Serological Properties of Ordinary and Necrotic Isolates of Potato virus Y: A Case Study of PVYN Misidentification

Abstract

In the course of a multi-year survey of Potato virus Y (PVY) incidence and diversity in the U.S. seed potato crop, an unusual PVY variant was identified in low but significant levels in multiple states. This variant, PVY O -O5, was initially detected by a commercially available PVY N -specific monoclonal antibody, 1F5. This antibody is widely used by U.S. Seed Certification programs to test for PVY N and is one of two antibodies designated by the North American Plant Protection Organization (NAPPO) for preshipment testing of tuber lots that are to be transported between countries. Consequently, PVY N positives identified by the 1F5 antibody have triggered quarantine actions, prevented cross-border shipments and impacted trade. Here, we demonstrate by a variety of methods that the PVY O -O5 is a variant within the ordinary PVY strain (PVY O ). Specifically, the PVY O -O5 variant likely arose due to a single amino acid substitution within the capsid protein. This variant does not induce vein necrosis in tobacco or tuber necrosis in susceptible varieties of potato. Furthermore, it is identified by RT-PCR based diagnostics as PVY O and it has a typical PVY O genome sequence. We demonstrate that another PVY N specific monoclonal antibody, SASA-N, recognizes an epitope distinct from that recognized by 1F5, and correctly identifies the PVY O -O5 variants as belonging to the PVY O serotype. Since the PVY O -O5 variant is present in many seed producing states and misidentification of PVY O -O5 as PVY N/NTN has clear quarantine implications for export shipments of potato, the limitations of the commercially available monoclonal antibodies should be considered in any certification or phytosanitary testing program.Resumen A lo largo del estudio de varios años sobre la incidencia y diversidad del virus Y de la papa (PVY) en los cultivos de papa para semilla en los Estados Unidos (EU), se identificó a una variante inusual a niveles bajos pero significativos en múltiples estados. Esta variante, PVY O -O5, se detectó inicialmente con un anticuerpo monoclonal comercialmente disponible específico para PVY N , el 1F5. Este anticuerpo es ampliamente usado por los Programas de Certificación de Semilla en los EU para PVY N , y es uno de los dos anticuerpos designados por la Organización Norteamericana de Protección de Plantas (NAPPO) para pruebas de pre-envío de lotes de tubérculos que serán transportados entre países. Consecuentemente, los PVY N positivos identificados con el anticuerpo 1F5 han disparado acciones cuarentenarias, evitando envíos trans-fronteras y han impactado al comercio. Aquí, nosotros demostramos con diversos métodos que PVY O -O5 es una variante del PVY ordinario (PVY O ). Específicamente, la variante PVY O -O5 es probable que haya surgido debido a una substitución de un aminoácido dentro de la proteína de la cápside. Esta variante no induce necrosis de las venas en tabaco o necrosis del A. V. Karasev : O. V. Nikolaeva : X. Hu : Z. Sielaff : tubérculo en variedades susceptibles de papa. Aún mas, se le identifica c...

Potato virus Y: An Evolving Concern for Potato Crops in the United States and Canada

“…The PVY O -O5 variant accounted for 6 and 3% of the total isolates from the United States and Canada, respectively. This variant was found in several areas of the United States, but was concentrated in one state (42). The distribution in Canada is unknown.…”

“…A cocktail of biological, serological, and/or molecular diagnostic tests are required, at considerable labor and expense, to effectively classify these strains (51). Inaccurate field inspections and improper diagnosis have contributed to some unnecessary trade restrictions (42 N-Wi would have tested negative and would not have been eliminated as a seed source unless the overall PVY incidence was above tolerance limits. This could have perpetuated the PVY N-Wi strain and increased its distribution.…”

Serological detection of bacterial pathogens associated with rotted potato tubers

“…Karasev et al (2011) studied serologically, the genetic diversity of the ordinary strain of Potato virus Y (PVY) and origin of recombinant PVY strains. Serological properties of ordinary and necrotic isolates of PVY were taken into account to survey the occurrence for both isolates in the U.S seed crop (Karasev et al, 2010). Baldauf et al (2006) worked on biological and serological properties of Potato Virus Y isolates in Northeastern United States potato in New York.…”

Recombinants of PVY Strains Predominate Among Isolates from Potato Crop in Poland

“…The occurrence of biologically diverse isolates with their highly homologous genomes brings into question the exact nature of gene structure in relation to function (Barker et al 2009). Point mutation has been shown to be responsible for serotype variation of certain isolates (Chikh Ali et al 2007;Karasev et al 2010). For the recombinant PVY NTN isolate Gr99, two amino acid changes in the viral genetic determinants (K-400 to R-400, E-419 to D-419 in the HC-Pro protein) may be responsible for the loss of VN in tobacco (Hu et al 2009b).…”