Strain-specific resistance to Potato virus Y (PVY) in potato and its effect on the relative abundance of PVY strains in commercial potato fields

Authors: FUNKE, CASSANDRA - University Of Idaho; NIKOLAEVA, OLGA - University Of Idaho; GREEN, KELSIE - University Of Idaho; TRAN, LISA - University Of Idaho; CHIKH-ALI, MOHAMAD - University Of Idaho; QUINTERO-FERRER, ARTURO - University Of Idaho; CATING, ROBERT - Oregon State University; FROST, KENNETH - Oregon State University; HAMM, PHILLIP - Oregon State University; OLSEN, NORA - University Of Idaho; PAVEK, MARK - University Of Idaho; Gray, Stewart; CROSSLIN, JAMES - University Of Idaho; KARASEV, ALEXANDER - University Of Idaho

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2016
Publication Date: 1/1/2017
Citation: Funke, C., Nikolaeva, O.V., Green, K.J., Tran, L.T., Chikh-Ali, M., Quintero-Ferrer, A., Cating, R., Frost, K.E., Hamm, P.B., Olsen, N., Pavek, M.J., Gray, S.M., Crosslin, J.M., Karasev, A.V. 2017. Strain-specific resistance to Potato virus Y (PVY) in potato and its effect on the relative abundance of PVY strains in commercial potato fields. Plant Disease. 101:20-28.

Interpretive Summary: Potato virus Y (PVY) is a serious threat to potato production due to negative effects on tuber yield and quality, and in particular, due to induction of potato tuber necrotic ringspot disease (PTNRD). PTNRD is most often associated with emerging strains of PVY that were not detected in the U.S. prior to 2002. Now the emerging strains predominate in all potato production regions. This study documents the change in PVY strains affecting the potato crop planted in the Pacific Northwest and examines some of the factors responsible for the change. Since 2011 the emerging strains have risen from 35% of the total to over 75% while the older strains have decreased from 63% to less than 7%. PTNRD has become more prevalent and is impacting the commercial potato industry. A majority of the potato cultivars widely grown in the Pacific Northwest have a resistance gene(s) that suppress the multiplication of the older strains of PVY, but do not affect the emerging strains. This leads to a greater number of plants being infected with the emerging strains and a greater number of tubers being infected and passing the virus on to the next crop. These resistance genes are one of the major factors driving the emergence and selection of the new strains of PVY.

Technical Abstract: Potato virus Y (PVY) is a serious threat to potato production due to negative effects on tuber yield and quality, and in particular, due to induction of potato tuber necrotic ringspot disease (PTNRD). PTNRD is typically associated with recombinant strains of PVY. These recombinant strains have been spreading in the U.S. for the past several years, although the reasons for this continuing spread remained unclear. To quantitatively 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 several hundred seed lots of various cultivars. A nine-fold drop in the proportion of non-recombinant PVYO isolates circulating in the Columbia Basin potato was documented during this period, from 63% of all PVY-positives 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-positives 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 ca. 24% in 2015. To further address the shift in strain abundance, screen-house 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, which may have resulted in selective multiplication of recombinant strains of PVY under field conditions. The negative selection against the non-recombinant 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 main driving force changing PVY strain composition to predominantly recombinant strains in potato production areas.