Screening and characterization of cultivar with M-type amylopectin in Japanese upland rice

Abstract

Asian rice (Oryza sativa L.) cultivars were recently classified into L-type, S-type, and intermediate M-type (rich, poor and middle intermediate-chain) on the basis of the fine structure of amylopectin in their grains. We selected 4 cultivars with M-type amylopectin from 174 local Japanese nonwaxy upland rice cultivars by scoring the disintegration of starch granules in alkaline solution and measuring the pasting temperature (PT) of their rice flours. Analyzed amylopectin fine structure, these cultivars exhibited intermediate characteristics between those of S-type Koshihikari and L-type IRAT109. Moreover, compared hardness of dumpling cakes after cooled for 3 h and 24 h. The hardness was in the order L-type > M-type > S-type, each other. On the other hand, the amylopectin chain ratio (ACR) was negatively correlated with the hardness of dumpling cakes both after cooled for 3 h and 24 h. Therefore, we concluded that the 4 cultivars—Chikanarijyun1, Hokkaiakage, Kairyo13, and Mogamichikanari1—had M-type amylopectin, and Japanese local upland rice has wide genetic diversity about starch mutation.