Difference Analysis on Grain Weight and Seed Setting Rate of Different Grain Positions at Panicle Between Two Panicle Types of Japonica Rice

In order to explore the formation causes of rice quality differences of different panicle varieties,taking three japonicavarieties with erect panicle and three with curved panicle as materials,the differences of grain weight and seed setting rate between different grain positions of two panicle types were analyzed.The results showed that the difference of panicle traits between erect panicle type and curved panicle varieties was obvious; panicle types had no direct correlation with varieties for grain weight and seed setting rate.The variation in grain weight and seed setting rate of grains at the different positions within a panicle was closely related to the flowering order of rice grains on the rachis branches.Generally,grain weight and seed setting rate on the branches at the upper part of a panicle exhibited the greatest,at the middle part the middle,and at the basal part the least.Grain weight and seed setting rate for the grains on a primary branch were greater than those on a secondary branch at the same part of a panicle.Grain weight and seed setting rate for the grain 4,5and 6on the primary branch showed the highest,the grain 2showed the lowest.Grain weight and seed setting rate were the least for the second grain and the greatest for the first grain on a secondary branch within a panicle.The significant difference was found in grain weight among grains located on different rachises(primary and secondary rachises)and panicle position(top,middle and bottom)of rice.The variation in grain weight and seed setting rate of grains at the different positions within a panicle in erect panicle type varieties was greater than that of the curved panicle type varieties.