Examining the Research Gap in Wild Crop Relative Genetic Resources of Nigerian Native Cowpea Populations

Nigeria harbours significant wild relatives and diverse landrace populations of cowpea that represent a rich genetic resource base for breeding against emerging climate, pest, and disease challenges, but systematic characterisation and conservation of this diversity has been insufficiently conducted relative to its potential value. This study examined the research gap in characterisation of wild cowpea (Vigna spp.) genetic resources from Nigeria through scoping review and original germplasm collection and morphological characterisation. A scoping review of ten databases identified 43 publications from 2015 to 2024 on Nigerian cowpea genetic diversity, of which 29 characterised diversity in cultivated materials and only 14 addressed wild Vigna species. Only 6 of these 14 included collections from North East Nigeria, which holds the highest expected wild Vigna diversity based on proximity to the centre of origin. Original germplasm collection expeditions collected 62 accessions of wild Vigna vexillata, V. reticulata, and V. ambacensis from 15 sites in Borno, Adamawa, and Taraba States. Morphological characterisation at IITA Kano substations measured 24 descriptors. Results revealed high levels of morphological diversity for pod traits (pod length CV = 43 percent) and leaflet shape. Preliminary drought tolerance screening identified 8 accessions with significantly higher leaf relative water content under PEG-induced stress (p < 0.05). The study proposes conservation of all 62 accessions at the NACGRAB national genebank and recommends accelerated molecular characterisation of the collection using SSR markers. Keywords: cowpea genetic resources, wild Vigna, genetic diversity, Nigeria, germplasm characterisation