Identification and molecular characterisation of cercospora leaf spot disease pathogen on cowpea (Vigna unguiculata L. Walp)

Cercospora leaf spot disease (CLSD) is a serious constraint to the production of cowpea worldwide, especially in the tropics. This study was conducted to identify the causative agent of CLSD on cowpea accessions. Infected cowpea leaf samples were collected from established cowpea experimental field at the Institute of Agricultural Research and Training (IAR&T), Ibadan. The leaves were placed on potato dextrose agar (PDA) and sub-cultured to obtain pure fungi isolates. Nucleic acid extraction from the pure culture was carried out at the molecular laboratory of National Horticultural Research Institute (NIHORT), Ibadan. Polymerase chain reaction (PCR) was carried out to amplify fungi nucleic acid using ITS1 and ITS4 universal primers. The amplicon obtained were subjected to Basic Alignment Search Tool (BLAST) to determine the sequence homology. These sequences were compared with known sequences on the National Centre for Biotechnology Information (NCBI) database. The sequences analysed had similarity with Cercospora canescens (MK029364.1 and MW756382.1) deposited on the NCBI database. This study confirms that C. canescens is the causal pathogen of CLSD found on the infected cowpea leaves.