Antimicrobial Effect of Some Plant Extracts on Plant Pathogens that Cause Food Spoilage

Aims: To determine the preservative effect of methanol extracts of Azadirachta indica, Euphorbia heterophylla and Tithonia diversifolia on fruits as an alternative to chemicals being used for preservation.

Place and Duration of Study: The study was carried out at the Department of Biological Sciences, Afe Babalola University, Ado Ekiti between September 2017 and February 2018.

Methodology: Pour plate method was used in the isolation of microorganisms from the fruits used and this were pineapple, banana, watermelon pawpaw and orange.

Results: Bacteria isolated were Acinectobacter ursingii, Bacillus subtilis, Bordetella trematum, Klebsiella pneumoniae, Propionibacterium acnes, Staphylococcus aureus and Staphylococcus epidermidis. Fungi isolated were Aspergillus niger, Fusarium avenaceum, Fusarium oxysporum, Neurospora crassa, Penicillum notatum and Rhizopus stolonifer. Different concentrations of the plant extracts (100 mg/ml, 80 mg/ml, 50 mg/ml and 30 mg/ml) were used on the test organisms and zones of inhibitions were determined which increased with increase in concentration. Methanol extracts of the bark of Azadirachta indica and Tithonia diversifolia leaves had greater antibacterial activity as they reduced the growth all the bacterial isolates especially Staphylococcus aureus at 100 mg/ml with a zone of inhibition of 41.00c mm and 17.75b mm respectively. All the extracts were not active against Acinectobacter urisingii. All concentrations of the methanol extract of the bark of Azadirachta indica and Tithonia diversifolia inhibited the growth of Aspergillus niger and Penicillum notatum for seven and four days respectively. Only 100 mg/ml of methanol extract of the bark of Azadirachta indica inhibited Fusarium oxysporum for seven days. The shelf life of watermelon treated with all the extracts was extended for eight days. That of pineapple, pawpaw, banana and orange was extended for four days using all the extracts.

Conclusion: These results support the potential use of these plant extracts in the management of diseases caused by tested plant pathogenic organisms.