Abstract:

Plant type improvement is one of the important methods in rice super high yield breeding, and the erect panicle type is core target of northern japonica rice plant type improvement. The filling properties of grains on different positions in 5 panicle types of rice cultivars were studied in this experiment with a randomized block design, and the data were simulated and analyzed with Richards equation W=A/(1+Be^-bt)^1/N. The results indicated that for a erect panicle cultivar, the filling of the secondary branch grains at the middle and basal parts was significantly inhibited by the primary branch grains at the upper and middle parts because the big erect panicle varieties have more spikelets than those of curved panicle varieties. The grain filling peak value of the secondary branch grains at middle and basal parts in erect panicle cultivar Shennong 265 was smaller, and the time to peak value was later. The maximum filling rate in basal secondary branch grains was about half of that in upper primary branch grains, and the time to maximum filling rate was 10 d later, but after that time the filling rate slowed down, and the dynamic curve of grain weight was close to the linearity, at last the grain weight was also close to that of other positions. When the grains per panicle and grain density of erect panicle cultivars reached to 170 grains/panicle and 10 grains/cm, respectively, there was obvious difference in grain filling of different grain positions between big erect and semi-erect panicle types of rice cultivars, but the middle and basal secondary branch grains could finish normal grain filling, suggesting that erect panicle type cultivars can overcome the negative effect from increased grains/panicle and grain density on a certain extent, which is an important physiological basis for yield potential increase. As for the curved panicle cultivars, the primary branch grains at the upper and middle parts mainly inhibited the middle secondary branch grains in a panicle, and the influence was less than that of the erect panicle cultivars.

Key words: Rice, Panicle type, Position, Grain-filling