| We examined the effect of degree of milling on the amylose content of the grain using a japonica rice variety, 'Zhejing 27', and an indica rice variety, 'Zhenong 5'. In a further study seven indica male sterile lines (A) were crossed with 5 japonica restorer lines (R). Seed of 35 F1S (A×R), the parents and F2 generations were collected at 7, 14, 21, 28 and 35d after flowering. Grain quality traits analyzed were amylose content (AC), gel consistency (GC), protein content (PC), lysine (Lys) content, methionine (Met) content, leucine (Leu) content, isoleucine content (Ile), phenylalanine (Phe) content, valine (Val) content and threonine (Thr) content. Two models for developmental genetics and their corresponding statistical approaches for quantitative traits of triploid endosperm in cereal crops were used for the analysis. The first was the unconditional genetic model, which refers to the analysis of cumulative measurements along the developmental stages, while the second was the conditional genetic model, which refers to the analysis throughout the developmental stages. The main results were as follows:1. The amylose content increased by 1.36% in the japonica rice variety "Zhejing 27" and 1.92% in the indica rice variety "Zhenong 5" as degree of milling increased by 10%. Both the japonica and the indica rice variety showed the same response of AC to degree of milling. Furthermore, to minimize error in measuring AC, the need for grain samples to have the same degree of milling and grinding was highlighted.2. AC gradually increased during grain filling in indica-japonica hybrid riceand reached its highest value at the ripe stage (35d after flowering). Hybridities of F1S were not obvious at the initial filling stage (7d after flowering) and early filling stage (14d after flowering), but some hybridities from the middle filling stage (21d after flowering) onwards until ripe stage. In contrast, GC and Met content gradually decreased with grain filling and reached their lowest value at the mature stage. The content of the proteins, Lys, Leu, Ile, Phe, Val and Thr increased as grain filling proceeded and these traits reached their highest values at the late filling stage (28d after flowering), and their hybridities of F1S were greatest.3.Unconditional variance analyses showed that all the cooking quality and nutrient quality traits were simultaneously governed by triploid endosperm effect, cytoplasm effect, diploid maternal plant effect and their genotype x environmental (GE) interaction effects. AC at the early- and middle-filling stages, GC at the initial-, middle- and late-filling stages, contents of Lys, Leu, Ile, Val and Thr at the late filling stage, and contents of Met and Phe at the late- and ripe-stage were mainly governed by genetic main effects, while protein contents were mainly controlled by genetic main effects at the late filling stage. Genetic analyses showed that these traits, including AC, Met content, Leu content, Ile content, Phe content, Val content and Thr content, were mainly governed by endosperm additive effect, while GC and protein content were governed by endosperm additive effect and maternal additive effect. All these traits could be selected in earlier generation(s) in rice breeding programs. There was significant dominance effect for Lys content, and therefore it should be selected in later generation(s).4. Conditional variance analyses showed that there was new gene expression in conditional endosperm, cytoplasmic and maternal plants for cooking and nutrient quality traits. Most new gene expression was found at the initial filling stage (0-7d after following) for AC and GC, early filling stage (8-14d after following) for Lyscontent, middle- and late-filling stage (15-28d after following) for Met content, Leu content, Ile content, Phe content, Val content and Thr content, and the greatest number of genes were activated during these stages. Conditional genetic system analyses showed conditional main effect governed GC at initial- and mid...
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