Analysis of genotypic and environmental effects on rice starch. 1. Apparent amylose content, pasting viscosity, and gel texture.

Eight rice varieties with wide diversity in apparent amylose content (AC) were selected and planted in the early season and late season of Hangzhou and in the winter season of Hainan for two consecutive years to study the genotype x environment effects on the starch properties of the grain. Analyses of variance showed that AC, cool paste viscosity, breakdown viscosity, setback viscosity, peak time, gel hardness, adhesiveness, and cohesiveness were mainly affected by genotypic variation, whereas peak viscosity and hot paste viscosity were mainly affected by environmental variation. The year x season, year x variety, seasonx variety, and year x season x variety effects were significant for most traits, indicating significant genotype x environment interactions. AC was significantly correlated with all other parameters except PV. Because the Wx gene controls the synthesis of amylose in rice, the mechanism of how the environment affects starch properties is discussed in relation to Wx expression and regulation. The implications of the results for rice breeders and starch-based food manufacturers are discussed.