Identification and characterization of causative agents of brown leaf spot disease of cassava in Kenya

Abstract

This study was conducted to investigate the causal agent of brown leaf spot (BLS) of cassava in Kenyan fields. Infected cassava leaf samples showing BLS disease symptoms were collected from Kenya Agricultural and Livestock Research Organization (KALRO) experimental fields in central and western Kenya. Fungal pathogens associated with the disease were isolated from the cassava leaf samples on potato dextrose agar amended with antibiotics. Three fungal isolates, belonging to the genera Colletotrichum, Alternaria, and Cladosporium, were identified as the causative agents of BLS with relative prevalence of 41%, 24%, and 18%, respectively. Susceptible cassava variety TME 204 was inoculated with single and combinations of purified isolates of the three pathogens in a randomized design in the greenhouse. The combination of the three isolates resulted in typical BLS symptoms as observed in the field. The findings of this study would help to understand the disease, contribute to its better management, and eventually alleviate food insecurity, especially in the regions where cassava is a major staple food and a source of income.