Genotypic Variation in Rice Cold Tolerance Responses during Reproductive Growth as a Function of Water Temperature during Vegetative Growth

Abstract

We examined genotypic variation in the effect of rice (Oryza sativa L.) responses to water temperature (Tw) during vegetative growth on cold tolerance during reproductive growth in pot and field experiments. Cold tolerance was evaluated based on the percentage spikelet sterility induced by a cool and deep irrigation treatment during the reproductive growth phases. In the pot experiment, rice plants from two cultivars with different cold tolerance were exposed to different levels of Tw during vegetative growth and their cold tolerance was tested. Spikelet sterility of both cultivars decreased with increasing Tw during the vegetative growth phase for temperatures ranging from 19 to 30°C, with parallel lines for the regression equations for sterility as a function of temperature (a slope of 4.0% per 1°C) for both cultivars, although the y‐intercepts differed by 38% points between the cultivars. In the field experiment, four rice cultivars were grown under two levels of Tw during vegetative growth, and their cold tolerance was tested during reproductive growth at two locations (Miyagi Prefecture and Aomori Prefecture in Japan). We found that spikelet sterility decreased at high Tw during vegetative growth for all cultivars and locations. Our results suggest that high Tw during vegetative growth can improve cold tolerance during reproductive growth for the tested cultivars without a significant cultivar × Tw interaction.