Impact of high temperature on pollen germination and spikelet sterility in rice: comparison between basmati and non-basmati varieties

Increased temperature due to global warming may reduce pollen germination and induce spikelet sterility in rice crops. Anthesis is the most sensitive stage in rice and exposure to high temperature during this period may cause reduction in floral reproduction. Increased temperature will have different effects on different rice varieties. In the present study the effect of high temperature on pollen as well as on spikelet sterility in basmati (aromatic) and non-basmati (non-aromatic) rice varieties was quantified. Rice varieties were grown at 11 different sowing dates, to see the effect of varying temperature on pollen and spikelet sterility. Rise in temperature increased pollen sterility and reduced germination of pollen grains on the stigma. Temperature above 33°C during anthesis gradually increased pollen sterility in all rice cultivars. At 35.5°C, variety Pusa Sugandh 2 (basmati) recorded a pollen sterility of 17% and 26% reduction in pollen germination. The principal cause of sterility was reduced anther dehiscence and less pollen deposition on the stigma at higher temperature. Increased temperature during the grain-filling period also increased spikelet sterility in rice and variety Pusa Sugandh 2 was most affected. Non-basmati rice varieties were less affected by increased temperature than basmati types. The study indicated that increasing temperature could limit rice yield by affecting pollen germination and grain formation. It also suggested that sensitivity of pollen grains to temperature damage could be taken as one of the most important parameters for predicting rice yield in warmer climates