A study was undertaken to investigate the antifungal effect of essential oil and solvent extracts of dried leaves of Ocimum gratissimum L. in the quest for a possible bio-fungicide. Previous studies unveiled, rice farming regions of Cameroon were endemic to Bipolaris oryzae and Alternaria padwickii causal of brown-spot and stack-burn diseases respectively. A comparative in vitro study exploring the antifungal effect of Ocimum gratissimum L. dried leaves extracts and a local synthetic fungicide (Chlorothalonil 550 and 100 g L-1 Carbendazim referred to as Banko-plus) against these two phytopathogens using the supplemented medium technique was setup. Essential oil obtained through hydrodistillation stood at pars from ethanol extract, cold water extract, hot water extract and exhibited the best antifungal activity on Bipolaris oryzae and Alternaria padwickii at (150 ppm), marked by 86.17 and 100% growth inhibition, respectively. The synthetic fungicide strongly inhibited B. oryzae and A. padwickii at 10,000 ppm with 69.11 and 100% growth inhibition, respectively. Strong resistance was exhibited by B. oryzae against Banko-plus at lower concentrations, shedding light on the inefficiency of farmers to control brown-spot disease with this systemic fungicide in Cameroon. Ethanol and cold water exhibited some exploitable antifungal activity. Hot water extract showed no inhibitory activity at all tested concentrations, but paradoxically activated growth at all tested concentrations. This study paved the path for further field studies towards the exploitation of the antifungal potentials of Ocimum gratissimum L. essential oil, ethanol and cold water extracts for seed treatment in Cameroon rice fields.
Bengyella Louis, Julienne Nguefack and Pranab Roy, 2011. Evaluation of Antifungal Potential of Ocimum gratissimum Extracts on Two Seedborne Fungi of Rice (Oryza sativa L.) in Cameroon. Asian Journal of Biological Sciences, 4: 306-311.