Abstract: In the present paper , the relationship between root vigor and grain-filling characteristics were studied, in which three two-line super hybrid rice，Yue-za 122,Yue-za 889,and Yue-za 922, as well as their restorer lines R122, W889,W922 and P/TGMS line GD-1S were used. The results showed that, a) The maximum root bleeding intensity was achieved at different grain-filling stage for the rice hybrids and their parental lines. It occurred at heading for Yue-za 889 and Yue-za 922 and the restorer line R122, and at 5 days after heading(DAH) for Yue-za 122 and W922, but 10 DAH for W889 and GD-1S. The root bleeding intensity consequently declined for all the hybrids and their parental lines except for GD-1S, and its sharp-down point occurred at 15 DAH. b) The fertilized grain-root activity of hybrids was positively and significantly correlated with their parental lines. It suggested that hybrids with high fertilized grain-root activity can be developed by using parental lines with high fertilized grain-root activity. c) The super hybrid rice and their restorer lines had two-period grain-filling phenomenon to some extent, and the maximum grain-filling rate was at about 15 DAH for the superior grains, but at about 30-35 DAH for the inferior grains. d) The grain filling rate of superior grains was significantly correlated with three root vigor indices, ie. root bleeding intensity, spikelet-root activity, and fertilized spikelet-root activity, respectively, only at 15 DAH. The grain-filling rate of inferior grains was significantly correlated with the three root vigor indices at 10, 15 and 20 DAH. Developing super rice hybrid with strong root vigor and maintaining and enhancing its root vigor at the grain-filling period through cultivation measures, could be helpful in solving the problems of two-period grain-filling phenomenon and poor grain filling of super hybrid rice.

Key words: Super hybrid rice, root vigor, grain-filling rate, correlation analysis, fertilized spikelet-root activity