Molecular Breeding of Sweetpotato Carotenoids

Sweetpotato [sweet potato; Ipomoea batatas (L.) Lam.] is the seventh most valued food crop of the world. It has an inherent ability to grow under diverse agro-ecological and microclimatic zones ranging from tropical and subtropical zones to temperate areas with its tuberous roots enriched with the secondary metabolites of immense nutritional value. Among these, carotenoids are the most conspicuous one for having their use in nutritional, pharmaceutical, food, feed, aquaculture, and cosmetic industries. In food industries, carotenoids are used as food additives being antioxidants with attractive colors. Despite the immense economic importance, sweetpotato has received lesser attention in terms of its breeding with improved varieties. The conventional method of breeding by crossing has not been much successful due to the complexity of genome sterility and cross-incompatibility. Hence, the modern molecular breeding approaches, e.g. genetic, genomic, and metabolic (pathway) engineering, have been applied to this crop by some of researchers in Japan, Korea, and China to generate various cultivars with improved quantities and qualities of carotenoids. This has also opened a new gate for molecular breeders to engineer new sweetpotato cultivars enriched with carotenoids under current global scenario of dramatically rising climatic changes where novel food resources are bitterly needed, especially under alarmingly growing world population, the majority of which suffers from malnutrition

Effect of Growth Stages on Anthocyanins and Polyphenols in the Root System of Sweet Potato

The storage roots of purple-fleshed sweet potato contain a variety of anthocyanins and polyphenols. Little is known about changes in the total content and composition of anthocyanins and polyphenols in the early growth stages of the root system. In this study, we investigated the changes in anthocyanins and polyphenols in the root system of purple-fleshed sweet potato cultivars at 15, 30, 45, and 60 days after transplant (DAT). Unexpectedly, the highest percentage of acylated anthocyanins in three purple-fleshed cultivars among all growth stages was at 15 DAT. On the other hand, the total polyphenol content in the early growth stages of the root system increased rapidly toward 45 DAT, just before the beginning of storage root enlargement, and then decreased rapidly as the storage roots began to enlarge. These data indicate that the early growth stage of the root system is a critical time. This timing may present a strategy to maximize the accumulation of polyphenols with high antioxidant activity, as well as acylated anthocyanins, to protect against abiotic and biotic stresses