Fungal Communities Associated with Manihot esculenta and the In vitro Antifungal Efficacy of a Gelatin-Peppermint Oil Formulation

Adeogun, O. O.*, Fanimokun, O. O., Nwachukwu, J. C

Postharvest Plant Pathology Unit, Department of Botany, University of Lagos, Nigeria

*Corresponding author’s Email: adeogunoluwagbenga@gmail.com, doi.org/10.55639/607.020100112


ABSTRACT

This study investigates the fungal diversity associated with Manihot esculenta (cassava) and evaluates the antifungal efficacy of a gelatin–peppermint oil formulation against the isolated fungi. Fungal samples were collected from various locations in Lagos, Nigeria, over five months, from the phylloplane, phyllosphere, rhizoplane, and rhizosphere habitats. Six fungal species were identified, with Aspergillus flavus, Aspergillus niger, Rhizopus stolonifer, Penicillium sp., Colletotrichum sp., and Macrophomina phaseolina being the most prevalent. Diversity analysis revealed that the rhizoplane harboured the highest species evenness (H’ = 1.3708, D = 0.7427), while the rhizosphere exhibited the least diversity (H’ = 1.0872, D = 0.6593). Pathogenicity tests confirmed that Colletotrichum sp. and Macrophomina phaseolina caused typical fungal symptoms, including chlorosis and necrotic lesions. The in vitro antifungal assessment demonstrated statistically significant inhibition of mycelial growth across all tested species (two-way ANOVA, p < 0.0001 in all cases; Tukey’s HSD post hoc test). For Aspergillus flavus, the control group showed 4.15 cm of radial mycelial growth, whereas treatment with 10% peppermint oil in gelatin resulted in only 0.65 cm of growth (84.3% inhibition). Similarly, Rhizopus stolonifer exhibited 4.16 cm of radial growth in the control group, while the 10% peppermint oil formulation limited growth to 0.28 cm (93.3% inhibition). These results confirm the potential of gelatin- based peppermint oil formulations as effective biocontrol agents for managing cassava fungal diseases, while also highlighting the ecological variation in fungal diversity across cassava-associated habitats. This approach offers a sustainable alternative to chemical fungicides.

KEYWORDS
Cassava,
Peppermint Oil,
Gelatin,
Fungi.

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