for the performance of PC. The results from the conditional genetic variance analysis revealed that the activation of quantitative genes, especially from endosperm and maternal plant genetic systems for the performance of PC were carried or closed during the developmental process of rice grain. The net genetic effects showed that the new expression of quantitative genes for PC was more active at later filling stage (15-21 days after flowering) and maturity stage (22-28 days after flowering) of rice grain. The triploid endosperm, cytoplasm and diploid maternal plant genes expression were different in various development stages. The correlations of additive effects and dominance interaction effects for the performance of PC were significantly positive among different developmental stages. The impact of GE interaction effects for the performance of PC was different;especially for the additive GE interaction effects, which were increased during the performance of PC at the developmental times of rice grain.The unconditional analysis and conditional analysis methods were used to study the genetic relationships between PC and the quality traits of indica rice. The unconditional analysis results showed that PC was significantly negative correlative to the weight of brown rice (WBR), and significantly positive to the weight of milled rice (WMR) or themilled rice recovery (MRR), but was not significantly correlative to the brown rice recovery (BRR). The unconditional genetic correlation were significantly negative between PC and the brown rice length (BRL), the ratio of brown rice length to width (RLW), the ratio of brown rice length to thickness (RLT) of appearance quality;but PC was significantly positive to the brown rice width (BRW) and was not significantly correlative to the brown rice thickness (BRT) or the chalkiness area of rice (CA). The unconditional genetic relation between PC and AC was significantly negative, but was significantly positive between PC and the gel consistency (GC). Analyzed by unconditional method, PC was significantly positive to all of the amino acids of indica rice.When PC was conditioned on WBR (PC|WBR), the genetic relationships between PC and the quality traits of rice were remarkably changed by conditional analysis method;WBR would, hence, notablely influence the genetic relationships between PC and the quality traits of rice. Using conditional analysis methods, all the conditional covariances were significantly positive between PC|WBR and the milling quality traits of rice;the unconditional and conditional analysis of triploid endosperm, cytoplasm and diploid maternal plant genetic systems covariances showed that WBR mainly by affected the cytoplasmic main effects and its GE interaction effects to change the genetic relationship between PC and the milling quality of indica rice. The conditional genetic correlation between PC|WBR and BRL, BRW, BRT were significantly positive, but PC|WBR was not significantly correlative to RLW, RLT or CA;the covarances parameters analysis indicated that WBR might be mostly impacted on the cytoplasmic effects and the maternal plant effects, negatively affected the genetic correlations between PC and BRL, BRW, BRT, but positively affected the relationship between PC and RLW, RLT, and the impact of WBR on the genetic relationship between PC and CA was not notable. WBR could notably affect the relationships between PC and the cooking quality traits of indica rice, and the unconditional and conditional covarances parameters analysis showed that WBR could change the endosperm additive effects, and cytoplasm effects of the pairwise traits;after PC conditioned on WBR, all the genetic relationship were not significant. Comparing conditional analysis results with unconditional analysis results of different genetic systems covarance parameters, WBR mainly throught influencing the endosperm additive main effects, cytoplasmic main effects, cytoplasmic GE interaction effects and the maternal additive main effects, positively affected the genetic correlation between PC and the amino acids content of indica rice, the unconditional genetic correlation, therefore, were larger than those of conditional analysis for the pairwise traits, and all the conditional genetic correlation were significantly positive between PC|WBR and amino acids content of indica rice.After PC was conditioned on AC (PC|AC), all the genetic correlations between PC and the quality traits of indica rice, including different genetic systems genetic relationships were notably changed. The unconditional and conditional analysis of the triploid endosperm, cytoplasm and diploid maternal plant genetic systems covariances showed that, AC mostly by impacting on the endosperm and maternal genes effects, negatively affected the relationship between PC and WBR, WMR, or BRR, but positively affected the correlation between PC and MRR;after PC was conditioned on AC, only the conditional genetic relationship between PC|AC and the WBR was significant. The unconditional and conditional covarances parameters analysis indicated that, AC might be mostly by influencing the cytoplasmic main effects, maternal addition main effects, positively affected the relationship between PC and BRL, RLW, or RLT, and negatively affected the genetic correlation between PC and BRW, but the impact of WBR on the relationship between PC and BRT or CA was not notable;all the conditional genetic relationships between PC|AC and the appearance quality traits of rice were not significant by conditional analysis method. The conditional genetic correlation between PC|AC and GC was significantly positive, but the conditional covariance estimates were larger than those of unconditional;covariances analyzing of different genetic systems revealed that AC was mostly throught the endosperm genetic main effects, cytoplasmic effects and the covariances between endosperm and maternal addition effects affected the correlation between PC and GC. After PC was conditioned on AC, the conditional covariance estimates between PC|AC and lysine content were smaller than those of unconditional analysis, but the conditional covariance estimates between PC|AC and the others amino acids were larger than analyzed by unconditional method;and all the conditional genetic covariances were significantly positive between PC|AC and the amino acid contents;AC might be impacted on the relationships between PC and the nutrition quality mostly by the endosperm addition effects, maternal addition effects, maternal addition interaction effects, covariance between endosperm and maternal addition effects and its GE interaction effects of indica rice.