Comparative in vitro Antifungal Efficacy of Botanical Seed Oils Against Geotrichum candidum Associated with Tomato Fruit Rot in Gombe State, Nigeria

In Nigeria, tomato production plays a major role in food security and income generation for farmers and traders Northern Nigeria. In Gombe State, as elsewhere in the north, field and postharvest losses resulting from microbial infections remain a major setback to sustainable tomato production and marketing. This study evaluated the antifungal efficacy of four botanical seed oils: neem, moringa, mahogany and castor, against Geotrichum candidum causing sour rot of tomato fruit. The fungus was isolated from rotten tomato fruit, cultured on Potato Dextrose Agar and identified using morphological (through microscopy), and molecular (DNA isolation, ITS-PCR, gel electrophoresis and Sanger sequencing) techniques. Pathogenicity test was carried out following Koch's postulates. Antifungal efficacy was assessed at four concentrations (0.5. 1, 1.5 and 2.0%) respectively using the poisoned food method in a 4×4 factorial Completely Randomised Design, with Mancozeb and untreated agar as controls. The study was conducted entirely in vitro on agar plates; efficacy on tomato fruits was not assessed. Data were collected on radial inhibition and percent growth reduction and were analysed by two-way ANOVA, Duncan's Multiple Range Test and linear regression. The results showed that all the four oils significantly inhibited mycelial growth in a concentration-dependent manner, with Duncan's Multiple Range Test establishing a significant potency ranking, Moringa (80.19%) > Neem (71.48%) > Mahogany (55.93%) > Castor (48.70%), and Moringa at 2.0% producing the highest inhibition (88.15%). The Oil × Concentration interaction was not significant. These findings confirm G. candidum as the causal agent of tomato sour rot in the study area and and identify moringa seed oil as the most promising candidate among the oils tested for further in vivo evaluation as part of integrated postharvest disease management.