Botryosphaeriaceae associated with baobab (Adansonia digitata L.) and marula (Sclerocarya birrea A. Rich.) in agroforestry systems in Kenya

Abstract

Indigenous fruit trees such as baobab and marula provide key nutrients and income for smallholders and enhance diversification of agroforestry systems in the drylands of Sub Saharan Africa. Cankers and diebacks are increasingly observed impacting baobab and marula in domestication trials and farms in Kenya, but little is known on disease occurrence and associated pathogens. Field disease incidence and severity was assessed. Fungal isolation and molecular identification was performed and pathogenicity of isolates was evaluated on baobab, marula and additional agroforestry trees. Nine taxa morphotypes belonging to genera Lasiodiplodia, Neofusicoccum and Dothiorella were identified co-occurring in both symptomatic and asymptomatic plant material. Seedlings inoculated with isolates of L. pseudotheobromae, L. theobromae and N. parvum showed similar symptoms with various degree of virulence. These findings suggest that species of Botryosphaeriaceae may occur as endophytes and also act as a disease complex, with the potential of infecting a wide range of trees in Eastern Kenya. Further investigation of ecology and impact of this potential threat to agroforestry systems in the African drylands, need to be performed in order to develop mitigation strategies. Key words: Adansonia digitata, agroforestry, Botryosphaeriaceae, Sclerocarya birrea, tree cankers.