Post-Harvest Fungal Diseases of Stored Sweet Potatoes (Ipomoea batatas (L.) Lam) in Three Markets of Jos, Plateau State

Background and Objective: One of the greatest problems of food production in Nigeria is that of storage, which leads to post-harvest losses, especially in tubers like sweet potato, which are caused by fungi. This study aimed to isolate, identify, and evaluate the pathogenicity of fungal species associated with sweet potato tuber rot in three markets within Jos, Nigeria. Materials and Methods: Diseased tubers were collected, and fungal isolates were cultured on potato dextrose agar (PDA) which was prepared by boiling 200 g of peeled potatoes in 1 L of distilled water, filtering the infusion, and adding dextrose and agar before sterilization. Fungal isolation was done, where the diseased sweet potato tissues were aseptically excised and inoculated on PDA. Plates were incubated at 25°C for 3-7 days, and fungal colonies were purified through subculturing with streptomycin added to suppress bacterial growth. Identification of fungal isolates was based on morphological characteristics and compared with existing descriptions. Pathogenicity tests involved inoculating healthy, surface-sterilized sweet potato tubers with pure fungal cultures using a cork borer technique. Tubers were sealed with Vaseline, incubated for 14 days at room temperature, and assessed for rot development. This methodology ensured accurate fungal identification and pathogenicity assessment. A Completely Randomized Design (CRD) with three replicate plates was used, and data were analyzed using Two-way ANOVA with LSD at 5% for mean comparison. Results: Morphological identification confirmed the presence of Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus, Fusarium spp., Penicillium spp., Rhizopus spp., and two unidentified fungi. The frequency of fungal occurrence varied across the markets. Aspergillus niger was the most prevalent species (22.44%), followed by Fusarium spp. (17.0%) and Aspergillus flavus (16.32%). Penicillium spp. and the unidentified fungi had the lowest occurrence. Pathogenicity tests revealed that Aspergillus flavus and Fusarium spp., were the most aggressive pathogens, causing 43.86 and 42.65% weight loss, respectively, with rot diameters of 28.30 and 19.95 cm. Aspergillus niger and Aspergillus fumigatus exhibited moderate pathogenicity, while Rhizopus spp. and Penicillium spp., were the least pathogenic. Statistical analysis (LSD = 19.41, p<0.001) confirmed significant differences among fungal species in pathogenicity. Conclusion: The findings highlight the major fungal pathogens responsible for sweet potato spoilage in storage and markets, with Aspergillus flavus and Fusarium spp., posing the highest threat. Future studies should focus on developing biocontrol strategies to mitigate post-harvest losses and improve sweet potato storage conditions.