Breeding Vigna Unguiculata (L.) Walp. (cowpea) Lines Tolerant to the Phosphorus Poor Soils of Sub-Saharan West Africa.

Vigna unguiculata (L.) Walp. (cowpea) is a staple crop for countries across Sub-Saharan West Africa where its leaves, pods and seeds are consumed by both people and livestock. However, soils of West Africa are poor in phosphorus (P), a soil macronutrient all crops need for growth. The cost of using P reserves to produce fertilizer with P is too high for developing countries in Africa, and thus fertilizer with P is not readily available. The purpose of this research is to start breeding work for the development of cowpea lines that grow well in low P soils. A hydroponic phenotypic screening method was created to identify cowpea varieties that have measurable tolerance to growing in media deficient in P. Three cowpea varieties were identified with measurable tolerance as estimated by shoot biomass. Both tolerant and susceptible varieties from the screen were further studied by analyzing root biomass, internal shoot P content, and internal root P content. This further analysis gave basic physiological insight into cowpea varieties that are tolerant to P deficient media relative to varieties that are susceptible to P deficient media. Tolerant cowpea varieties were crossed with susceptible varieties and used to produce F₁, F₂, and BC₁ seed. The F₁, F₂ and BC₁ seed was also screened with the hydroponic method to determine the inheritance of the low P tolerance trait.