[Correlation of intersubspecific hybrid rice spikelet fertilization rate with temperature and related statistic...

Using four types of rice, i. e., indica-japonica hybrid, intermediate hybrid, indica and japonica cultivars as test materials, this paper studied the sensitivity of intersubspecific hybrid rice to climatic factors, and the correlations between spikelet fertilization rate (SFR) and daily meteorological factors during 2000 and 2001. The results showed that the SFR of intersubspecific hybrids was lower than that of indica and japonica cultivars. Among eleven meteorological factors, temperature was the key factor, and the mean temperature within five or seven days around panicle flower blooming affected the SFR significantly. A comprehensive model of SFR-temperature was established, with which, the fittest temperature and safe temperature for fertilization of intersubspecific hybrids was estimated to be 28.2 - 29.3 degrees C and 23.4 - 24.3 degrees C, 2.2 degrees C and 1.5 degrees C higher than those of indica and japonica cultivars, respectively. It was suggested that the safe heading date for planting intersubspecific hybrid should be moved up to the last ten-day of September to the first ten-day of October in southern China, the first ten-day of September in middle and lower reaches of Yangtze River Valley, and the last ten-day of August to the first ten-day of September in rice planting area between Yangtze and Huai River.