Study On Developmental Genetics Of Yield-formation In Three-line Indica Hybrid Rice(Oryza Sativa L.)

Developmental genetic patterns of several main yield-forming traits, including shoot dry matter weight, culm-sheath dry matter weight and leaf dry matter weight per plant as well as plant height and stem tiller number were studied in two groups of three-line indica hybrid rice(Oryza Saliva L.) derived from NC II cross by using additive-dominant developmental genetic models and corresponding statistical methods. It indicated that the developmental patterns of the main traits of yield formation was fitted to Logistic growth equations. The results of unconditional genetic variance analysis showed that most of the traits were mainly controlled by dominant effects at different developmental stages. The dominant effects were prevailing at early period for the culm-sheath dry matter weight per plant, but additive effects were pronounced at middle developmental period, and the two effects were equally important at later developmental period. The conditional genetic analysis demonstrated that the expression of additive effect genes for the dry matter weight of shoot seldom exhibited, while dominant effect genes were continuously detected in two years with the most active expression especially at middle period. The additive and dominant effect genes showed different expression for the culmsheath dry matter weight per plant, the former became more active as plant growth and development processed, while the latter tended to stop; Additive effect genes were spasmodically expressed for the leaf dry matter per plant, but the dominant effect genes for the trait were continuously expressed; The additive and dominant effect genes for plant hight were alternatively expressed; The dominant effect was prevailing in stem tiller number. The expressions of additive effect genes for the dry matter weight of shoot and the stem tiller numberwere affected by environment and genotype interaction, but the expressions of dominant effect genes for the t~抩 traits were not significantly affected by the interaction as mentioned above. Heritabilities analysis showed that the conditional and unconditional narrow-sense heritabilities of the traits concerned were different in various stages of development, but the two genetic parameters showed the same trend: they were higher at later period than at earlier one. Heterosis analysis indicated that the unconditional heterosis increased as plant growth and development proceeded for the dry matter weight of shoot, the culm-sheath dry matter weight and the leaf dry matter weight. The unconditional heterosis was the strongest at middle developmental stage for plant height and the stem tiller number. Especially there were significantly negative heterosis at later developmental stage for the culm-sheath dry matter weight, which was attributed to the full transportation of culm-sheath dry matter to the panicles suggested in the study on cultivated physiology. The conditional heterosis gave a reasonable explanation for the unconditional one, which further showed that genes were selectively expressed in the whole courses of yield formation. The analysis of genetic correlation between the final biomass production and the other traits concerned at different developmental stages showed that there was a strong dominant effect between the final biomass production and the dry matter weight of shoot. Dominant correlation decreased between the final biomass production and the culm-sheath dry matter weight as the plant growth and development proceeded, and negative dominant correlation were detected became stronger and stronger in later developmental period. For leaf dry matter weight, additive correlation kept decreasing and dominant correlation kept increasing at early growing period, additive correlation tended to be stable and dominant correlation tended to decrease at middle stage, both additive and dominant correlations kept stable at later stage. There were different additive correlations at early and late developmental stages between plant height and the final biomass production, and positive dom...