Proactive approaches to managing Potato virus Y in western Washington

Abby Beissinger

Potato virus Y (PVY) is one of the oldest known plant viruses, and can cause significant crop and monetary losses. This project investigated: (i) the timing of PVY inoculation and the effects on detection method sensitivity and symptom expression of infected plants; (ii) the potential sources of PVY inoculum in western Washington by investigating five specialty potato cultivars (Austrian Crescent, Banana, Cal White, Purple Majesty, Rosefin Apple) inoculated with PVYO, PVYNTN, and PVYN-Wi, surveying weed species for PVY infection throughout the year, and surveying certified and non-certified seed potatoes for PVY infection purchased from local garden stores; and (iii) the reasons why Washington seed potato growers choose not to adopt the innovation of Hawaii winter grow-out testing with follow-up laboratory testing. PVY symptoms and detection differed by physiological growth stage. Plants inoculated at emergence had the most severe symptoms when compared to other physiological growth stages, while plants inoculated at emergence revealed low to no variability in PVY detection sensitivity between TAS-ELISA and Immunostrips. Cultivar symptoms varied by PVY strain infection. For all cultivars, mosaic was most common on plants infected with PVYO or PVYNTN. Mottle was most common on plants infected with PVYN-Wi. Leaf drop was uncommon, except on Austrian Crescent when infected with PVYO. Veinal necrosis was most common on plants infected with PVYO or PVYNTN. Because of leaf lesions on control plants, this symptom should not be considered viral. Plants infected with PVYN-Wi had the lowest yield of asymptomatic tubers. In Skagit and Whatcom plots, no weedy plant sample tested positive for PVY by TAS-ELISA. However, 54% of organic non-certified seed purchased from local garden stores produced plants positive for PVYO, PVYNTN, and PVYN-Wi. No plants from conventional certified seed were positive for PVY, but 18% of the organic seed tested positive. The primary reasons for nonadoption related to perceptions of the winter grow-out innovation: it is not relatively advantageous, not compatible with current PVY management practices mandated by the WSDA Seed Potato Certification Program, overly complex, not easy to implement on a small-scale, and impacts are difficult to observe.

Proactive approaches to managing Potato virus Y in western Washington

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