Determination of quality traits, and the nutrient and mineral contents of cowpea varieties in South Africa

Abstract

Eastern Cape, followed by Limpopo, have the highest numbers of citizens experiencing food insecurity. The Limpopo and Free State provinces share the highest prevalence rate of children affected by iron deficiency anaemia leading to severe stunting and underweight. Cowpea is an important grain legume that is rich in proteins (20-24%), minerals and vitamins for human and animal nutrition. Cowpea stands to enhance food security and nutrition in rural South African communities. Introduction of cowpea varieties that are rich in proteins, minerals and vitamins will improve the quality of the dietary intakes and nutritional status of the poor. To fast-track the development of improved cowpea varieties that meet the nutritional needs of consumers and farmers, thirty cowpea improved varieties were introduced and evaluated to determine their qualities and the nutrients they contain. This will assist breeders in ascertaining their usefulness and how to deploy the traits in breeding programmes. The seeds were harvested from seed multiplication plots during 2017 growing season, and were analysed in three replications to determine their nutrient and mineral contents (crude protein or CP, Ca, Na, Mg, Fe, Cu, Zn, P, K and moisture). The mineral contents were determined using an atomic absorption spectrophotometer while CP content was determined by the Kjeldahl method using Kjeltec™ Model 2300, as described in Foss Analytical AB manual. Results showed that the varieties exhibited significant (P<0.05) variations for the nutrients and minerals determined except for P and moisture. Eight varieties out-performed the two local control varieties (Glenda and Bechuana White with 24% and 20% respectively) in CP with a range of 25-31%. Many varieties also significantly out-performed the local checks in respect of minerals tested: 4, 12, 6, 5, 14, and 15 varieties exhibited higher concentrations of Ca, Mg, Na, Zn, Cu and Fe, respectively. Results also show that the quality of grains varied in terms of seed colour, texture, and eye colour. The results not only demonstrate that many of the improved varieties were better than the control varieties, but have also provided a database for utilising the promising varieties in breeding programme for the development of new cowpea germplasm with better quality traits and nutrient contents. Variation in seed qualities offers opportunities for farmers and consumers to make choice as these quality traits influence acceptability and marketability of cowpea in South Africa. Key words: Bechuana White, bio-fortification, dietary intake, food security, marketability nutrition, protein content, Vigna unguiculata