Abstract

Botryodiplodia theobromae, a common rot fungus, causes serious economic losses in cultivation of many different crops such as cocoa, mango, banana and yam. Determination of infectious routes of plant pathogens and their mechanisms of infection are of great importance in any disease control programme. Until this work, no investigation had been made into cross infectivity of different isolates of the fungus in Ghana. The aim of the study therefore was to investigate cross infectivity of various B. theobromae isolates from cocoa, mango, banana and yam. Mature fruits of cocoa, mango and banana and yam tubers with symptoms of B. theobromae rot were collected from farms within four regions in Ghana for fungal isolation. The isolated fungi from the four crops were developed into pure cultures on potato dextrose agar (PDA). Five-day old pure cultures were separately inoculated into healthy mango fruits and cocoa pods. This was followed by daily measurement of lesion diameter, and observation of the fruit internal tissue damage caused by the fungi infection. The results indicated that the symptoms of rot and mycelia characteristic of the B. theobromae were visible within two days. The cocoa, mango, banana and yam isolates of B. theobromae were found to be virulent with similar pathological effects in the experimental crops, that is, cocoa and mango. It is concluded from this work that B. theobromae isolates from the four different crops, that is, cocoa, mango, banana and yam in Ghana’s forest agricultural zones are infectious and have damaging effects on other neighbouring crops with economic consequences. The findings cast doubts on the mixed- or inter-crop system which is usually adopted to control fungal rot in plantation farms.

Key words: Botryodiplodia theobromae, cross infectivity, mixed-crop system, inter-cropping.