Effects of high air temperature on rice grain quality and yield under field condition

Abstract

High air temperature (HAT) limits grain yield and quality in rice (Oryza sativa L.). Th is study was conducted to determine the eff ects of HAT from R3 (panicle exertion from boot) to R8 stage (physiological maturity) on rice grain yield and quality (milling, appearance, cooking and eating, and nutrition qualities). A split-spot experiment based on randomized complete design was performed, involving two cultivars (japonica Koshihikari and indica IR72), two temperature treatments, and three replicates. Rice cultivars as main plot treatments were grown in a paddy fi eld. Th e HAT and natural air temperature (NAT) treatments were regarded as subplot. Percentage of chalky kernel increased, whereas head rice yield, amylose and starch contents, and grain yield decreased in both cultivars under HAT, when compared with those under NAT. Th e HAT enhanced values of peak viscosity and breakdown, but decreased value of setback for Koshihikari. Conversely, starch viscosity characteristics for IR72 were unaff ected by HAT. Relative content of amino acids in grains were enhanced; however, absolute content of some amino acids did not increase due to the reduction of grain weight under HAT. Th e HAT also increased absolute content of grain protein in IR72, but not in Koshihikari. Th e present study indicates that HAT decreased rice milling, appearance qualities and grain yield, while it positively infl uenced not only cooking and eating qualities in Koshihikari but also some nutritional components of grains in both cultivars. © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.