Chapter 4: Nutritionally Improved Sweetpotato

ABSTRACT:  Sweetpotato is grown in many developing countries, and varieties can be white‐, yellow‐, orange‐, red‐, or purple‐fleshed. This crop is a secondary staple food crop in parts of Eastern and Southern Africa, and an important component of animal feed in countries such as China. This case study describes and compares 2 nutritional improvements of sweetpotato. One improvement involves selecting and breeding orange‐fleshed sweetpotato as a biofortified crop to reduce vitamin A deficiency in Africa. The 2nd improvement aims to increase both the quality and quantity of protein in sweetpotato through the introduction of the synthetic asp‐1 gene (; ). Nutritional issues considered include the role of the sweetpotato in human nutrition, with a focus on Africa, and its potential to combat vitamin A deficiency and undernutrition; and its role in animal nutrition, specifically through increasing both the level and quality of protein. The protein case study concentrates on the event TA3 developed at Tuskegee Univ. (), which has been shown to have no negative agronomic characteristics. In terms of safety, the history of sweetpotato use and the measurement of a number of antinutrient compounds in this crop, such as oxalic acid, trypsin inhibitor, and furanoterpenoid compounds, are considered. If the orange‐fleshed sweetpotato are to be used in animal feed in a way not previously done, it is recommended that additional nutritional testing, such as for performance and bioavailability, be carried out in domestic animals. Four studies are recommended for the ASP‐1 sweetpotato. First, testing the safety of the genetic modification with the asp‐1 gene and derived ASP‐1 protein. Second, carrying out supplementary compositional studies focused on, for example, appropriate antinutrients, such as oxalic acid, trypsin inhibitor, and others where appro‐priate. Third, documenting the phenotypic properties of the sweetpotato line and its comparator grown in representative production sites. Fourth, measuring the performance of animals fed ASP‐1 sweetpotato compared with those fed conventional sweetpotato varieties. These studies could use a suitable animal model; an ILSI task force formulated guidelines for this type of study in a report titled Best Practices for the Conduct of Animal Studies to Evaluate Genetically Modified Crops (). Data on protein bioefficacy in the enhanced protein sweetpotato are available from 1 hamster study.