Effects of sowing date on seed setting characteristics of hybrid rice varieties in Sichuan

【Objective】The study investigated the effect of late planting on seed setting characteristics of hybrid rice varieties in Sichuan to improve their drought avoidance and water saving cultivation.【Method】Twenty indica rice varieties were planted at 6sowing dates(Ⅰ.04-10;Ⅱ.04-20;Ⅲ.04-30;Ⅳ.05-10;Ⅴ.05-20;and Ⅵ.05-30).The effect of late planting on seed setting characteristics of different varieties was analyzed.【Result】1)The differences in seed setting characteristics of rice varieties between different sowing dates,varieties and their interactions were highly significant.Seed setting rate and grain plumpness were greatly influenced by sowing date and 1 000-grain weight was strongly influenced by variety.2)All the three seed setting characteristics presented a downward trend after the initial increase as the delay of sowing date.They reached the maximum at phase Ⅲ before significant reduction.The seed setting rates of middle-level and weak-level seeds as well as 1 000-grain weight and grain plumpness of weak-level seeds decreased the most.3)The delay of sowing date to late April was feasible to indica hybrid rice.All varieties tested can satisfy this requirement.If the sowing date was delayed to middle or late of May,Yixiangyou 2115,Dexiang 4103,Ⅱ You 498,Chuanxiang 8108,and Ⅱ You H103 should be chosen.【Conclusion】In order to guarantee the yield of rice,appropriate sowing date and suitable varieties should be selected.