IN VITRO effects of garlic (Allium sativum L.) and African basil (Ocimum gratissimum L.) on pathogens isolated from rotted cassava roots

Six fungal pathogens causing rot in post-harvest cassava tuberous roots were investigated in vitro for the study of the fungi toxic effects of Allium sativum (L) and Ocimum gratissimum (L.) using aqueous extraction methods. Fungi were isolated by cutting rotted tissue at the interface between healthy and infected portions of the root. Pathogenicity tests revealed that Fusarium oxysporum, F. solani, Botryodiplodia theobromae, Macrophomina phaseolina, Penicillium oxalicum and Aspergillus niger induced rot in healthy cassava tubers after 8 days of re-inoculation, with P. oxalicum as the most virulent. Four different extract concentrations were obtained from each plant part by blending 25, 50, 75 and 100g in 100ml of sterile distilled water (SDW).The fungi toxic effect of the extracts showed that A. sativum had effective inhibition (25.2-86.9%) on mycelial growth of all tested fungi, while extracts of O. gratissimum showed slight to moderately effective inhibition (0.9 to 64.5%) on mycelial growth of all fungi, with the exception of B. theobromae and M. phaseolina, which showed the lowest percentage of inhibition with both plant extracts. The most toxic effect of the extracts was observed with A. sativum at 10%, with significant (P<0.01) inhibition on all fungi tested. The study showed the potential of crude extracts of A. sativum and O. gratissimum on fungal pathogens affecting cassava. This potential of the crude extract of these plants provides an alternative to farmers to reduce and control cassava rot, since they are inexpensive, non-phytotoxic and easy to prepare.