Grain-filling Characteristics of Two Different-panicle Type Rice Cultivars in Heilongjiang Province.

The grain-filling processes at different grain positions of curved-panicle type Longjing 29 and semi-erect-panicle type Longjing 31, two major rice (Oryza sativa L.) cultivars in Heilongjiang Province, were simulated by Richards growth equation, so as to determine the reason of great differences in head rice rate of different rice cultivar among different years and to improve the processing quality of different rice cultivar through cultivation regulation measures. The results showed that the yield of Longjing 29 was slightly higher than that of Longjing 31, but the head rice rate of Longjing 29was significantly lower than that of Longjing 31. More grains on secondary rachis branch resulted in lower plumpness, lower seed-setting rate and lower milled rice rate of Longjing 29. The grain filling rates at the six grain positions of Longjing 31 reached the peaks simultaneously, so the synchronous grain filling characteristic of Longjing 31 was more obvious. The grain-filling rate on the primary rachis branch of Longjing 31 was higher, and it reached the peak in the middle period. Although the grain-filling rate on the secondary rachis branch of Longjing 31 was lower, it early reached the peak. In addition, the middle and late filling period of Longjing 31 was longer, resulting in plump and compact grains on the secondary rachis branch of Longjing 31. After the grain-filling rate on the primary rachis branch was decreased, the grain-filling rate on the secondary rachis branch of Longjing 29 started to be increased greatly, characterized by asynchronous grain filling. In the early grain filling stage, the grains on the upper, middle and basal secondary rachis branch were all significantly suppressed by those on the primary rachis branch of Longjing 29. The initial growth potential and maximum filling rate of grains on the secondary rachis branch of Longjing 29 were all lower. The grain-filling rate on the secondary rachis branch of Longjing 29 late reached the peak. Even worse, the middle and late filling period of Longjing 29 was shorter. Therefore, the grains of Longjing 29 had poor plumpness. Synchronous grain filling led to small difference in grain quality within the same panicle, and this was also the reason for stable head rice rate of Longjing 31 among different years. In contrast, asynchronous grain filling led to great difference in grain quality within the same panicle of Longjing 29. In addition, low temperature often occurred during the fast filling of grains on the secondary rachis branch of Longjing 29. Thus, the head rice rate of Longjing 29 was decreased. [ABSTRACT FROM AUTHOR]