Identification and pathogenicity of Nigrospora sphaerica and Curvularia penniseti associated with leaf spot disease of cowpea (Vigna unguiculata (L.) Walp.) in Nigeria

Abstract Pathogenic fungi are one of the main causes of plant diseases due to their ability to colonise plants and rapidly spread disease. Cowpea is one of the most highly consumed grain legumes in Nigeria, but its yearly production is usually affected by fungi attacks. Disease presenting browning of the aerial parts of the cowpea plant was observed during the dry season between 2021 and 2022 in the country. This disease caused stunted growth in the affected plant stand. The fungi were isolated from the symptomatic aerial parts. The fungi were viewed under the microscope and identified by molecular and phylogenetic tools using the Internal Transcribed Spacer (ITS) gene region. The fungi isolated from the symptomatic aerial part of cowpea were identified as Nigrospora sphaerica and Culvularia penniseti. The pathogenicity of the isolated fungi was tested on detached leaves and stems and on intact cowpea seedlings. The test gave a positive result, which confirms the pathogenicity of the isolated fungi on the cowpea plant. This is the first report of N. sphaerica and C. penniseti infecting cowpea cultivated on farmland in Nigeria. Early detection of foreign fungi causing disease in the country’s cowpea crop will aid researchers in addressing the negative effects on crop yield.