Genetic analysis of grain filling rate in different growth stages of superior and inferior grains in rice

【Objective】 In this paper we analyzed the genetic effects on grain-filling rate for inferior and superior grains of rice at different developmental stages. 【Method】Genetic models of the triploid endosperms including endosperm effect, cytoplasmic effect and maternal effect, and the statistical approaches of conditional genetic variances were used to analyze with semi-completed dialed cross of 5 rice varieties. 【Result 】The results indicated that: (1) Conditional genetic variances could test more genetic variances components than non-conditional variances. (2) Conditional variance results showed:Ⅰ. For the superior grains, the grain-filling rate was mainly controlled by genetic factors. Endosperm effect was more important in the early stage, and cytoplasmic and maternal effects were more important in the middle and late stages. As for the characteristics of the gene effects, the endosperm additive effect took the main role in the early stage and the maternal additive effect took actions in the whole filling stage. Ⅱ. The grain-filling rate of inferior grains was more influenced by environment in early and late stages, the endosperm additive × environment interaction was dominant in the early stage and cytoplasmic×environment interaction was dominant in the late stage. Only in the middle stage gene effect was dominant, and the endosperm additive variance and maternal additive variance were significant, with the endosperm variances more important. 【Conclusion 】 So, it can be concluded that the selection for superior and inferior grains should be conducted in the early and middle stages respectively based on endosperm additive variances. High photosynthesis rate of maternal plants in the late stage can increase grain-filling rate of the inferior grains.