Growth and Grain Yield Diversity for High Temperature Tolerance in Rice Cultivars.

Temperature is one of key abiotic stress factors affecting life on Earth. Most plants, being non-locomotive, developed a variety of overlapping but distinct responses to elevated temperatures that minimize damage to cellular organelles and functions. To fulfill our objectives, an experiment was conducted in state-of-the-art sunlit plant growth chambers known as Soil-Plant-Atmosphere-Research units designed to provide quantitative data using 21 cultivars that are grown in Mississippi Delta. The cultivars grown in pots under optimum water and nutrient and in an outdoor environmental condition were transferred to SPAR chambers prior to panicle initiation. The day/night temperature treatments of 82/68°F (optimum), 90/75°F (moderately high), and 97/82°F (high) were imposed until grain maturity. We found there are significant differences in total biomass, physiological parameters, grain-fill percentage, and filled grain weight and numbers among the cultivars in response to moderately high and high temperatures. 

We found CLXL 745 showed greater potential and relatively higher tolerance to heat compared cultivars such as REX which is moderately heat tolerant and Bowman which is heat sensitive among the cultivars studied.  The relative scores along with cultivar-specific yield potential in a given region will be useful for rice producers to select cultivars for a niche environment and planting date.