High temperature susceptibility of sexual reproduction in crop plants

Climate change-induced increases in the frequency of extreme weather events, particularly heatwaves, are a serious threat to crop productivity. The productivity of grain crops is dependent on the success of sexual reproduction, which is very sensitive to heat stress. Male gametophyte development has been identified as the most heat-vulnerable stage. This review outlines the susceptibility of the various stages of sexual reproduction in flowering plants from the time of floral transition to double fertilization. We summarize current knowledge concerning the molecular mechanisms underpinning the heat stress-induced aberrations and abnormalities at flowering, male reproductive development, female reproductive development, and fertilization. We highlight the stage-specific bottlenecks in sexual reproduction, which regulate seed set and final yields under high-temperature conditions, together with the outstanding research questions concerning genotypic and species-specific differences in thermotolerance observed in crops. This knowledge is essential for trait selection and genetic modification strategies for the development of heat-tolerant genotypes and high-temperature-resilient crops.