Abstract
The object of this study is to clarlfy which characteristics of sink capacity cause the genetic variation of grain-filling process in rice. The grain-filling parameters, rate and duration of filling as a grain basls, and the slnk-capacity traits, grain length, grain width, number of grains on primary branches, number of grains on secondary branches, seed fertility and nulnber 0L panicles per plant were measured on 29 cultivars with a wide range of their sink-capacity tralts. The results clearly demonstrate that the rate of filling correlates positively with the traits related to grain size and negatively with those related to grain number. Canonical correlation analysis suggests that the correlation between the rate of fllllng and the grain-size traits is predominant. The rate of filling in rice is probably regulated by some factors related to the grain slze. The duration of filling exhibits no significant correlations with the rate of filling, final grain weight and all of the sink-capacity traits. The rate and duration of filling seem to be regulated by different systems.
