Analyses of virulence and genetic diversity among Xanthomonas axonopodis pv. Vignicola isolates from different cowpea varieties

Xanthomonas is a genus of proteobacteria that causes plant diseases and affects many crops around the world, including tree crops, leaf and fruit vegetables, cereals, tubers, and other crops. The goal of this study was to conduct comparative analyses of morphological, genetic, and virulence factors, as well as to determine the genotype distribution of Xanthomonas axonopodis pv. vignicola (Xav). To determine the cultural morphology, twenty-four (24) pure cultures of Xav from four (4) cowpea varieties were obtained from the International Institute of Tropical Agriculture (IITA) in Ibadan, Nigeria and cultured on nutrient agar with 5% glucose. The isolates’ genomic DNA was extracted and randomly amplified using random amplified polymorphic DNA (RAPD) primers to obtain polymerase chain reaction (PCR) products, which were electrophoresed on 2% and 1.4% agarose gel for purification and polymorphism determination. However, cultural morphology revealed that Xav has a distinctive yellow color with varying intensities. Among the 24 Xav isolates, cluster analysis revealed three (3) morphologies, two (2) major genotypes, and two (2) major virulence genes (16SrRNA and cylA). The correlation between morphology, virulence, and genotype revealed that color intensity is strongly related to genotype as well as pathogenicity of the isolates. As a result of this study’s findings, it is possible to conclude that all of the isolates have pathogenic effects, albeit at varying levels of expression.