Isolation and Characterization of Fungi Associated with Orange Spoilage in Maiduguri, Borno State

Fruits play a vital role in human nutrition by supplying essential vitamins and minerals for maintaining good health. This research investigated fungal pathogens associated with orange fruit (Citrus sinensis) spoilage sold in four locations in Maiduguri, Borno State, Nigeria. The samples were surface sterilized with ethanol, and the homogenates were cultured on Potato Dextrose Agar and incubated aerobically at room temperature for 7 days at 30 °C. The pure cultures obtained were identified morphologically and microscopically. The investigations revealed that the samples were infected with several fungal species. The most predominant fungi isolated from oranges were Aspergillus niger and Aspergillus flavus having the highest frequency and distribution from all sampling points (25%). Aspergillus oryzae and Rhizopus stolonifer had 18.75% occurrences each, while Fusarium species had 12.5%. Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, and Aspergillus oryzae produced the same symptoms and signs as observed in the healthy orange fruits, except for Fusarium species, which were not able to grow and produced spoilage conditions on the inoculated healthy orange fruits after 5 days. Aspergillus species produce several toxic metabolites, like aflatoxins and ochratoxins, which are important toxins worldwide because of their hazards to human health. Therefore, precautions should be taken when handling spoilt orange fruits.