Prevalence of the Potato Virus Y Strain Composition Impacting Michigan Seed Potato Production

Potato virus Y (PVY) is a complex of multiple strains that cause a variety of foliar and tuber symptoms. Several current strains have potential to result in variety-dependent yield and quality losses. Understanding the local PVY strain population and variety responses are critical for detection and management. From 2019 to 2023, PVY strain composition was monitored across seven Michigan seed potato-producing counties growing prevalent chip, russet, and tablestock market classes. Using multiplex reverse-transcriptase polymerase chain reaction (RT-PCR) methods, PVY strains were identified from potato tuber or leaf samples collected through the certification program (n = 78 positive lots). PVYN-Wi remained most prevalent in Michigan, but tuber necrotic strains PVYNTN and PVYE also continued to be detected. These, as well as some PVYN-Wi isolates, are known to cause necrotic symptoms in tubers, causing yield and quality reductions for susceptible potato cultivars. As in other U.S. potato-growing regions, PVYN-Wi and PVYNTN were most prevalent in Michigan seed potato lots. Of note, mild to severe tuber necrosis was observed in diagnostic samples positive with local PVYN-Wi strains. Parental strain PVYO appeared to re-emerge in 2023 and should be considered in certification and management. Mild or asymptomatic reactions may still lead to yield or quality losses and may pose a risk to more susceptible cultivars. Due to the diversity of strains and varieties prevalent in the Great Lakes region, continued uniform certification is recommended. Information gathered from this and future survey efforts will be valuable for growers, inspectors, and future breeding and selection efforts.