Studies on the breeding for improving starch properties in sweet potato

To develop new uses for sweet potato starch, we studied about breeding for improving starch properties in sweet potato. The amylose content of the germplasm collections of sweet potato ranged from 11.2 to 15.3%. There were varietal and geographical differences in the amylose content of sweet potato. Analysis of the varietal and annual variations in starch properties suggested that selection for pasting temperature, setback and amylose content can be effective. The variations of amylose content in sweet potato and its related diploid wild species could be increased by crossing and mutagenesis, and variants with a low/high amylose content could be selected. Furthermore, a new sweet potato cultivar "Quick Sweet" was developed, featuring low gelatinization temperatures and altered starch fine structure. Gelatinization temperatures and pasting temperatures of Quick Sweet starch were approximately 20 degrees C lower than those of ordinary sweet potato cultivars. The chain-length distribution of amylopectin showed that Quick Sweet starch had a higher proportion of short chains (DP6-11) than the ordinary cultivars. Starch retrogradation, evaluated by leaked water percentage and hardness of starch gels after cold storage, indicated that Quick Sweet starch had excellent cold storage stability.