Tropical Plant Research

A. O. Akanmu, O. J. Olawuyi, O. B. Bello*, O. A. Akinbode3, T. Aroge, B. Oyewole and A. C. Odebode

Abstract:
The ethanol extracts of Ficus asperifolia, Mormordica charantia, Anacardium occidentals and Psidium guajava were evaluated sole and in treatment combinations at 25, 50 and 75mg ml^-1 concentration levels against the mycelial growth of Macrophomina phaseolina of Cowpea. The pathogen was cultured on plates containing botanicals amended Potato Dextrose Agar (PDA) in three replicates while only ethanol treated PDA tested plates served the control experiment. The radial growths were recorded at 4^th, 6^th and 8^th day after inoculation. Data obtained were analysed using the SAS software program version 9.2. The extract of Mormordica charantia was the most effective in the botanical treatments alone. The most significant inhibition of Macrophomina phaseolina were observed from the combined treatments of Ficus asperifolia, Mormordica charantia and Anacardium occidentals (3.11 cm), followed by Mormordica charantia and Psidium guajava (3.29 cm), then combination of four extracts; Ficus asperifolia, Mormordica charantia, Anacardium occidentals and Psidium guajava (3.53 cm), then Mormordica charantia and Anacardium occidentals (3.84 cm). Other treatments, either alone or in combination produced significant result compared to the control experiment (6.94 cm). However, the efficacy of botanicals increased with concentration and also significantly correlated with time and reduction in mycelia extension of the pathogen. More so, variability in the antifungicidal potentials of the botanicals on Macrophomina phaseolina ranges from 15.93% to 34.06% according to Eigen proportions. The treatment combinations of; Ficus asperifolia, Mormordica charantia and Anacardium occidentals at 75mg ml^-1 concentration level produced the most inhibitory effect against Macrophomina phaseolina in vitro. However, the untreated plates did not show inhibitory effect on the mycelial growth of the pathogen. Therefore, combined treatments of botanicals could be a potential source in the practise of plant disease control.