Abstract:

The poor grain plumpness is the general question in modern large panicle rice cultivars. The relationship of grain plumpness with grain yield and grain quality has not been reported. The field experiment was conducted in 2003–2004 to research the dynamic changes of grain filling rate, grain plumpness, relative plumpness and their relationship with grain yield and grain quality using the rice cultivar of Yujing 6 with chemical regulation treatments of T27, T23, PR1 and T30 (the check is water) at 5 days before heading. The grain relative plumpness is expressed by the percentage of 1000-grain weight of inferior grains to superior grains in one panicle of rice. The result indicated that the super-grain filling rate was 256% more than that of inferior-grain at early grain-filling stage (5–12 days after heading), and the filling rate of inferior-grain was 16.67% and 154.55% more than that of super-grain at mid-filling stage and later-filling stage respectively. The dynamic changes of grain plumpness and 1000-grain weight in superior grain were also different from those in inferior grain. The grain relative plumpness reduced rapidly at 5–12 day, rose rapidly at 12–19 days and rose slowly at 19–32 days after heading. The grain relative plumpness of PR1 treatment was higher than that of CK and other treatments obviously. There were significant positive correlation at P=0.05 or P=0.01 between grain relative plumpness and mean 1000-grain weight, economic coefficient, theoretical yield and true yield, brown rice percentage of inferior-grain, significant negative correlation at P=0.05 or P=0.01 between grain relative plumpness at 19–32 days after heading and chalky percentage, chalky area, chalkiness, and significant positive correlation between the grain relative plumpness at 19 days after heading and milled rice percentage, head rice percentage of inferior-grain. The results suggest that the Grain relative plumpness is a suitable index to express the relationship between super grain and inferior grain in one panicle.

Key words: Rice, Grain relative plumpness, Grain filling rate, Yield, Grain quality, Chemical regulation