Resistant starch and starch thermal characteristics in exotic corn lines grown in temperate and tropical environments.

摘要

Corn as a food that is heated and cooled to allow starch retrogradation has higher levels of resistant starch (RS). Increasing the amount of RS can make corn an even healthier food and may be accomplished by breeding and selection, especially by using exotic germplasm. 60 breeding lines of introgressed exotic germplasm backgrounds, selected for high yield, were grown in 3 tropical and temperate locations and analysed for starch thermal characteristics and RS levels. Although actual values for all starch characteristics were within normal levels, most characteristics had significant genotypic effects, and all had significant location effects. Thermal properties of retrograded starch were more influenced by the environment than the thermal properties of raw starch, making retrograded starch traits more heritable than raw starch traits. This suggested that a breeding strategy based on retrograded starch traits will have a better chance of success than a breeding strategy based on raw starch traits. A significant genotype effect for RS levels indicated that genotypic selection to raise the level of RS and increase the healthful aspects of corn food should be successful. Significant location effects indicated that breeders using winter nurseries to accelerate their breeding progress need to be careful when making selections using RS data collected on seed grown in the tropics. A small but highly significant correlation between RS and some thermal characteristics, especially percentage of retrogradation, indicated that it may be possible to select promising genotypes for RS selection based on the extensive database of thermal characteristics collected on a wide number of diverse corn lines.