Carbohydrate components in sweetpotato storage roots: their diversities and genetic improvement

Abstract

Carbohydrates are important components in sweetpotatoes in terms of both their industrial use and eating quality. Although there has been a narrow range of diversity in the properties of sweetpotato starch, unique varieties and experimental lines with different starch traits have been produced recently both by conventional breeding and genetic engineering. The diversity in maltose content, free sugar composition and textural properties in sweetpotato cultivars is also important for their eating quality and processing of storage roots. In this review, we summarize the current status of research on and breeding for these important traits and discuss the future prospects for research in this area.

Keywords: Ipomoea batatas; carbohydrate; free sugar; maltose; starch; sweetpotato; texture.

Fig. 1

Optical microphotographs of Konahomare (KH) and Konamizuki (KM) starch granules (Kitahara et al. 2014). Bars in the photographs represent 50 μm.

Fig. 2

Weight-based chain-length distributions determined by gel permeation chromatography with refractive index detection and their calculated number-based chain-length distributions of Konahomare (KH) and Konamizuki (KM) amylopectins (Kitahara et al. 2014). The solid line indicates the distribution of weight-based chain lengths, and the dotted line indicates the distribution of number-based chain lengths. Vertical dotted lines indicate the division of the distribution into unit-chain fractions of the cluster structure of amylopectin. Commercial pullulan standards (closed circle) with known DPs were used for the column system.

Fig. 3

Inheritance of the amylose-free character of storage roots of transgenic sweetpotatoes by sexual crossing (Otani et al. 2007). C: non-transgenic Kokei 14’ plant, GR-1: transgenic amylose-free plant line with dsRNA of IbGBSSI. 1–4: progenies of GR-1 crossed with cv. ‘Chikei 682-11’.