Abstract:

In response to the abnormal high temperature in Yuhang District in 2022, temperature data from four town and street meteorological stations in the district were analyzed to study the effect of high temperature on the setting rate and yield of single season hybrid rice varieties such as Yongyou 1540, Yongyou 12, Chunyou 590, Chunyou 161, and Jiangliangyou 7901. The results showed as following: in 2022, the number of high temperature days with daily maximum temperature higher than 35 ℃ was 65 d, 34 d more than the same period of the last years and the number of high temperature days above 40 ℃ was 32 d. From August 10 to August 23, the period of concentrated heading and flowering of single-season hybrid rice, the temperature in other days were all higher than 38.0 ℃ except for 36.7 ℃ on one day. Due to different the period of heading and flowering, the setting rate of hybrid rice decreased by 13.9-43.3 percentage points when exposed to high temperatures compared with normal temperatures.When the high temperature occurred in the period of heading and flowering, the setting rate varied greatly, and the decreasing range of setting rate increased with the increase of total munber of grains. The abnormal high temperature of 38.0-41.0 ℃ occurred in the period of heading and flowering of single-season hybrid rice, and the setting rate decreased, resulting in a decrease of 28.8%-53.8% in yield. The decrease of yield of single-season hybrid rice due to abnormal high temperature during the period of heading and flowering resulted mainly from the decrease of setting rate.

Key words: hybrid rice, high temperature, heading and flowering, setting rate, yield