SENSITIVITY ASSESSMENT OF SOIL-BORNE PATHOGENS TO ETHANOLIC AND METHANOLIC LEAF EXTRACT OF CHROMOLAENA ODORATA (L.) USING DILUTION AND DIFFUSION ASSAY METHODS

Abstract

The sensitivity of pure isolates of Phytophthora colocasiae and Fusarium oxysporum to methanolic and ethanolic leaf extracts of C. odorata was evaluated using diffusion(agar and disc diffusion) and dilution(broth and agar dilution) assays. Basic quantitative and qualitative analyses of the extracts were determined. The experiment was laid out as factorial in Completely Randomized Design (CRD) with three replications. Data collected were adequately analyzed using Univariate approach and Least Significance Difference (LSD) test to separate significant at P ≤ 0.05. Observations from the study revealed that antimicrobial activities of the plant extracts were dependent upon the assay methods used which varied significantly. Ethanolic leaf extracts of C. odorata significantly increased the inhibition zone diameter (IZD) against F. oxysporum when compared to methanolic leaf extracts of same plant. However, significant differences were not observed in IZD between ethanolic and methanolic leaf extracts against P. colocasiae(12.67 ± 0.79 and 12.56 ± 0.74). Ethanolic extracts of C. odorata were found to possess higher inhibitory effects shown by the wider inhibition zone against the pathogens using disc diffusion assay. There were significant and non- significant reductions respectively in IZD of F. oxysporum and P. colocasiae with increased concentrations of the leaf extracts. The methanolic and ethanolic extracts of C. odorata showed significant higher inhibitory activities against the pathogens at MICof 6.25 and25 mg/ml respectively, inhibiting the growth of the pathogens completely.