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Indian Phytopathology, 2025 (Scopus)
The study was conducted to investigate the causal agents of brown leaf spot (BLS) in cassava in the Bono Region of Ghana from 2021 to 2023. Fungal pathogens associated with the diseased leaves were isolated on potato dextrose agar (PDA) amended with ampicillin. Fungal species belonging to the genus Colletotrichum were identified as the causative agents of BLS, with a relative prevalence of 40%. All the Colletotrichum species acted synergistically to produce the typical BLS symptoms observed on farmers’ fields. Based on morphological characterization, four types of Colletotrichum conidia end shapes were distinguished: conidia rounded on both ends, one round and one sharp-ended conidia, tapering (pointed) at both ends, and apex broadly rounded ends. Microscopic examination revealed two distinct conidia morphologies: falcate and cylindrical. On PDA, isolates developed pinkish acervuli and a pink- to- orange colour. The average spore dimensions showed significant differences between the clades. All clades were not significantly different between conidial lengths in clades (A, B, C, D, E, G, I, and J), while clades (F and H) were significantly different from one another at (P < 0.001). Molecular identification using multi-locus analysis of the internal transcribed spacer (ITS) and actin (ACT) regions revealed the putative pathogens as belonging to the genus Colletotrichum species complex that included C. fructicola, C. siemense, and C. gigasporum. The pathogenicity test performed on healthy cassava seedlings produced similar symptoms of BLS as observed in the fields.