Abstract:

Low temperature (LT) after flowering impacts greatly on grain filling, decreasing rice quality through extended filling duration, shortened filling rate, and decreased physiological activity. Indica-japonica hybrid rice has been applied widely in production practice, due to high yield potential. However, there has been little study on the effect of LT on endogenous hormones in indica-japonica hybrid cultivars at filling stage. In the study, four varieties, i.e. two indica-japonica hybrid rice (Yongyou 538, YY538; Yongyou 17, YY17), one indica rice (Zhongzheyou 1, ZZY1) and one japonica rice (Zhejing 88, ZJ88), were treated with those low temperature treatments at different grain filling phases, to compare endogenous hormone levels in treatments, aiming to reveal the influence of low temperature on grain filling and the response of endogenous hormone in grains to low temperature. The effect of LT on grain filling after different flowering stage appeared significantly at early grain filling stage, while a little difference was observed at later filling stage, compared with CK. Furthermore, the influence on grain filling was found higher in Yongyou17 and Zhongzheyou 1 than in Yongyou 538 and Zhejing 88. Compared with the contract, LT after flowering at early stage significantly decreased grain filling and prolonged grain filling duration in Yongyou 17, but not in Yongyou 538. Based on the effect of LT on grain filling process and its relation with endogenous hormones contents, it might be deduced that the normal grain filling should be ascribed to the significantly reduced GA3 content and the slightly increased IAA, ZR contents in developing grains of Yongyou 538 at early and middle grain-filling stage. On the contrary, the significantly reduced IAA, ZR contents and the significantly increased GA3, ABA contents in Yongyou17 could restrain grain development. It should enhance grain filling of rice encounted LT by selected measures adjusting hormone in practice management.

Key words: Indica-japonica hybrid rice, Grain-filling stage, Different low temperature, Hormones