Potato Tuber Necrotic Ringspot Research Articles

Antagonism and Synergism Characterize the Interactions between Four North American Potato Virus Y Strains

Potato virus Y (PVY) is one of the most important constraints to potato production worldwide. There is an increasing occurrence of recombinant PVY strains PVYNTN and PVYN-Wi and a decline in the incidence of the nonrecombinant PVYO. We hypothesized that this may be due to the ability of these recombinant strains to antagonize and/or outcompete PVYO in mixed infections. To determine this, we investigated interactions between PVYO and three recombinant PVY strains common in North America: PVYNTN, PVYN-Wi, and PVYN:O. Overall, our study showed that these interactions are tissue-dependent. Specifically, PVYNTN, the main causal agent of potato tuber necrotic ringspot disease (PTNRD), was found to be more adaptable than PVYO, especially in potato leaves due, at least in part, to the Ny gene that confers hypersensitive resistance (HR) to PVYO. Furthermore, PVYN-Wi was found to repress PVYO in potato tubers but act synergistically in potato leaves. The PVYO-induced foliage necrosis in cultivar ‘Ranger Russet’ was observed to be more severe in plants co-infected by PVYN-Wi and PVYN:O, respectively, resulting in plant death. Strikingly, this PVYO -induced necrosis was suppressed by PVYNTN in doubly infected plants. These interactions may, at least partially, explain the decreasing incidence of PVYO in United States potato production regions, especially given that many cultivars contain the Ny gene, which likely limits PVYO enabling PVYNTN and PVYN-Wi to outcompete. We also found that replication and cell-to-cell movement of these PVY strains in tubers at 4 °C was similar to levels at ambient temperature.

Management of Potato virus Y (PVY–NTN) causing potato tuber necrotic ringspot disease (PTNRD) in potato by prior treatment with a mild PVY strain

Management of Potato virus Y (PVY–NTN) causing potato tuber necrotic ringspot disease (PTNRD) in potato by prior treatment with a mild PVY strain

Prevalence of Recombinant Strains of Potato Virus Y in Seed Potato Planted in Idaho and Washington States Between 2011 and 2021.

Potato virus Y (PVY) has emerged as the main reason for potato seed lot rejections, seriously affecting seed potato production in the United States throughout the past 20 years. The dynamics of PVY strain abundance and composition in various potato growing areas of the United States has not been well documented or understood up to now. The objective of this study was to find out the prevalence of PVY strains in potato fields in the Pacific Northwest (PNW), including seed potato production systems in the State of Idaho and commercial potato fields in the Columbia Basin of Washington State between 2011 and 2021. Based on the testing of >10,000 foliar samples during Idaho seed certification winter grow-out evaluations of seed potato lots and seed lot trials in Washington State, a dramatic shift in the PVY strain composition was revealed in the PNW between 2011 and 2016. During this time period, the prevalence of the ordinary, PVYO strain in seed potato dropped 8- to 10-fold, concomitantly with the rise of recombinant strains PVYN-Wi and PVYNTNa, which together accounted for 98% of all PVY positives by 2021. In Idaho seed potato, PVYNTNa strain associated with the potato tuber necrotic ringspot disease (PTNRD) was found to increase threefold between 2011 and 2019, accounting for 24% of all PVY positives in 2019. Mild foliar symptoms induced by recombinant PVY strains may be partially responsible for the proliferation of PVYN-Wi and PVYNTNa in potato crops. A spike of another PTNRD-associated recombinant, PVY-NE11, was recorded in the PNW between 2012 and 2016, but after reaching a 7 to 10% level in 2012 to 2013 this recombinant disappeared from the PNW potato by 2019. Whole genome sequence analysis of the PVY-NE11 suggested this recombinant was introduced in the United States at least three times. The data on PVY strain abundance in the PNW potato crops suggest that virus management strategies must consider the current dominance of the two recombinant PVY strains, PVYN-Wi and PVYNTNa.

Molecular and Biological Characterization of Recombinant Isolates of Potato virus Y Circulating in Potato Fields in Mexico.

Potato virus Y (PVY) is a significant threat to potato (Solanum tuberosum) production in Mexico. The presence of recombinant strains of PVY circulating in potato has been reported in the country, but no systematic study on the genetic diversity of PVY in potato and prevalence of PVY strains has been conducted yet. We report on a series of surveys in seed potato production areas in two states in Mexico, namely, Chihuahua and Jalisco, between 2011 and 2019. PVY was detected through the period of nine years in multiple potato cultivars in both states, often remaining asymptomatic in the most popular cultivars, such as 'Fianna' and 'Agata'. When typed to strain, all PVY samples studied were found to have N-serotype, and were all identified molecularly as isolates of the same recombinant strain, PVYNTN. Five of these PVY isolates were tested on tobacco (Nicotiana tabacum), where they induced vein necrosis supporting the molecular typing. This identification was also confirmed biologically on differential potato cultivars, where one PVYNTN isolate from the 2013 survey triggered the hypersensitive resistance conferred by the Nztbr gene in the cv. Maris Bard. Seven of these Mexican PVYNTN isolates, collected between 2013 and 2019, including two PVY isolates from potato tubers exhibiting potato tuber necrotic ringspot disease, were subjected to whole genome sequencing and found to show a typical PVYNTNa recombinant structure. When subjected to phylogenetic analysis, Mexican PVYNTN sequences clustered in more than three separate clades, suggesting multiple introductions of PVYNTN in the country. The wide circulation of the PVYNTN strain in Mexican potato should be considered by potato producers, to develop mitigation strategies for this PVY strain associated with tuber necrotic symptoms.

Global Plant Virus Disease Pandemics and Epidemics.

The world’s staple food crops, and other food crops that optimize human nutrition, suffer from global virus disease pandemics and epidemics that greatly diminish their yields and/or produce quality. This situation is becoming increasingly serious because of the human population’s growing food requirements and increasing difficulties in managing virus diseases effectively arising from global warming. This review provides historical and recent information about virus disease pandemics and major epidemics that originated within different world regions, spread to other continents, and now have very wide distributions. Because they threaten food security, all are cause for considerable concern for humanity. The pandemic disease examples described are six (maize lethal necrosis, rice tungro, sweet potato virus, banana bunchy top, citrus tristeza, plum pox). The major epidemic disease examples described are seven (wheat yellow dwarf, wheat streak mosaic, potato tuber necrotic ringspot, faba bean necrotic yellows, pepino mosaic, tomato brown rugose fruit, and cucumber green mottle mosaic). Most examples involve long-distance virus dispersal, albeit inadvertent, by international trade in seed or planting material. With every example, the factors responsible for its development, geographical distribution and global importance are explained. Finally, an overall explanation is given of how to manage global virus disease pandemics and epidemics effectively.

Effects of the Age-Related Resistance to Potato virus Y in Potato on the Systemic Spread of the Virus, Incidence of the Potato Tuber Necrotic Ringspot Disease, Tuber Yield, and Translocation Rates Into Progeny Tubers.

The recombinant strain of potato virus Y (PVY), PVYNTN, is the main cause of the potato tuber necrotic ringspot disease (PTNRD) in susceptible potato cultivars, which reduces the quality of potato tubers, in addition to the yield loss. Control of PVY has been the main challenge in most potato-producing areas. Here, the effects of the age-related resistance (ARR) were investigated in transplants of a potato cultivar Yukon Gold to the infection with PVYNTN strain in greenhouse experiments. Within the first 3 weeks after transplanting into soil (week 1 [W1] to W3), Yukon Gold plants developed ARR that impaired the systemic movement of PVYNTN into upper noninoculated leaves and concomitant translocation into progeny tubers starting from W4 after transplanting. The yield and quality of tubers from PVY-infected plants with the established ARR (W5 to W8) were comparable with the healthy controls, suggesting that late PVY infection would not significantly affect commercial potato production. Plants inoculated early (W1 to W2), before the establishment of the ARR, exhibited a 100% primary systemic infection with PVYNTN and produced fewer tubers of smaller sizes, exhibiting PTNRD; this resulted ≤70% yield reduction compared with plants inoculated later in the season (W5 to W8). This ARR greatly restricted the systemic movement of PVYNTN in the foliage and resulted in very limited translocation rates of the virus into tested progeny tubers: 7.8 and 4.1% in 2017 and 2018, respectively, of all plants inoculated later in the season (W5 to W8). This study suggests that PVYNTN management programs in Yukon Gold seed potato should focus more on the early stages of the potato development before the onset of the ARR.

Genetic Diversity of Potato virus Y in Potato Production Areas in Northeast China

In 2011-2014, ELISA or nucleic acid spot hybridization (NASH) testing for common potato viruses or Potato spindle tuber viroid (PSTVd) was performed on 500 leaf samples collected in potato fields in the northeast provinces Heilongjiang and Inner Mongolia, China. The results revealed that 38.4% (Heilongjiang) and 27.7% (Inner Mongolia) were positive for Potato virus Y (PVY). To unveil the strain composition and population structure of PVY in the region, the multiplex RT-PCR described by Chikh-Ali et al. was performed on all of the ELISA-PVY-positive samples. Of the 158 samples whose PVY strain scenarios could be determined, PVYNTN-NW-SYR-II and PVYN-Wi were the most abundant strains, occurring in 58.9 and 47.5% samples, followed by PVYNTN-NW-SYR-I (31.0%), PVYN:O (19.6%), Eu-PVYNTN (7.6%), NA-PVYN (1.3%), and PVYO (0.6%). In the 84 single-strain-infected samples, PVYN-Wi accounted for 41.7%, PVYNTN-NW-SYR-II for 40.5%, PVYNTN-NW-SYR-I for 14.3%, and PVYN:O and Eu-PVYNTN for 3.6% each. Seven isolates representing PVYNTN-NW-SYR-I (HLJ-6-1 and HLJ-9-4), PVYNTN-NW-SYR-II (INM-W-369-12 and SC-1-1-2), PVYN:O (HLJ-30-2), and PVYN-Wi (HLJ-BDH-2 and HLJ-C-429) were sequenced and analyzed molecularly. Whereas the sequence identities for isolates belonging to the same strain group were >98.5%, they fell for isolates belonging to different strain groups to 92.7-98.1% at the genome level and 96.1-98.4% at the polyprotein level. Interestingly, the exact location of the recombination events varied among isolates within a strain group. Phylogenetic analysis of all 42 full length PVY sequences from China indicated that most clustered to various recombinant groups, despite the fact that the PVY isolates were isolated from at least five host species. Pathological analysis of four isolates representing PVYN:O, PVYN-Wi, PVYNTN-NW-SYR-I, and PVYNTN-NW-SYR-II revealed that the PVYNTN-NW-SYR-II isolate incited the most severe symptoms on potato cultivar Kexin 13, followed by PVYNTN-NW-SYR-I, PVYN:O and PVYN-Wi. The PVYNTN-NW-SYR-I and PVYNTN-NW-SYR-II isolates also caused necrotic ringspots on the tubers of Kexin 13, indicating their ability to induce the potato tuber necrotic ringspot disease in potato.

Occurrence of Diverse Recombinant Strains of Potato virus Y Circulating in Potato Fields in Egypt.

Potato is one of the staple crops in Egypt, grown under irrigation almost continuously year-round. Potato virus Y (PVY) has been reported as one of the main viruses affecting potatoes in Egypt, but limited information is available on PVY strains circulating in potato fields in the country. From 2014 to 2016, virus surveys were conducted in several potato-growing governorates of Egypt, and PVY-positive samples were found to represent at least five distinct recombinant PVY strains, including PVYNTN and PVYN-Wi. Whole genome sequences were determined for four isolates representing strains PVY-SYR-III (Egypt7), PVY-261-4 (Egypt11), PVYNTNa (Egypt35), and a novel recombinant named Egypt24 that combined molecular properties of strains PVY-261-4 and PVY-Wilga156var. At least three recombinants found in Egypt in potato were previously found associated with potato tuber necrotic ringspot disease (PTNRD). The identification of multiple recombinant types of PVY in potato in Egypt, including the novel recombinant Egypt24, suggests a wide presence of PTNRD-inducing virus strains in the country.

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

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.

Molecular characterization of potato virus y inducing potato tuber necrotic ringspot disease in Serbia

The Potato virus Y (PVY) is the most important limiting factor for potato seed production in Serbia. Currently, PVY is a major concern for the potato seed growers. Initially, serological (ELISA) tests were carried out on 100 potato seed tubers from each of the seven potato cv. during 2013. The infection rates with the PVYN was between 5 and 36%. A complete genome sequencing of the most common Serbian isolate of PVY (3D), followed by molecular characterization and phylogenetic analysis has been performed to show what group it belongs to. Our isolate?s complete genome sequence (KJ946936) showed that the Serbian PVY isolate (3D) is 99.7% identical at nt level, with other tuber necrosis strain group (PVYNTN) from Europe. Phylogenetic analysis revealed three consistent lineages of isolates, showing that our isolate was clustered with the isolates from Europe and North America in the PVYN lineage which induces potato tuber necrotic ringspot disease (PTNRD). The Serbian isolate of PVYNTN together with the isolates from Europe was clustered in the branch of European sublineage, with a high bootstrap support and no genetic diversity. This is the first study in Serbia demonstrating phylogenetic distinction between our isolate and other isolates of PVY.

Occurrence and Molecular Characterization of Recombinant Potato virus YNTN Isolates from Sulawesi, Indonesia.

The importance of potato has increased dramatically in Indonesia over the last three decades. During this period, 'Granola', a potato cultivar originally from Germany, has become the most common cultivar for fresh consumption in Indonesia. In August 2014, a survey was conducted in Sulawesi, where potato fields cultivated with Granola and its selection, 'Super John', were sampled for Potato virus Y (PVY) presence. PVY was found in Sulawesi for the first time. Samples determined to be positive for PVY were subsequently typed to strain using reverse-transcription polymerase chain reaction assays. All PVY isolates sampled were identified as PVYNTN recombinants, with three recombination junctions in P3, VPg, and CP regions of the genome. Three local PVY isolates were subjected to whole-genome sequencing and subsequent sequence analysis. The whole genomes of the Indonesian PVYNTN isolates I-6, I-16, and I-17 were found to be closely related to the European PVYNTN-A. This recombinant type was shown previously to cause potato tuber necrotic ringspot disease (PTNRD) in susceptible potato cultivars. The dependence of potato farmers on mostly a single cultivar, Granola, may have given a competitive advantage to PVYNTN over other PVY strains, resulting in the predominance of the PVYNTN recombinant. The dominance of PVYNTN in Sulawesi, and possibly in Indonesia as a whole, represents a potential risk to any newly introduced potato cultivar to the country, especially cultivars susceptible to PTNRD.

Molecular Characterization of Recombinant Strains of Potato virus Y From Saudi Arabia.

Potato virus Y (PVY) exists as a complex of strains, many of which are recombinants. The practical importance of PVY recombinant strains has increased due to their ability to induce potato tuber necrotic ring spot disease (PTNRD) that seriously affects tuber quality. In Saudi Arabia, potato production has increased fivefold during the last three decades, reaching 460,000 tons per year. Although PVY has been reported as one of the main viruses affecting potatoes, no information is available on PVY strains circulating in the country. In August 2014, a survey was conducted in a seed potato field at Al-Jouf, Saudi Arabia. PVY-positive samples selected based on visual symptoms and serological reactivity were subjected to strain typing using multiplex RT-PCR assays and were determined to represent recombinant PVY strains. Whole genome sequences were determined for two representative isolates, S2 and S9, through direct sequencing of a series of overlapping RT-PCR fragments for each isolate, and found to represent strains PVY-NE11 and PVYZ (SYR-III), respectively. One of the recombinant types, SYR-III, was previously found in nearby Syria and Jordan, but the second recombinant, PVY-NE11, was found before only in the United States. Both recombinants, PVY-NE11 and SYR-III, were previously found associated with PTNRD and thought to be rare. The current identification of PVY-NE11 and SYR-III in seed potato in a new geographic region suggests that these recombinants may not be as rare as previously believed. This is the first report on the occurrence of recombinant strains of PVY in potato in Saudi Arabia, and the first report on the PVY-NE11 strain of PVY found in potato outside of the United States.

First report of potato tuber necrotic ringspot disease associated with PVY recombinant strains in Ireland

Potato tuber necrotic ringspot disease (PTNRD) as described by Kus et al., (1992) is found worldwide but has not previously been identified in Ireland. In recent years necrotic symptoms, veinal necrosis, spots, mottling, mosaics and…

First Report of Recombinant Potato virus Y Strains in Potato in Jalisco, Mexico.

Potato virus Y (PVY) is a serious problem for potato production worldwide. The virus reduces both tuber yield and quality, and recent spread of recombinant strains of PVY in potato production areas is largely credited with the spread of potato tuber necrotic ringspot disease (PTNRD) (1). In Mexico, recombinant strains of PVY were reported in at least two states, Chihuahua (4) and the State of Mexico (3); however, no surveys have been conducted in other potato-producing areas, and the spectrum of PVY isolates circulating in the country has remained uncharacterized. In October 2011, a small-scale survey of seed potato was conducted in the state of Jalisco, Mexico, to identify PVY isolates present in fields. Twelve seed potato fields were inspected visually. These represented various generations of seed potato, from nuclear to G2. Leaf samples were collected from plants displaying mosaic, crinkling, and yellowing symptoms, and were tested for PVY. Fifty samples were collected from cultivars Fabula, Mondial, Fianna, Gigant, Caesar, and Adora. Of the 50 leaf samples collected, seven were PVY-positive using the Immuno-strip Kit (Agdia, Elkhart, IN), and six of these were determined to have a N-serotype according to the typing by the Pocket Diagnostics lateral flow kit (Forsite Diagnostics, Ltd., York, UK). PVY-positive samples came from cultivars Fabula (2 with N serotype), Mondial (4 with N serotype), and Fianna (1 with O serotype). Extracts of the seven PVY-positive leaf samples were applied to Whatman FTA cards (Sigma, St. Louis, MO), dried, and transported to the Plant Virology Laboratory at the University of Idaho for further characterization. All samples immobilized on FTA cards were subjected to RNA extraction and standard reverse transcriptase (RT)-PCR typing using a set of PVY-specific primers (2) to determine the strain type. All PVY isolates were recombinant. The six N-serotype samples were found to contain recombinant PVYNTN isolates and produced characteristic bands of 181 and 452 bp in RT-PCR, which indicated the presence of two recombination junctions in the HC-Pro/P3 and VPg regions typical of European PVYNTN isolates. The one O-serotype sample was identified as a recombinant PVYN-Wi/N:O isolate, and produced 181 and 689 bp bands in RT-PCR, which indicated the presence of one recombination junction in the HC-Pro/P3 region. Sequence analysis of RT-PCR products amplified from five samples with N serotype identified them as PVYNTN isolates, and from the one with O serotype identified it as PVYN-Wi/N:O isolate. Sequence comparisons confirmed that N serotype samples contained PVY isolates most closely related to typical PVYNTN sequences (Accession No. EF026075), while the O serotype sample contained the PVY isolate most closely related to PVYN-Wi from Europe (HE608963). The data obtained suggest the presence of two different types of PVY recombinants, PVYNTN and PVYN-Wi, in seed potato in Jalisco. Additional surveillance for these recombinant isolates may be needed, as well as a survey of their effects on tuber quality in production areas. This is the first report of recombinant isolates of PVY often associated with PTNRD circulating in seed potato in Jalisco, Mexico.

Assessment of SNaPshot and single step RT-qPCR methods for discriminating Potato virus Y (PVY) subgroups

Potato virus Y (PVY) is the most important virus infecting potato (Solanum tuberosum), causing potato tuber necrotic ringspot disease (PTNRD), with a great impact on seed potato production. Numerous PVY strain groups with different pathogenicity and economical impact are distributed worldwide. Tools for accurate and reliable detection and discrimination of PVY strain groups are therefore essential for successful disease management.Two state of the art characterization tools based on detecting molecular markers – RT-qPCR (Kogovsek et al., 2008) and SNaPshot (Rolland et al., 2008) – were assessed for their ability to assign PVY accurately to the correct group. The results were validated by bioassay, ELISA and in silico sequence analysis. The spectrum of PVY strain groups distinguished by SNaPshot is broader than that by RT-qPCR. However, the latter was more reliable in discriminating the PVYNTN group members, known for their ability to induce PTNRD on selected potato cultivars. The difference in discrimination precision was due to different molecular markers being targeted by RT-qPCR and SNaPshot. Both tools use genotypic markers for detecting PVYNTN strain groups. Future development, however, should be focused on identifying the genomic determinants of the tuber necrosis property. Until then, the RT-qPCR and SNaPshot methods remain the most powerful diagnostic tools for detecting the PVY subgroup isolates found in Europe.

Occurrence of Potato virus Y strain PVYNTN in foundation seed potatoes in Japan, and screening for symptoms in Japanese potato cultivars

In 2008 and 2009 seasons, a sudden increase in Potato virus Y (PVY) incidence was recorded in foundation seed potatoes in Hokkaido, northern Japan. This increase was obvious during the field inspection and the postharvest indexing. Molecular typing revealed that besides the previously reported strains of PVYO and PVYNA‐N, the most common strain identified was the recombinant PVYNTN, with three characteristic recombinant junctions at the HC‐Pro, VPg and CP regions. No potato tuber necrotic ringspot disease (PTNRD) was observed in foundation seed potatoes in correlation with the presence of PVYNTN. Moreover, an isolate with a typical PVYNTN recombinant genome, namely Eu‐12Jp, did not induce PTNRD in 62 Japanese potato cultivars tested in both primarily and secondarily infected plants. Two cultivars carrying the extreme resistance gene Rychc were resistant to the infection with Eu‐12Jp, which presents potential sources of resistance to PVYNTN. Eu‐12Jp induced systemic mottle in potato cultivars Desiree and King Edward carrying resistance genes Ny and Nc, respectively, but induced a hypersensitive reaction in potato cultivar Maris Bard, with the Nz hypothetical resistance gene typical of the PVYZ strain group. Therefore, based on the genome structure and the reaction of the potato N resistance genes, Eu‐12Jp should be classified as PVYZ‐NTN, as described for isolates from Idaho, USA recently. This is the first report of PVYZ‐NTN in Japan and the sudden and increased occurrence of PVYNTN/PVYZ‐NTN represents a potential risk of PTNRD developing and increases the significance of PVY in Japan.

Incidence of virus Y Strains and Effect of Infection on the Productivity of Potato Tubers.

Field survey studies were conducted during three growing seasons to study the prevalence and distribution of PVY strains infecting potato in different locations at Behairah, Sharkia and Menoufia governorates (Egypt). The most common symptoms were different types of mosaic, leaf crinkling, necrosis and leaf drop streak. Four virus strains namely: tobacco veinal necrosis strain (PVY), common strain (PVY), stipple streak strain (PVY) and potato tuber necrotic ring spot (PVY) were detected using DAS-ELISA. At the nile growing season PVY was the most prevalent virus (63.5%) followed by PVY (25%). PVY had the highest frequency (67%), followed by PVY (25.7%) at the winter growing season. While at summer growing season, PVY and PVY had the most prevalent viruses (36.7%). Agar double diffusion test was used to confirm the identity of the isolated PVY strains. The Egyptian PVY strains reacted strongly with the specific antiserum for each strain forming a prominent precipitin line. Productivity of potato cultivar Spunta to infect with virus strains was conducted in the farm of Benha, Qalubia decreased by 22.6% to 50.5% according to the strain as compared with control.

Recent Advances on Potato virus Y Research in Canada

Significant progress has been made in recent years in understanding pathological, serological and molecular properties of various strains of PVY and the aphid-mediated transmission. PVYO and PVYN appear to be the basic strain groups. Through genome recombination between these two groups, progeny groups whose genome possess one (e.g., PVYN:O or PVYN-Wi) to three (e.g., recombinant PVYNTN or European-PVYNTN) recombinant joints of PVYO and PVYN emerged. PVYN:O causes PVYN-like veinal necrosis in tobacco, but reacts to PVYO-specific antibody. PVYNTN causes potato tuber necrotic ringspot diseases in sensitive potato cultivars, and PVYN-like necrosis in tobacco plants, and reacts to PVYN-specific antibody. Through single nucleotide mutation(s), non-recombinant PVYNTN (or North American PVYNTN) also emerged from PVYN. It is also noteworthy that PVYN isolates originated from North America and Europe may have evolved separately; and to date most recombinant strains appear to be progenies of Eu-PVYN and PVYO. Several RT-PCR-based methodologies have been developed to characterize and detect various strains of PVY. A field survey revealed that PVYN:O has become a predominant strain in Manitoba and neighbouring states in USA. Moreover, three distinct variant groups inciting severe, intermediate and mild veinal/petiole/stem necrosis, respectively, on tobacco plants were observed within the PVYN:O isolates collected in Manitoba. Pathological and molecular diversity within PVYO strain group were revealed in New Brunswick, represented by PVYO-FL as a severe variant and by PVYO-RB as a mild variant. Studies on the transmission of PVY by various species of aphids revealed that aphid behavior plays an important role in the vector-mediated transmission. Application of mineral oil on the growing crop, especially in combination with use of crop borders, reduces aphid-mediated PVY transmission. Based on recent PVY research studies, Bartlett Superior 70 Oil was approved in 2011 for application to potato crops in Canada.

Epitope Mapping for Monoclonal Antibodies Recognizing Tuber Necrotic Isolates of Potato Virus Y

Potato virus Y (PVY) is an important viral pathogen of potato responsible for reducing tuber yield and quality across the globe. The PVYN and PVYNTN strains, the latter of which induces potato tuber necrotic ringspot disease (PTNRD), are regulated for international potato trade, and have been routinely detected using monoclonal antibodies (MAbs) that discriminate between PVYN and PVYO serotypes. Here, we identify the distinct binding sites in the capsid protein of PVY for three of the four main PVYN-specific MAbs, Bioreba-N, SASA-N, and Neogen-N, available commercially. These binding domains were mapped through a combination of TAS-ELISA testing of MAbs on multiple reference isolates of PVY, sequence analysis, heterologous expression of capsid protein fragments, and synthetic peptide binding experiments. All three MAbs were found to bind linear epitopes located within the first 31 N-terminal amino acids of the capsid protein. Bioreba-N MAb epitope spanned aa 1-17 and included three positions, aa 1, aa 11, and aa 17, which differ between PVYN and PVYO serotypes. Both SASA-N and Neogen-N epitopes spanned aa 22-30, and included two positions, aa 24 and aa 29, which differ between PVYN and PVYO serotypes. Epitopes for SASA-N and Neogen-N MAbs are likely to be identical or overlapping. Examination of available sequences for tuber necrotic isolates of PVY that do not react with PVYN-specific MAbs SASA-N and Neogen-N indicated possible selection for substitutions in corresponding epitopes leading to the loss of reactivity towards these antibodies. The data obtained suggested that testing with more than one PVYN serotype-specific MAb could assure a reliable serological identification of a PVYN or PVYNTN isolate.

An infectious full-length cDNA clone of potato virus YNTN-NW, a recently reported strain of PVY that causes potato tuber necrotic ringspot disease

A full-length infectious cDNA clone of potato virus Y (PVY) was constructed based on an isolate of the PVY(NTN-NW) strain, SYR-II-2-8, which is able to cause potato tuber necrotic ringspot disease (PTNRD). Silent point mutations were introduced to modify sequences similar to the prokaryotic promoter elements detected at the 5' terminus of the P3 coding region of SYR-II-2-8. This, along with modification of the growing conditions of E. coli, led to the successful construction of a stable full-length infectious cDNA clone, named p2-8C3. The biological properties of p2-8C3 were identical to those of SYR-II-2-8, both of which induced PTNRD in potato, veinal necrosis in tobacco, and similar symptoms in the potato cultivars inoculated.