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The antimicrobial potential of Azadirachta indica seed oil against seed-borne pathogens of Tectona grandis at different concentrations (2%, 4%, 6%, 8%, and 10%) was investigated. T. grandis seeds were obtained from the seed bank of FRIN Ibadan and taken to the Plant Pathology Laboratory of Forestry Research Institute of Nigeria Ibadan, for the isolation of fungal pathogens. The seeds were disinfected by dipping in sodium hypochlorite and placed on Potato dextrose agar (PDA) to isolate pathogenic fungi. Botanical oil extract was prepared from Azadirachta indica seed. The seed-borne fungi isolated were Fusarium oxysporuum, Curvularia lunata, Rhizopus nigricans, Aspergillus niger, and Trichoderma viride. Results of the antifungal assay showed that neem seed oil extract at various concentrations inhibited the mycelial growth of the test organisms. However, the inhibitory effects of the oil extract increased with higher concentrations. The percentage inhibition for each organism at different concentrations varies, the highest percentage inhibition for Trichoderma viride was 100% at 6% concentration, Rhizopus nigrican was 100% at 8% concentration and Cuvularia lunata was 95.23% at 10% concentration respectively. This experiment, therefore, concludes that essential oil from neem seed contains secondary metabolites having the potential to serve as bio-fungicides in the management of Trichoderma viride, Rhizopus nigricans, and cuvularia lunata, seed-borne pathogens of Tectona grandis seeds.
Oyelowo et al. (Sat,) studied this question.