Effects of cross combination on the total content and its composition of anthocyanins in sweetpotato (Ipomoea batatas L.)

Anthocyanins in sweetpotato (Ipomoea batatas L.) have attracted much attention in light of their multiple health benefits and excellent properties as processed foods. Although crossbreeding is an effective way to breed new cultivars of sweetpotato, there are few reports on how anthocyanin content and composition are passed on to F₁ hybrid generations by crossbreeding because of a complex genome and self-incompatibility reactions. In this study, three purple-fleshed sweetpotao cultivars, ‘Akemurasaki’, ‘Kyushu No.137’, ‘Purple Sweet Lord’, and one yellow-fleshed cultivars, ‘HE306’ (Silk Sweet®) selected for their anthocyanin contents and compositions were crossed in six combinations. Flowering was induced by using a sweetpotato grafting technique to obtain a total of 143 F₁ hybrid lines. Anthocyanin content, the percentage of acylated anthocyanins, and the peonidin/cyanidin ratio in each of these F₁ hybrid lines were investigated. In the F₁ hybrid generations derived from these six cross combinations, many lines tended to have anthocyanin contents similar to those of the parent cultivars. In particular, among the 36 hybrid lines derived from crosses between ‘Akemurasaki’ and ‘HE306’ (Silk Sweet®), 13 lines with high anthocyanin contents (≧200 mg·100 g FW⁻¹) and 20 lines without anthocyanins were identified. The F₁ hybrid lines of this combination had anthocyanin contents similar to those of the parent cultivars, with anthocyanin-free lines appearing more frequently than anthocyanin-containing lines. Interestingly, we also identified a line with an extremely low percentage of acylated anthocyanins (49.7%) from the F₁ hybrid lines derived from a cross between ‘Purple Sweet Lord’ (seed parent) and ‘Kyushu No. 137’ (pollen parent). Moreover, the F₁ hybrid lines derived from crosses between ‘Purple Sweet Lord’ and ‘Kyushu No.137’ tended to have high peonidin/cyanidin ratios. This study provides an example of the inheritance of anthocyanin content and its composition in sweetpotato, which supplies valuable information for selection of parents to breed purple-fleshed cultivars.