Evaluation and use of physicochemical properties as index traits for selecting rice cultivars with extremely high palatability

Abstract

In order to evaluate the usefulness of several physicochemical properties for selecting rice cultivars with high palatability, we analyzed the relationship between the palatability and the physicochemical properties using 20 japonica rice cultivars from 1998 to 2002. By cluster analysis the 20 cultivars were classified into four groups besed on their palatability score for five years. We examined the relationship between the palatability score and physicochemical properties of the mixture of all four groups. The amylose content, protein content, maximum viscosity, breakdown, and textural characteristics (H/-H : hardness / adhesion ratio, H/A3 : hardness / adhesiveness ratio), showed a significant correlation with palatability score. We examined the palatability score of rice strains that were recently developed in Fukuoka Agricultural Research Center, and found that the number of the cultivars with extremely lower palatability than Koshihikari (group 4), has been decreasing year by year. Then, we analyzed the relationship between the palatability score and physicochemical properties of the mixture of group 1, 2 and 3, which showed a relatively higher palatability than group 4. Only amylose content and textural characteristics (H/-H, H/A3) showed a significant correlation with the palatability. We compared the amylose content and textural characteristics among the four groups. The difference in amylose content among these three groups were not significant. However, a significant difference of H/-H was detected between group 2, which has better palatability than Koshihikari, and group 3, which has slightly lower palatability than Koshihikari. Therefore, textural characteristics could serve as useful index traits for developing rice cultivars with extremely high palatability in the breeding programs.