Analysis of Physiological and Biochemical Characteristics of Six Mutants with Stable High Percentage of Chalkiness in Rice Grains

Abstract

Chalkiness is an important quality character in rice,which is affected by comprehensive effects of genetic and environmental factors.Furthermore,the environmental factors affect the formation of chalkiness through the physiological and biochemical processes.Here,we screened six mutants with stable severe chalky rice grains from the T-DNA insertion mutant pool of cultivar Nipponbare.The changes in activities of the key enzymes associated with starch synthesis,including sucrose synthase,adenosine diphosphoglucose pyrophosphorylase (AGPase),starch synthase,starch branching enzyme and starch debranching enzyme in grains during the filling period,could impact the starch synthesis,the shape and fine structure of the starch granule,thus result in the formation of chalkiness.Temperature condition during grain filling is one of the most important environmental factors affecting the quality of rice.But high temperature stress did not take place during this experiment.To explain the mechanism of the formation of chalkiness from the physiological and biochemical aspects,we analyzed the fluctuation of the key enzyme activities associated with starch synthesis,sucrose content,starch content,and the ratio of amylose to total starch in mature grains.The results suggest that physiological studies of grain development are essential to reveal the formative mechanism of chalky rice.