Mutation Breeding of African Nightshade ( Solanum section Solanum )

African nightshades ( Solanum nigrum- related species) are some of the most widely consumed traditional leafy herbs and vegetables, particularly in Africa and South-East Asia. The leaves contain high levels of vitamins (especially A, B and C), mineral fibres (such as iron, calcium and phosphorus), carbohydrates and proteins. They also contain phenolics and alkaloids, such as nicotine, quinine, cocaine, and morphine, which are known for their medicinal attributes. With the realization of their high nutritional, medicinal and health benefits, the demand for these vegetables has been on a rapid and steady rise in the recent years. However, due to very low leaf yields that are considered uneconomical compared to other high-yielding and high-value horticultural crops, production of these vegetables remains on a small scale. Prolific early flowering and excessive fruit- and seed-set, which compete with leaf production, are the main limiting factors on leaf yields. To eliminate or reduce fruit-set, hence competition with leaves, induction of male-sterility is probably one of the most immediate options. The main challenge that faces this strategy is propagation and maintenance of male-sterile lines. This review focuses on the mutation breeding for improved leaf yields of African nightshades with special reference to male-sterility. Aspects of propagation and maintenance of male-sterile lines are discussed.