A new study published in the journal Plant Disease has identified several Fusarium species responsible for potato dry rot in Colorado’s San Luis Valley, including one species not previously reported in the United States.

The research was conducted by plant pathologists at Colorado State University’s San Luis Valley Research Center and examined tubers collected from commercial potato production areas during the 2023 and 2024 seasons. The San Luis Valley is the state’s primary potato-growing region, accounting for the vast majority of Colorado’s production.

Fusarium dry rot is widely recognized as one of the most significant post-harvest diseases affecting stored potatoes worldwide. The fungal disease typically develops through wounds on harvested tubers and can lead to substantial storage losses and quality deterioration.

Using both morphological observations and molecular analysis, the researchers identified four species associated with dry rot symptoms in the sampled tubers: Fusarium oxysporum, Fusarium sambucinum, Fusarium clavum, and Fusarium solani. The integration of genetic sequencing with traditional fungal identification methods allowed the team to classify isolates into distinct species groups and evaluate their biological characteristics.

The study reports that Fusarium clavum represents a newly documented species associated with potato dry rot in the United States. According to the authors, this finding highlights the diversity of fungal pathogens present in potato storage systems and underscores the importance of accurate pathogen identification.

Pathogenicity tests conducted on several potato cultivars revealed differences in aggressiveness among the species. Fusarium solani caused the most severe infections in the cultivars evaluated, while other species showed varying levels of virulence.

The researchers also measured fungal growth rates under controlled laboratory conditions and observed significant differences among the species, with F. sambucinum displaying the fastest radial growth over time.

The authors note that identifying the species composition of Fusarium populations is important for the development of effective disease management strategies. Because species can differ in their aggressiveness and response to fungicides or storage conditions, accurate diagnosis may help growers and storage operators adapt disease-control practices more effectively.

The findings contribute to a growing body of research on post-harvest diseases in potato supply chains and provide a foundation for further work on disease mitigation strategies in the San Luis Valley and other major potato-producing regions.

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This research was conducted by Dr. Hafiz M. Usman Aslam, Postdoctoral Fellow in Plant Pathology at the San Luis Valley Research Center (SLVRC), Colorado State University (CSU), under the supervision of Dr. Mohamad Chikh-Ali, Program Leader of Plant Pathology at the SLVRC, CSU, with laboratory assistance from Jeremy Daniel.