Response of eighteen rice (Oryza sativa L.) cultivars to temperature tested using two types of growth chambers

Genetic variation in the growth response to temperature is a basis for developing adaptation measures to global warming, but evaluation of cultivars for the temperature responses may depend on other environmental factors such as light. In this study, we tested the growth responses of 18 diverse rice cultivars to constant day/night temperature of 25, 28, 31 and 34°C in artificially-lit growth chambers (ALC) in Wagga Wagga (7.8 MJ m-2 d-1), and in naturally-lit chambers (NLC) in Yanco (25 and 28°C and 13.4 MJ m-2 d-1 31 and 34°C and 11.5 MJ m-2 d-1), both in NSW, Australia. There was a significant interaction between temperature and chamber type for total shoot and panicle biomass; total shoot biomass was largest at 31°C in ALC, and at 25 and 28°C in NLC. From the average of all temperatures, the total shoot biomass declined by 29.5% in plants grown in ALC compared with those grown in NLC. Importantly, cultivar performance in ALC was similar to that in NLC at these temperatures, as evidenced by the highly significant correlation in total shoot biomass between ALC and NLC. Among 18 cultivars, IR64, IR72, N22, Vandana, Takanari and Koshihikari commonly produced a larger total shoot biomass under higher temperature conditions. Leaf area at earlier measurement date was highly correlated with the final total shoot biomass at the higher temperature more than specific leaf area.