Influence of environmental temperature during the ripening period on the amylose content and whiteness of low-amylose rice

Abstract

We examined the effects of environmental temperature (ET) during the ripening period on the amylose content and the whiteness values (an indicator of dull endosperm), in seven low-amylose rice cultivars. ET showed a significant negative correlation with the amylose content in all cultivars examined. ET-dependent variation in amylose content was larger in low -amylose rice cultivars than in Koshihikari and Nipponbare. Ir was difficult to find any correlation between the variation in the amylose content and the variation in ET or 1,000-grain weight. We considered that the large variation in amylose content was attributable to the expression of the du gene, which was responsible for lowering the amylose content, and was markedly affected by the ET, except for Snow pearl. On the other hand, ET showed a significant positive correlation with the whiteness value. Low-amylose rice cultivars tested could be divided into two groups; One had a dull endosperm independent of ET ; and the other produced a dull endosperm depending on ET. The amylose content showed a significant negative correlation with whiteness value. The amylose content and the whiteness values varied with the cultivar more widely than with ET, suggesting that the amylose content and whiteness value of low-amylose rice cultivers are more affected by the genetic background than by ET.