Masor, Laura Lee (2016-08). Molecular Mapping of Traits in Cowpea. Doctoral Dissertation.
Cowpea (Vigna unguiculata L. Walp) is a leguminous crop that many around the world rely on to meet their basic nutritional needs through the consumption of the protein and fiber rich grain and vegetative matter. Water and soil fertility stress affect this crop like many other crops; by reducing biomass and grain yield. Genotypes of cowpea have been identified that possess genes that confer tolerance to drought and resistance to interveinal chlorosis (IC) due to micronutrient deficiency. In order to map the quantitative trait loci (QTL) associated with these traits, a recombinant inbred line population (RIL) was created from the parental genotypes 'IT98K-476-8' and 'Golden Eye Cream' (GEC). This population was phenotyped for vegetative and yield traits and leaf chlorosis. The vegetative and yield data was used to calculate a drought susceptibility index (DSI) that was used in QTL mapping. The population was genotyped by restriction site-associated DNA sequencing (RAD-seq), and a linkage map spanning 1,084 cM was constructed from 4,154 single nucleotide polymorphisms (SNPs). Mapping for additive QTL identified 78 QTL that met a LOD threshold of three and 13 QTL that met the permuted LOD threshold for various traits and one DSI. Epistatic mapping resulted in 95 QTL involved in digenic interactions. From correlative statistics and co-localizations of QTL, it can be concluded that many of the traits mapped here are regulated by the same genes and that there are pleiotropic tradeoffs between some traits.