Chilling damage during the heading, flowering stage of rice is common on the high-altitude Panxi plateau in the mountainous region around the Sichuan basin and poses a great threat to japonica and indica rice production in this area. In the present study, we explored the effects of low-temperature stress due to delayed sowing and natural low temperatures in the late growing period on the grain-filling and yield of three indica rice and three japonica rice varieties in field experiments. The results demonstrated that the effects of low temperature due to delayed sowing on the grain-filling period and yield of indica rice during the mid to late growing period were greater than those of japonica rice. There was only one grain-filling peak at different grain positions in indica rice, and different grain-filling positions in japonica rice were classified as asynchronous grain-filling. Compared with that under the normal sowing date, japonica rice had superior cold tolerance under delayed sowing, which provided rapid growth of superior rice grains in the early grain-filling period, earlier start time of grain-filling, and the higher average grain-filling rate at 8-12 d after heading. The grain-filling and seed-setting of indica rice with an inferior cold tolerance mainly occurred in the second rapid grain-filling period 21-30 d after heading. The reduction in the effective panicle number and the seed-setting rate of rice under delayed sowing conditions, especially the decrease in the seed-setting of the secondary branch, resulted in a significant decrease in rice yield, and this decrease was more pronounced in indica rice.
Key words: Indica rice, japonica rice, delayed sowing, low-temperature stress, grain-filling characteristics, rice yield
|
