Breeding and Genetic Analysis of Tolerance to the Phosphorus Poor Soils of Sub-Saharan West Africa in Vigna Unguiculata (L.) Walp. (cowpea).

In the United States, two types of Vigna unguiculata (L.) Walp. (cowpea) are consumed as seed: black-eyed peas and purple hull peas. In Sub-Saharan Africa, cowpea is a widespread staple crop consumed for all components – leaves, pods, and seed – 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 and genetic work for the development of cowpea lines that grow well in low P soils. At least three cowpea varieties have been successfully identified with measurable tolerance as estimated by shoot biomass in a hydroponic screening method. Both tolerant and susceptible varieties have been further analyzed for seed P, root biomass, internal shoot P content, and internal root P content to gain basic physiological insight into cowpea varieties' tolerance to P deficiency. This research lays the foundation for determining genes or quantitative trait loci (QTL) responsible for cowpea's tolerance to low P soils. F₂, BC₁ and recombinant inbred line (RIL) populations have been developed from ‘high x low' crosses of lines for their tolerance to low P soils. F₂s and BC₁s have been screened for tolerance to understand the genetic control of the trait. The RILs will be used to begin QTL mapping using simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) markers. QTL mapping will give a potential foundation for future marker-assisted selection (MAS) of the low P tolerance trait in cowpea and other crops.