The Anther Color as an Indicator of Heat-Induced Spikelet Sterility in Rice

Heat-induced spikelet sterility of rice is a serious concern in food production under global warming. During the normal anther dehiscence, mature anthers turn to white after pollen release, whereas some anthers with the numerous hydrating pollen grains left inside the anther tissues under heat conditions, turn to yellow. In this study, our hypothesis that the ratio of spikelets with those anthers might be used as an indicator for visually evaluating heat tolerance at flowering was tested. Eleven rice cultivars were used to treat heat conditions. The results show that spikelet fertility, the pollen grain number on the stigma, pollen germination ratio in the cultivars with spikelets with white anthers were greater than those with yellow anthers in each cultivar. The fertility of spikelets exhibiting the yellow anthers in some cultivars, such as N22 and XM5, was shown to be higher than those with white anthers in other cultivars. In addition, a stepwise linear regression suggests that the color of anthers indicated as the consequence of pollination status might be associated with the spikelet fertility. And hence, it is concluded that the anther color objectively evaluable would be used as a rapid, straightforward, and useful indicator associated with spikelet sterility.