Efficacy of Methanolic Leaf Extract of Hyptis suaveolens and Moringa oleifera in the Control of Soil-Borne Pathogens

Aim: Soil-borne diseases are difficult to control because they are caused by pathogens that can survive for long periods in the absence of the normal crop host and often have a wide host range including weeds. This present study was design to assess the antifungal assay dependent effect of methanolic extracts of Hyptis suaveolens and Moringa oleifera on Phytophthora colocasiae and Fusarium oxysporum.

Methods: The presence of biologically active ingredients (alkaloid, saponin, tannins, flavonoid, terpenoids, tannins, steroids, hydrogen cyanides, phenols and glycoside) in the leaf extracts was investigated using standard procedures. The antifungal activities of the plant extract were tested against Phytophthora colocasiae and Fusarium oxysporum using disc and well diffusion assays.

Results: The results of the phytochemical evaluated showed that H. suaveolens, contained significantly higher alkaloids, saponins, hydrogen cyanide, flavonoids and phenols than M. oleifera, while on the other hand, M. oleifera contained significantly higher terpenoids, tannins, steroids and glycosides. Consequently, H. suaveolens extract similarly recorded significantly (P < 0.05) higher inhibition on the organisms as compared to M. oleifera. The disc diffusion assay method was more sensitive than the well diffusion assay. H. suaveolens at 100 mg/ml using disc diffusion assay method showed higher inhibition on both P. colocasiae and F. oxysporum. While M. oleifera recorded higher inhibition on F. oxysporum at 50 mg/ml and P. colocasiae at 100 mg/ml using the disc diffusion assay method. MIC was lowest with H. suaveolens (12.5 mg/ml) against F. oxysporum.

Conclusion: These results promote the identification of actives substances from these plants for use as lead molecules in the development of new fungicides for the control of Phytophthora colocasiae and Fusarium oxysporum.