Effects of high temperature stress at heading stage on pollination and fertilization of different types of rice variety

Abstract

High temperature stress at heading stage is one of the important natural disasters causing the reduction of the seed setting rate of rice in the middle-lower reaches of Yangtze River. This study investigated the effects of high temperature stress at heading stage on fertilization rate of modern rice varieties and combinations, including modern inbred japonica, three-line hybrid indica rice and two-line hybrid indica rice cultivars under the field condition. The modern inbred japonica cultivar showed better high temperature tolerance at heading stage, while the hybrid rice, especially the two-line hybrid indica rice cultivar, was susceptible to high temperature at heading stage, and their fertilization rate was close to zero under 39°C at heading stage. Shanyou 63 showed well tolerance to moderate high temperature stress, which was decreased rapidly under the severely high temperature. The high temperature tolerance showed the great differences among cultivars under the same treatment. The pollen numbers per anther in the two tested super two-line hybrid rice was the highest, which was more than 1750. Ningjing 1 had the lowest pollen number, which was only 979.8 per anther. In general, the pollen number per anther in hybrid rice was higher than that in inbred rice, and that in indica higher than that in japonica. The correlation of pollen number per anther was not significant with high temperature tolerance. High temperature stress decreased the anther dehiscence coefficient significantly. Ningjing 1 could maintain certain extent of longitudinal fracture rate under the severely high temperature stress, and more pollen quantity on stigma after anthesis. The results indicated that high temperature tolerance at heading stage is not related with pollen production, but has close relationship with anther dehiscence and pollen quantity on stigma.