Isolation and Identification of Postharvest Spoilage Fungi Associated with Sweet Oranges (Citrus sinensis) Traded in Kano Metropolis

Abstract

Mycological studies on fungi in apparently diseased sweet oranges (Citrus sinensis) sampled from retailers at Na'ibawa Yan Lemu market in Kano Metropolis was carried out between August and September 2006. The samples were surface sterilized using 85% ethanol and homogenates were cultured on potato Dextrose Agar and incubated aerobically at room temperature for 7 days at 30°C. Pure cultures of the resulting fungal colonies were obtained from the subcultures of the primary plates. These were identified morphologically and microscopically. The investigation revealed that up to 90% of the samples were infected with one or more fungal species. The most predominant pathogenic fungus isolated from the samples was, Aspergillus sp (32.5%); others include Mucor sp. (25%), Penicillium sp (15%), Rhizopus sp (15%), Fusarium sp, (7.5%), and Alternaria sp. (5%). Proper handling from the farm as well as during storage and the avoidance of mixing of diseased ones with the healthy ones were identified as important factors in preventing loss. The use of suitable chemical treatment of the orange is also recommended as means of reducing economic loss due to fungal pathogens.

Key words: Mycological studies, Fungal colonies, Sweet orange, Kano