ISOLATION AND IDENTIFICATION OF FUNGI ASSOCIATED WITH THE SPOILAGE OF IRISH POTATO (SOLANUM TUBEROSUM L.)
Abstract
ABSTRACT
The isolation and identification of fungi associated with the spoilage of Irish potatoes collected from Lapai, Niger State, Nigeria, were carried out using plating methods (pour plate and streaking techniques). A total of 80 Irish potato tubers—60 healthy and 20 showing symptoms of rotting and discoloration—were collected from three locations: Lapai Central Market, Baddegi Market, and various retail outlets within Lapai town.Five fungal species were identified: Mucor sp., Aspergillus fumigatus, Penicillium sp., Aspergillus glaucus, and Aspergillus flavus. Among these, Mucor sp. and A. fumigatus were the most frequently isolated, while A. flavus was the least encountered. The average diameter of rot caused by the fungal pathogens increased proportionally with concentration across all isolates. Mucor sp. produced the largest rot diameter (60–350 mm), followed by Penicillium sp. (30–230 mm), A. glaucus (10–206 mm), and A. flavus (10–180 mm). The positive control (distilled water) and negative control (mechanical injury) recorded rot diameters of 0.0 mm and 19–270 mm, respectively.Pathogenicity tests revealed that all isolated fungi were pathogenic to healthy Irish potato tubers. Mucor sp. was the most pathogenic (76%), causing rapid disintegration of infected tubers within 14 days of inoculation, followed by Penicillium sp. (68%) and A. fumigatus (61%). A. glaucus (50%) and A. flavus (47%) exhibited the least pathogenicity. Mechanical injury alone showed an appreciable degree of pathogenicity (55%). The physical characteristics of the rots varied among the fungal pathogens: Mucor sp. caused a soft, watery, light-brown rot; A. fumigatus caused a soft rot with black spores; Penicillium sp. produced a soft, green-gray rot; A. glaucus a soft, green-gray rot; and A. flavus a dry rot with black spores. The odor associated with all fungal rots was unpleasant. It is therefore recommended that contaminated Irish potato tubers be properly sorted and eliminated to prevent reinfection and minimize postharvest losses.
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