抄録
We examined the involvement of genetic and environmental factors in the variations and associations of the rate and duration of grain filling and the final grain weight in rice cultivars, instead of the simple phenotypic correlation and variance. The estimations were conducted by analyses of variance and covariance in a two-way classification, using ten rice cultivars cultivated under three environments at different locations and years. Also examined were the differences in these parameters for various grain positions on a panicle, the grains on primary rachis-branches and the grains on secondary rachis-branches. In both grain positions in a panicle, the rate and duration of grain filling differed widely with the environment and cultivar, and showed a very high negative environmental correlation between these two traits. The final grain weight (= filling rate × filling duration) showed a much smaller variation due to environmental fluctuations compared with the rate and duration of filling, which reflects the negatively associated environmental changes in the rate and duration of grain filling. The duration of filling, especially that in the grains on secondary rachis-branches, was more influenced by non-genetic factors than the rate of filling. The genetic correlation between the rate and duration of grain filling was not so high. The final grain weight, on the other hand, was strongly and genetically correlated only with the filling rate, not with the filling duration. This may have resulted from some constraints which do not allow longer filling durations to attain higher final grain weights.
