Genetic linkage maps provide a genomic framework for quantitative trait loci identification applied in marker assisted selection breeding in crops with limited resources. It serves as a powerful tool to breeders for analysing the mode of inheritance of genes of interest and monitoring of the transmission of target genes from parents to progeny. Single nucleotide polymorphism (SNP) markers have a great influence on mapping research studies: for faster development of new varieties of crops due to its abundance and high number of polymorphism. Thus, this research work aimed at constructing genetic linkage map of cowpea using SNP markers. This will facilitate development of new varieties of cowpea. Single seed descent method of breeding was used to generate mapping population between IT-95K-193-12 and Ife-Brown. Fresh leaves from both parental lines and F1 hybrids were genotyped with 135 SNP markers. Data from125 polymorphic SNP markers were used to construct linkage map. Results revealed 12 linkage maps with an average of 10 markers to a chromosome and average marker distance of 3.02 cM between the markers. Constructed map provides basic information that could assist in genetic improvement of cowpea, most especially in developing brown blotch resistant cowpea varieties through detection of quantitative trait loci (QTL) responsible for brown blotch resistance in cowpea when utilizing marker assisted selection method.

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The experiment was conducted to characterize cowpea (Vigna unguiculata (L.) genotypes based on morphological characters. The experiment was carried out at the screen house of the Institute of Agricultural Research and Training (IAR&T), Moor Plantation, Ibadan in 2015 and 2016 using nine (9) cowpea varieties. Soil was sieved with 2mm sieved and sterilized. The experiment was laid out in Completely Randomized Design (CRD) with four replicates. Morphological data were collected based on descriptor for cowpea (IBPGR, 1983). For quantitative traits, analysis of variance revealed that genotype and years effect mean squares from pooled data were highly significantly different for days to first and 50% flowering (P ˂ 0.01), interaction between genotype and years effect also had significant effect on days to first and days to 50% flowering (P ˂ 0.05).Higher significant values were obtained for terminal leaf width, pod weight, pod length, days to physiological maturity, total seed weight per plant, 100 seed weight and number of seed per plant in 2015 than the year 2016. However there were no significant differences obtained for terminal leaf length, pod per peduncle, number of pod per plant, seed length, seed width, seed thickness, and number of seed per pod in both years. Qualitative characters results show thatgenotypic effect, year effect and their interactions were not significant for plant vigour. Modupe, Ife 98-12, Oloyin-Pelebe, Ife BPC, Oloyin-Nla and Sokoto genotypes had intermediate twining tendency. Drum and Mulla had pronounced twining tendency while Ife Brown had no twining tendency. Based on pooled cluster analysis the dendrogram grouped the varieties in two different major clusters A and B. Cluster A comprised of seven genotypes; Oloyin-Nla, Oloyin-Pelebe, Sokoto, Ife BPC, Modupe, Ife 98-12 and Ife Brown. Cluster B comprised of two genotypes; Drum and Mulla. This implies that genotypes within the same cluster had similar genetic background, while genotypes in cluster A are distant on the chromosome as compare to genotypes on cluster B respectively.Keywords: Genetic evaluation, Vigna unguiculata, Cowpea, Morphological Characters