Tuber Symptoms Associated with Recombinant Strains of Potato virus Y in Specialty Potatoes Under Western Washington Growing Conditions

Abstract

This study documented the presence of PVYo, PVYNTN, and PVYN-Wi strains in western Washington in 2012 and 2013, representing the first detections of PVYNTN and PVYN-Wi in this potato growing region. Chieftain and Yukon Gold plantings showed an unexplained shift to a higher proportion of PVYN-Wi in 2013 compared to 2012. In 2012, 56.4 % of positive plants pooled across cultivars were affected by PVYN-Wi while 39 % were affected by PVYO. In 2013, PVYN-Wi was the highest represented strain at 79.3 %. Testing of non-symptomatic plants from pre-selected survey sites showed PVYN-Wi comprised 69.5 % in 2012 and 100 % in 2013 of the total strains identified. PVY also impacted the quality of tubers. In both a field and a greenhouse trial, there was a clear association between PVY plant infections and suberized canoe-shaped cracks in progeny tubers. Non-symptomatic (healthy) plants had significantly fewer cracked, and/or discolored and/or malformed tubers compared to suspect and symptomatic plants. Plants negative for PVY at grow-out did not produce cracked tubers while plants positive for PVY produced 22–32 % cracked tubers. Results from subsequent on-farm tuber surveys suggested the same trend, although the relationship was not as clear cut, but observations were derived from sampling in 2013 when sample sizes were limited. Because of the close geographic and economic connection between seed and ware potato production in western Washington and the results derived from these studies, we suggest a systematic and regional approach to PVY management that includes adjustments to current seed certification practices; new research and educational programs that improve knowledge of PVY biology, transmission, and effects on tuber quality; and new field management strategies to reduce vector and virus spread.