Analysis of genotypic diversity in starch thermal and retrogradation properties in nonwaxy rice

Abstract

A total of 236 nonwaxy rice including 56 landraces (landrace set) obtained from the germplasm center and 180 cultivars and breeding lines (breeding line set) obtained from various breeding programs were studied for the genetic diversity of flour thermal and retrogradation properties, focusing on comparison of the differences between the landrace set and breeding line set. Wide diversity was found in all flour physicochemical properties, e.g. peak temperature ( T p) ranged from 63.2 to 79.8 °C, width at half peak height (Δ T 1/2) of gelatinization ranged from 4.7 to 10.5 °C; enthalpy of gelatinization (Δ H g) ranged from 5.6 to 11.4 J/g, and retrogradation percentage ( R%) ranged from 0.2% to 54.2%. The breeding line set had a larger range of thermal properties and R% than in the landrace set, whereas the range of retrogradation enthalpy was similar between two sets. The mean for all parameters differed between the two sets; mean Δ T 1/2 of the landrace set was smaller than in the breeding line set, whereas other parameters were larger in the landrace set than the breeding line set. Correlation analysis showed that apparent amylose content was positively correlated with Δ H g ( r = 0.65, P < 0.001) and R% ( r = 0.68, P < 0.001), and negatively correlated with Δ T 1/2 ( r = −0.28, P < 0.001). All thermal and retrogradation properties themselves were correlated; the correlation between Δ T 1/2 and all other parameters was negative, whereas all other pairs were positive.