Factors determining the occurrence of floret sterility in rice in a hot and low-wind paddy field in Jianghan Basin, China

Abstract

• High temperature (<36.5 °C) and low wind induced floret sterility in the paddy field. • High temperatures increased the sterility through processes after pollen germination. • Wind lessened the sterility through stable pollination and probably via cooling. • Positive effects of low and erect panicle, and short anther were newly demonstrated. • Positive effects of long basal anther dehiscence and early flowering were confirmed. Global warming may increase the occurrence of heat-induced floret sterility (HIFS) in rice. The effects of meteorological factors and plant traits on the occurrence of floret sterility have only been examined independently and under controlled or simplified conditions. The aim of this study was to comprehensively clarify the role and impact of these factors in HIFS in rice under practical field conditions. We observed pollination and seed set of 12 rice cultivars with wide variation in traits potentially related to HIFS for 3 years in a paddy field in the Yangtze Valley in China where HIFS sometimes occurs. Floret sterility increased as temperature increased under moderately high temperatures (32–36.5 °C) and low-wind conditions (<3.5 m s −1 at flowering time). Path analysis with multiple regression revealed that high temperatures increased the occurrence of floret sterility through processes after pollen germination on the stigma and that wind lessened the occurrence of floret sterility; the magnitude of the wind effect was equivalent to that of high temperature. Multiple regression analysis estimated that low and erect panicles, and short anthers have positive effects on tolerance to HIFS and known heat tolerance traits, e.g., long anther dehiscence at the base of the anther and early morning flowering. The results clarified the factors that control HIFS in the paddy field and identify the processes and traits that scientists and breeders should focus on to mitigate HIFS under global warming.