Effect of Temperature at Different Durations after Anthesis on Rice Quality and Variations between Positions on a Panicle

Abstract

The aim of this study was to investigate the effect of high temperatures imposed at early and mid grain filling stages on the quality of grains at different positions on a panicle,and to seek cultivation techniques to improve rice quality.Two rice cultivars,Yangdao 6(indica)and Yangjing 9538(japonica),were pot-grown and subjected to high(35℃)temperatures during the initial(0-10 d)and mid(10-20 d)grain filling stages after anthesis.Compared with atmospheric temperature(25-27℃,CK),the high temperature treatments significantly affected grain quality.Generally,the influence of the temperature treatment at the initial filling stage was more than that at the mid filling stage,however,the grain quality varied with cultivars and grains positions.High temperatures imposed at early and mid grain filling stages reduced,head rice rate(HRR),head milled rice rate(HMRR),but increased crude protein content(CPC),and the grains on primary branches were affected more than those on secondary branches,and later-flowered grains were affected more than early-flowered grains.High temperature imposed at the early grain filling stage significantly increased chalkiness degree(CD)and chalky grain percentage(CGP)of early-flowered grains at the same branch;high temperature treatments imposed at the early grain filling stage decreased amylose content(AC),and grains on primary branches were affected more than those on secondary branches.Sensitive of grain quality to temperature varied with cultivars and treatment times after anthesis.The influence of temperature on rice quality was more at the early grain filling than at the mid filling stage.Some cultural practices,such as balanced fertilization,arrangement of sowing date,and precise irrigation,would alleviate the influence of high temperature on rice quality.