RICE QUALITY AND PROCESSING Differential Grain Development and Endosperm Gene Expression as Tools to Understand Rice Cultivar Responses to Increased Nighttime Air Temperatures

Mounting evidence has made it clear that increasing nighttime air temperatures contribute to decreased head rice yields and decreased grain quality due to chalkiness and altered physicochemical properties. Our goal is to determine some of the fundamental changes that occur in developing rice kernels as they respond to high air temperatures, especially at night. Panicles collected from field-grown plants of six cultivars at growth stages R6, R7, and R8 show that as the overall reproductive growth stage progresses, there are a larger proportion of kernels at filling stages. We used rice gene chips to examine the total gene expression profiles of Cypress and LaGrue endosperm treated at high (30 °C) and low (18 °C) nighttime temperatures. We observed substantial differences in accumulation of some gene transcripts when comparing samples across the two cultivars, at either temperature. However, we observed fewer differences in gene expression when comparing tissues within a cultivar when plants were treated at the two different nighttime temperatures.