Pathogenicity evaluation of fungal isolates associated with dry rot on cold-stored potato tubers for the identification of predominant pathogens

Dry rot is one of the most destructive postharvest diseases of potato tubers, primarily attributed to fungal pathogens capable of surviving and initiating infection under low-temperature storage conditions. Although several Fusarium species have been recognized as major causal agents worldwide, the pathogenic diversity of fungi associated with cold-stored potatoes in Korea remains less characterized. In this study, twelve fungal isolates obtained from dry rot lesions were taxonomically placed using ITS sequencing and evaluated for their pathogenicity on wounded tubers of the cultivar 'Superior' during cold storage (4 °C for 5 weeks). Lesion development was quantified to compare pathogenic activity among isolates. All isolates induced rot, although pathogenicity varied significantly among species. Fusarium spp., including tested isolates belonging to the F. oxysporum species complex (FOSC), F. boothii, and the F. fujikuroi species complex (FFSC), produced substantial lesions, and Clonostachys rosea, typically regarded as a biocontrol agent, also caused measurable rot under cold conditions. These results provide foundational information regarding the fungal species associated with dry rot in cold-stored potatoes under the specific conditions tested. Our findings suggest that management strategies should consider not only well-known Fusarium species but also opportunistic fungi capable of colonizing potato tubers at low temperatures.