Strain-Specific Resistance to Potato virus Y (PVY) in Potato and Its Effect on the Relative Abundance of PVY Strains in Commercial Potato Fields

Abstract

Potato virus Y (PVY) is a serious threat to potato production due to effects on tuber yield and quality, in particular, due to induction of potato tuber necrotic ringspot disease (PTNRD), typically associated with recombinant strains of PVY. These recombinant strains have been spreading in the United States for the past several years, although the reasons for this continuing spread remained unclear. To document and assess this spread between 2011 and 2015, strain composition of PVY isolates circulating in the Columbia Basin potato production area was determined from hundreds of seed lots of various cultivars. The proportion of nonrecombinant PVYO isolates circulating in Columbia Basin potato dropped ninefold during this period, from 63% of all PVY-positive plants in 2011 to less than 7% in 2015. This drop in PVYO was concomitant with the rise of the recombinant PVYN-Wi strain incidence, from less than 27% of all PVY-positive plants in 2011 to 53% in 2015. The proportion of the PVYNTN recombinant strain, associated with PTNRD symptoms in susceptible cultivars, increased from 7% in 2011 to approximately 24% in 2015. To further address the shift in strain abundance, screenhouse experiments were conducted and revealed that three of the four most popular potato cultivars grown in the Columbia Basin exhibited strain-specific resistance against PVYO. Reduced levels of systemic movement of PVYO in such cultivars would favor spread of recombinant strains in the field. The negative selection against the nonrecombinant PVYO strain is likely caused by the presence of the Nytbr gene identified in potato cultivars in laboratory experiments. Presence of strain-specific resistance genes in potato cultivars may represent the driving force changing PVY strain composition to predominantly recombinant strains in potato production areas.

Serological, molecular and immunofluorescent evidence for interference competition between isolates of Potato virus Y

“…It seems possible that cv. Satina has strain‐specific resistance, particularly against PVY O , similar to that recently found in three other potato cultivars (Funke et al ., ).…”

“…Moreover, the results demonstrate the occurrence of complete or at least partial cross‐protection among PVY isolates, with the NTN isolates being evidently more fit than their counterparts. The competitive advantage of the NTN isolates over the other isolates in mixed infections is an important factor that is responsible for the current predominance of these PVY forms in potato crops in many regions of the world (e.g., Yin et al ., ; Funke et al ., ). The competing strains showed a tendency towards separation from each other in host tissues.…”

Potato Cultivar and Seed Type Affect the Development of Systemic Potato virus Y (PVYN-Wi) Infection

“…PVY N does not induce an HR response in potatoes (i.e., Ny tbr or Nc tbr are not induced), whereas PVY N induces vein necrosis in tobacco (Cockerham 1970;Jones 1990;Karasev and Gray 2013;Rowley et al 2015;Singh et al 2008, and reviewed in Funke et al 2017). Similar to PVY N , PVY N-Wi does not induce an HR response in potato and causes vein necrosis in tobacco (Cockerham 1970;Jones 1990;Karasev and Gray 2013;Rowley et al 2015;Singh et al 2008; and reviewed in Funke et al 2017). PVY N-Wi infection of potato plants may be asymptomatic or result in transient mild mosaic patterning on foliage (Karasev and Gray 2013).…”

“…PVY N-Wi infection of potato plants may be asymptomatic or result in transient mild mosaic patterning on foliage (Karasev and Gray 2013). Interactions between specific PVY strains and potato cultivar hosts affect viral pathogenicity, potato quality and yield loss (Funke et al 2017). In this study, we focused on the PVY N-Wi strain that has increased in prevalence in Montana and the United States since its initial detection in 2002 (Karasev 2016).…”

Methods to Study the PVY Population in the Potato

“…The recombinant PVY variants are found to be prevalent worldwide in potato -growing area and are replacing the non-recombinant strains PVY C , PVY O and PVY N (Funke et al, 2017, Davie et al, 2017. In the UK, a survey of the molecular diversity of PVY indicated that 80-90% belong to the recombinant European PVY NTN group (Davie et al, 2017).…”