Increasing demand for bioproducts and rising interest in the development of alternative crops to promote farm diversification have stimulated research on alternative feedstocks for production of starches, sugars, and other natural plant-derived products (Harwood et al., 1999; Henry, 2010). Sweetpotatoes with higher starch content may allow farmers to produce sweetpotatoes for industrial starch production, which can be used directly in the food and paper industries or to produce a number of biobased chemicals including biofuels and plastic precursor molecules (Ellis et al., 1998; Werpy and Petersen, 2004), thus opening new markets. Sweetpotatoes may also have potential as a source of anthocyanins for use as a natural food colorant and functional food ingredients because of their recognized antioxidant and anticancer properties (Philpott et al., 2004; Teow et al., 2007). In some regions of the world, purple-fleshed sweetpotatoes are commonly consumed in a variety of forms (e.g., boiled, baked, and mashed), while in others, notably Japan and China, purple-fleshed cultivars are also used as a source of industrial anthocyanins (Suda et al., 2003).
Interest in sweetpotato anthocyanins for industrial food colorants and antioxidant additives is rising as demands for natural products and health foods increase (Shahidi, 2000). Purple-fleshed sweetpotatoes have significant untapped potential as a source of cyanidin and peonidin (Odake et al., 1992). The anthocyanins from purple-fleshed sweetpotatoes have shown significant antioxidant activity, which is associated with anticancer and other health promoting properties (Teow et al., 2007). To develop this potential market in the United States, we are developing purple-fleshed cultivars adapted to local growing conditions. Since few purple-fleshed cultivars have been introduced to the United States, purple-fleshed lines have been crossed with a broad range of germplasm (orange, white, and purple clones) with offspring being selected for adaptation to the southeastern United States and high concentrations of anthocyanins. As part of this breeding effort, the inheritance of TMA concentration in the populations was studied.
Sweetpotatoes may be suitable as an industrial bioproduct feedstock because they can be grown on marginal soils with lower inputs of fertilizer and pesticides than other crops, thus reducing competition with food and feed crops and reducing the need for chemical inputs that require fossil fuels in their production (Woolfe, 1992). Increased farm diversity reduces risk over specialized farms because at times when one commodity has lower prices, another may have higher prices. However, a grower’s decision to diversify is impacted by additional factors including management knowledge, required capital investments, and availability of suitable crops and/or livestock (Harwood et al., 1999).
Development of regionally adapted, high-starch and/or purple-fleshed sweetpotato may allow development of new sweetpotato-based industries in North Carolina and the southeastern United States. In response to the rising needs for feedstocks and crop diversification, intensive breeding efforts to increase biomass and anthocyanin production from sweetpotato have begun. To date, most sweetpotato breeding efforts in the United States have focused on development of orange-fleshed, low dry-matter, tablestock cultivars. As a result, little information is available for critical bioproduct production traits such as DM, starch content, total fresh yield, and anthocyanin levels. To further understand the genetic basis of these important traits for bioproduct production, an NCII mating design (i.e., a factorial crossing block in which a set of females is crossed in all possible combinations to an independent set of males) (Comstock and Robinson, 1948) experiment was undertaken to identify combining abilities and genetic variances underlying these traits.
This paper describes an NCII breeding experiment to identify combining abilities of potential sweetpotato parents for DM and anthocyanin production. These two components may allow development of new sweetpotato processing industries in the southeastern United States. DM content is closely correlated with starch content (Hall and Smittle, 1983), and the relative ease of measuring DM content has allowed breeders to use it as an estimate of relative starch content. While many purple-fleshed cultivars have low anthocyanin concentrations and/or are unadapted to North Carolina, breeding efforts are showing that adapted cultivars with high anthocyanin concentrations can be developed.
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