RFLP mapping of the whole genome of ten viral isolates representative of different biological groups of potato virus Y

Genetic Diversity of Nine Non-Recombinant Potato virus Y Isolates From Three Biological Strain Groups: Historical and Geographical Insights

Potato virus Y (PVY) isolates from potato currently exist as a complex of six biologically defined strain groups all containing nonrecombinant isolates and at least 14 recombinant minor phylogroups. Recent studies on eight historical UK potato PVY isolates preserved since 1984 found only nonrecombinants. Here, four of five PVY isolates from cultivated potato or wild Solanum spp. collected recently in Australia, Mexico, and the U.S.A. were typed by inoculation to tobacco plants and/or serological testing using monoclonal antibodies. Next, these five modern isolates and four additional historical UK isolates belonging to biological strain groups PVY^C, PVY^Z, or PVY^N obtained from cultivated potato in 1943 to 1984 were sequenced. None of the nine complete PVY genomes obtained were recombinants. Phylogenetic analysis revealed that the four historical UK isolates were in minor phylogroups PVY^C1 (Y^C-R), PVY^O-O (Y^Z-CM1), PVY^NA-N (Y^N-M), or PVY^Eu-N (Y^N-RM), Australian isolate Y^O-BL2 was in minor phylogroup PVY^O-O5, and both Mexican isolate Y^N-Mex43 and U.S.A. isolates Y^N-MT12_Oth288, Y^N-MT12_Oth295, and Y^N-WWAA150131G42 were in minor phylogroup PVY^Eu-N. When combined, these new findings and those from the eight historical UK isolates sequenced earlier provide important historical insights concerning the diversity of early PVY populations in Europe and the appearance of recombinants in that part of the world. They and four recent Australian isolates sequenced earlier also provide geographical insights about the geographical distribution and diversity of PVY populations in Australia and North America.

Detection and Quantification of Potato virus Y Genomes in Single Aphid Stylets

Typically, the detection of a plant virus within its vector is carried out on the entire insect body. This process can be a possible source of confusion in the quantification of transmissible virus particles for styletborne viruses such as Potato virus Y (PVY), since the transmissible virus fraction is the one only retained in the aphid vector's mouthparts. The objective of this study was to develop and validate the quantitative PCR method for the detection and quantification of PVY in the vector's stylet. Using a specific method based on TaqMan chemistry with higher sensitivity than conventional reverse transcription PCR, this study reveals that a significant amount of the virus is enclosed within the dissected stylets of Myzus persicae. Because this quantification only concerns the portion of the virus attached to the stylets, uniformity was observed in the recorded numbers of virus targets. This novel assay is applicable to several PVY strains as a rapid and sensitive detection method for use in PVY research and offers a convenient tool for deciphering the mechanism of Potyvirus acquisition.

A complex eIF4E locus impacts the durability of va resistance to Potato virus Y in tobacco

Many recessive resistances against potyviruses are mediated by eukaryotic translation initiation factor 4E (eIF4E). In tobacco, the va resistance gene commonly used to control Potato virus Y (PVY) corresponds to a large deletion affecting the eIF4E-1 gene on chromosome 21. Here, we compared the resistance durability conferred by various types of mutations affecting eIF4E-1 (deletions of various sizes, frameshift or nonsense mutations). The 'large deletion' genotypes displayed the broadest and most durable resistance, whereas frameshift and nonsense mutants displayed a less durable resistance, with rapid and frequent apparition of resistance-breaking variants. In addition, genetic and transcriptomic analyses revealed that resistance durability is strongly impacted by a complex genetic locus on chromosome 14, which contains three other eIF4E genes. One of these, eIF4E-3, is rearranged as a hybrid gene between eIF4E-2 and eIF4E-3 (eIF4E-2-3 ) in the genotypes showing the most durable resistance, while eIF4E-2 is differentially expressed between the tested varieties. RNA-seq and quantitative reverse transcriptase-polymerase chain reaction experiments demonstrated that eIF4E-2 expression level is positively correlated with resistance durability. These results suggest that besides the nature of the mutation affecting eIF4E-1, three factors linked with a complex locus may potentially impact va durability: loss of an integral eIF4E-3, presence of eIF4E-2-3 and overexpression of eIF4E-2. This latter gene might act as a decoy in a non-productive virus-plant interaction, limiting the ability of PVY to evolve towards resistance breaking. Taken together, these results show that va resistance durability can in large part be explained by complex redundancy effects in the eIF4E gene family.

The amino acid 419 in HC-Pro is involved in the ability of PVY isolate N605 to induce necrotic symptoms on potato tubers

The ability to induce the potato tuber necrosis ringspot disease (PTNRD) is a property shared by PVY isolates belonging to different groups (e.g. PVY(N) and PVY(O)) and variants (e.g. PVY(NTN) and PVY(N)-W). The identification of viral molecular determinant(s) involved in the expression of PTNRD symptoms is essential for (i) an easier detection of tuber necrosis isolates and (ii) an improvement of our knowledge on the epidemiology of this potato disease. A reverse genetic approach associated with a biological typing of a collection of PVY chimeras and mutants indicated that residue E419 of the HC-Pro protein is linked to the ability of PVY to induce tuber necrosis on four PTNRD-susceptible potato cultivars. Indeed, the substitution of the N-type glutamic acid (E) in O-type aspartic acid (D) at position 419 in the HC-Pro cistron prevents the expression of tuber necrosis on infected tubers without reducing the virulence of the corresponding E/D419 mutant. This result opens opportunities for the future studies on potato/PVY interactions.

Molecular and Serological Typing of Potato virus Y Isolates from Brazil Reveals a Diverse Set of Recombinant Strains

In Brazil, Potato virus Y (PVY) currently presents a significant problem for potato production, reducing tuber yield and quality. Recombinant tuber necrotic isolates of PVY had been reported to occur in the country but no systematic study of the PVY isolate diversity was conducted thus far. Here, a panel of 36 PVY isolates, randomly collected in Brazil from potato between 1985 and 2009, was subjected to a systematic molecular and serological typing using reverse-transcription polymerase chain reaction and a series of PVY^O- and PVY^N-specific monoclonal antibodies. The data collected were combined with biological characterization of the same isolates in tobacco. Of the 36 isolates tested, 3 were typed as PVY^O, 10 as PVY^N:O/N-Wi, 21 as PVY^NTN, and 2 as "unusual" or inconclusive. Of the 10 isolates from the recombinant PVY^N:O/N-Wi strain group, 1 isolate, MAF-VOY, was found to have an unusual serological profile identical to the nonrecombinant PVY^O-O5 strain group. The 21 tested PVY^NTN isolates included 1 isolate that did not induce vein necrosis in tobacco and 2 isolates with an unusual serological profile (i.e., displaying negative reactivity to one commercial PVY^N-specific monoclonal antibody). Whole genome sequences were determined for four PVY isolates from Brazil, representing PVY^O, PVY^NTN, and PVY^N-Wi strains. The genome of the MAF-VOY isolate was found to be recombinant, having characteristic N-Wi structure with two recombinant junctions and carrying a single mutation in the capsid protein at position 98, which led to an unusual O5 serological reactivity. Taken together, the data obtained suggest that the two recombinant strains, PVY^NTN and PVY^N:O/N-Wi, now are apparently dominant in the Brazilian potato crop. The data also suggest that recombinant isolates in Brazil often have unusual serological reactivity which may hamper their correct identification by conventional typing based on enzyme-linked immunosorbent assay.

Identification of new Potato virus Y (PVY) molecular determinants for the induction of vein necrosis in tobacco

Two tobacco vein necrosis (TVN) determinants, the residues K(400) and E(419) , have been identified previously in the helper component-protease (HC-Pro) protein sequence of Potato virus Y (PVY). However, since their description, non-necrotic PVY isolates with both K(400) and E(419) necrotic determinants have been reported in the literature. This suggests the presence in the viral genome of other, as yet uncharacterized, TVN determinant(s). The identification of PVY(N) pathogenicity determinants was approached through the replacement of genomic regions of the necrotic PVY(N) -605 infectious clone by corresponding sequences from the non-necrotic PVY(O) -139 isolate. Series of PVY(N/O) chimeras and site-directed PVY mutants were constructed to test the involvement of different parts of the PVY genome (from nucleotide 421 to nucleotide 9629) in the induction of TVN symptoms. The analysis of both the genomic characteristics and biological properties of these mutants made it possible to highlight the involvement, in addition to residues K(400) and E(419), of the residue N(339) of the HC-Pro protein and two regions in the cytoplasmic inclusion (CI) protein to nuclear inclusion protein a-protease (NIa-Pro) sequence (nucleotides 5496-5932 and 6233-6444) in the induction of vein necrosis in tobacco infected by PVY isolates.

Modulation of Aphid Vector Activity by Potato virus Y on In Vitro Potato Plants

The effects of the infection of potato (Solanum tuberosum) plants by the nonpersistent Potato virus Y (PVY) were studied on the host plant colonization behavior of different colonizing (Myzus persicae) and noncolonizing (Aphis fabae, Brevicoryne brassicae, and Sitobion avenae) aphid species. The underlying questions of this study were to know how aphids respond when faced with PVY-infected plants and whether plant infection can modify the aphid behavior involved in PVY spread. Short-range orientation behavior was observed using a dual-choice set-up and aphid feeding behavior was monitored using the electrical penetration graph technique. None of the aphid species discriminated between healthy and PVY-infected plants. Nevertheless, most individuals of M. persicae landed on and probed only in one plant whereas noncolonizing aphid species exhibited interplant movements. Study of the aphid feeding behavior showed that PVY infection essentially modified phloem and xylem ingestion. M. persicae and S. avenae exhibited an increased duration of phloem phases on PVY-infected plants whereas A. fabae showed a decreased duration of phloem phases that benefited from an increased duration of xylem ingestion phases. None of these parameters were changed in B. brassicae. These data present evidence that aphids can respond to plants infected by nonpersistent viruses. Such behavioral modifications are discussed within the context of PVY spread in potato crops.

Discussion paper: The naming of Potato virus Y strains infecting potato

Potato virus Y (PVY) strain groups are based on host response and resistance gene interactions. The strain groups PVY(O), PVY(C) and PVY(N) are well established for the isolates infecting potato in the field. A switch in the emphasis from host response to nucleotide sequence differences in the virus genomes, detection of isolates recombining sequences of different strains, and the need to recognize isolates that cause necrotic symptoms in potato tubers have led to the assignment of new acronyms, especially to isolates of the PVY(N) strain group. This discussion paper proposes that any newly found isolates should be described within the context of the original strain groups based on the original methods of distinguishing strains (i.e., tobacco and potato assays involving use of 'differential' potato cultivars). Additionally, sequence characterization of the complete genomes of isolates is highly recommended. However, it is acceptable to amend the names of PVY isolates with additional, specific codes to show that the isolate differs at the molecular, serological or phenotypic level from the typical strains within a strain group. The new isolates should preferably not be named using geographical, cultivar, or place-association designations. Since many new variants of PVY are being discovered, any new static classification system will be meaningless for the time being. A more systematic investigation and characterization of PVY from potato at the biological and molecular levels should eventually result in a biologically meaningful genetic strain concept.

A multiple single nucleotide polymorphisms interrogation assay for reliable Potato virus Y group and variant characterization

The complex Potato virus Y classification, including groups (PVYN and PVYO) and variants (PVYNTN and PVYN-W), is based mainly on biological properties of isolates. Published PVY detection tools targeting markers not associated with biological properties could fail to assign correctly isolates in the current classification. To improve PVY detection tools, a single nucleotide polymorphism (SNaPshot) detection assay was developed. The technique was adapted to target the T/C9259, A/C2271, G/C8573 and A/G2213 PVY polymorphic nucleotides. The "TAGA", "CCCG", "CACA" and "CAGA" four-digit codes associated with tested samples allowed identification of PVYN, PVYO, PVYN-W and PVYNTN isolates, respectively. The PVY SNaPshot procedure is efficient and reliable for PVY detection and characterization in samples containing as few as 10(2) viral RNA copies. Moreover, PVY group assignment is possible for fractions containing only 10 copies of a PVY RNA genome. Finally, the SNaPshot assay allows PVY(N)/PVYO dual characterization for mixed samples containing PVYN/PVYO quantity ratios in the range of 0.1-10. This innovative SNaPshot tool improved clearly PVY diagnostic assays described previously by targeting simultaneously major functional markers and sequence unlinked to biological properties used separately in PVY detection tools available currently.

The Occurrence of PVYO, PVYN, and PVYN:O Strains of Potato virus Y in Certified Potato Seed Lot Trials in Washington and Oregon

Totals of 960 and 286 certified potato seed lots from locations across North America were planted in trials in Washington and Oregon, respectively, in 2001 to 2003 and tested for strains of Potato virus Y (PVY). The incidence of PVY^O-infected lots averaged 16.4 and 25.9% in the Washington and Oregon trials, respectively. There was a general trend of increasing incidence of the PVY^O, PVY^N:O, and PVY^N strains during this period, as evidenced by more infected cultivars, sites of seed origin, and number of seed growers providing infected seed lots. In particular, there was a dramatic increase in seed lots with the PVY^N:O strain from 2002 to 2003. PVY^N:O, in contrast to PVY^O, which only causes yield reduction, also causes internal and external damage to tubers, making them unmarketable. In 2003, PVY^N:O occurred in seed lots originating in eight states and three Canadian provinces. The increased incidence of PVY^N:O was likely due to the difficulty in differentiating this strain from PVY^O. The prevalence of PVY in potato seed lots documented herein poses a threat to potato production in the United States and suggests that current measures to reduce the incidence of this virus are inadequate.

Improvement of Potato virus Y (PVY) detection and quantitation using PVY(N)- and PVY(O)-specific real-time RT-PCR assays

A Potato virus Y (PVY) single nucleotide polymorphism (A/G(2213)), recently identified as a molecular determinant of the tobacco leaf necrosis symptom induced by PVY(N) isolates, has been used as a target to develop two PVY group-specific (PVY(N) and PVY(O)) fluorescent (TaqMan-based) real-time RT-PCR assays. These procedures allow detection, characterisation, and quantitation of a wide range of PVY isolates in samples containing 10(3)-10(8) viral transcripts. Moreover, the high specificity of these two new assays make the simultaneous detection and the reliable quantitation of PVY(N) and PVY(O) isolates in mixed solutions, regardless of the Y(N)/Y(O) ratio, feasible. The high sensitivity (threshold of 10(3) copies per reaction) and the PVY group specificity of these two new PVY detection tools clearly improve previously published PVY detection tests and offer new opportunities for PVY research programs.

Whole genome characterization of Potato virus Y isolates collected in the western USA and their comparison to isolates from Europe and Canada

Potato virus Y (PVY) is a serious potato pathogen that affects potato seed and commercial production crops. In recent decades, novel PVY strains have been described that cause necrotic symptoms on tobacco foliage and/or potato tubers. The major PVY strains that affect potato include PVY(O) and PVY(N), which have distinct serotypes that can be differentiated by immunoassay. Other economically important strain variants are derived from recombination events, including variants that cause tuber necrotic symptoms (PVY(NTN)) and PVY(O) serotypes that cause tobacco veinal necrosis (PVY(N)-W, PVY(N:O)). Although the PVY(NTN) and PVY(N)-W variants were first reported in Europe, apparently similar strains have been appearing in North America. Confirmation of the existence of these recombinant strains in North America is important, as is whether they spread from a common source or were derived by independent recombination. Whole genome sequencing can be used to positively identify strain variants and begin to address the issue of origins. Symptomology, serology, RT-PCR, and partial sequencing of the coat protein region were used to identify isolates of the PVY(NTN), PVY(N), PVY(NA-N), and PVY(N:O) for whole-genome sequencing. Sequencing confirmed the presence of PVY(NTN) and PVY(N) isolates that were >99% identical to European sequences deposited in GenBank in the 1990's. Sequences of the PVY(NA-N) and PVY(N:O) types were 99.0% and 99.5% identical to known sequences, respectively. There was no indication that recombinant strains PVY(NTN) or PVY(N:O) had different parental origins than recombinant strains previously sequenced. This is the first confirmation by whole-genome sequencing that "European"-type strain variants of PVY(N) and PVY(NTN) are present in North America, and the first reported full-length sequence of a tuber necrotic isolate of PVY(N:O).

Specific detection of the PVY(N)-W variant of Potato virus Y

PVY(N)-W is one of the variant populations of Potato virus Y (PVY). This variant is of concern in seed potato production and requires a specific diagnosis since it induces more or less symptomless infections and is not detectable easily in field inspections. Moreover, this variant is serologically indistinguishable from the common strain PVY(O). This study describes a simple and specific molecular detection test for the PVY(N)-W variant using a PCR protocol based on the recombinant point within the HC-Pro/P3 region of PVY(N) variants (PVY(NTN), PVY(N)-W). To avoid both detection of recombinant PVY(NTN) and PVY(N)-W isolates, a forward PVY(N)-like primer located in the HC-Pro region coupled to a reverse PVY(O)-like primer located in the NIa region was designed to amplify a specific PCR product of 4114 nt from PVY(N)-W isolates. This technique was assessed on 41 PVY reference and field isolates. Only isolates referenced as PVY(N)-W were amplified and gave the expected PCR product of 4114 nt, whereas no band was obtained from PVY(N), PVY(NTN) or PVY(O) isolates. In conclusion, this PVY(N)-W diagnosis tool is rapid, easy-to-use and suitable for large-scale testing in laboratories of seed potato certification.

A single nucleotide polymorphism-based technique for specific characterization of YO and YN isolates of Potato virus Y (PVY)

One of the most important properties used to classify Potato virus Y (PVY) isolates is their ability to induce (PVY(N)) or not (PVY(O)) veinal necrosis symptoms on the indicator host plant Nicotiana tabacum cv. Xanthi. As an alternative to biological assays, several serological and molecular detection tools have been developed for PVY detection and characterization and these have evolved as our knowledge of PVY has improved. However, the assays that have been previously published are all based on the use of neutral markers (antigenic determinants, sequence data, recombination sites or restriction enzyme cleavage sites), which are unlinked to the biological property being characterized (e.g. veinal necrosis). Using the recently identified molecular determinants of the tobacco leaf necrosis symptom induced by PVY(N) isolates, a one-step fluorescent [TaqMan] RT-PCR assay, based on a single nucleotide polymorphism (SNP) linked to the necrosis property of PVY isolates, has been designed. This assay reliably detects and distinguishes PVY(N) and PVY(O) isolates. The method is simple (leaf soak extraction process, gel-free, no post-PCR manipulations), rapid (96 tests in less than 3h from plants sampling to diagnostic results), sensitive (threshold in a range of 10(4)-10(5) PVY copies), reliable (correctly assigns 42 PVY isolates in their respective group) and allows co-detection of mixed samples containing close to equivalent PVY(N) and PVY(O) quantities. All these characteristics suggest that the newly developed SNP assay could be used to reliably classify PVY isolates, as a substitute for biological assays performed on N. tabacum cv. Xanthi.

Phylogenetic analysis of 5'-UTR and P1 protein of Indian common strain of potato virus Y reveals its possible introduction in India

The 5' untranslated region (UTR) and P1 region of the Indian strain of potato virus Y ordinary strain (PVYO) was cloned and sequenced for the first time. Database searches and multiple sequence alignment showed the highest sequence similarity with the PVYO strains of European origin. Based on the phylogenetic analysis and multiple sequence alignment, the possible evolution of PVYN from PVYO is predicted. PVYO strains from China and India were perhaps introduced into these countries from a similar geographical location. All major PVY strains available in the database can be classified into two major subgroups of North American and European origin. The Chinese and Indian PVYO strains fall within the European union subgroup suggesting a long association since potato was introduced from Europe into these countries by two separate independent events. The possible function of P1 protein in plant virus replication is suggested due to in-silico prediction of nuclear localization signal (NLS) and other phosphorylation regulatory domains at the vicinity of the NLS.

The detection of recombinant, tuber necrosing isolates of Potato virus Y (PVY(NTN)) using a three-primer PCR based in the coat protein gene

A simple and reliable procedure for reverse transcription-polymerase chain reaction (RT-PCR) detection and strain differentiation of Potato virus Y (PVY) was developed. Three primers were designed within the coat protein (CP) and nuclear inclusion protein b (NIb) region, exploiting a single base polymorphism identified as being present in all the recombinant PVY(NTN) isolates published. Samples infected with PVY produce a single band of 569 bp, while isolates belonging to PVY(NTN) strain give an additional band of 334 bp. The technique was tested on a collection of well-characterised isolates of PVY from a range of strains and was found to detect all of the isolates reported as belonging to the PVY(NTN) strain. All of the isolates detected possess a recombination event within the coat protein. Further sequence analysis revealed that all the recombinant PVY(NTN) isolates reported thus far would be detected using this assay, whilst isolates thought to be PVY(NTN) that do not possess the coat protein recombination event would not be detected.

Probable geographical grouping of PVY(N) and PVY(NTN) based on sequence variation in P1 and 5'-UTR of PVY genome and methods for differentiating North American PVY(NTN)

An increasing number of countries in recent years have reported the occurrence of potato tuber necrotic ringspot disease (PTNRD), caused by tobacco veinal necrosis strain of Potato virus Y (PVY(N)), belonging to the sub-group tuber necrosis (PVY(NTN)). Methods for the differentiation of PVY(NTN), based on primer sequences often detect isolates of European (EU) type but not the North American (NA) type. To resolve this problem, the nucleotide sequence of 5'-untranslated region (5'-UTR) and the P1 gene of 11 isolates of PVY(N) and PVY(NTN) from the European Union and North America was determined. Sequence comparison and phylogenetic analysis of 5'-UTR and P1 region indicated that PVY(N) isolates from the European Union and North America formed their own separate groups. Intra-group sequence identity for all except one was over 98%, as opposed to the inter-group identity of 90%. Additionally, the PVY(NTN) isolates from the European Union and North America clustered with their respective PVY(N) isolates. This indicates a possible evolution of PVY(NTN) isolates from the PVY(N) isolates of a geographical region. With this information of regional relationships of PVY(NTN) and PVY(N) isolates, two approaches were developed based on a competitive RT-PCR and a restriction pattern, for the differentiation of NA-PVY(NTN) from the local PVY(N) and from EU-PVY(NTN). Thus sequencing of the P1 gene and use of competitive RT-PCR approach could be applicable for determining the possible origin of new occurrences of PVY(NTN) from other geographical regions.

Analysis of the P1 gene sequences and the 3'-terminal sequences and secondary structures of the single-stranded RNA genome of Potato virus V

The immunocapture reverse transcriptase PCR method (IC-RT-PCR) was used to selectively amplify specific genome sequences of an isolate of Potato virus V (PVV, genus Potyvirus) from a potato plant infected by multiple viruses in the field in Finland. The sequences of the 5'- and 3'-non-translated regions (NTR) and the P1-and coat protein (CP)-encoding sequences were determined because they are the most variable genomic regions in potyviruses. The sequences of the new Finnish PVV isolate obtained in this study were compared to the sequences of eight PVV isolates characterized from other European countries. The results indicated little genetic variability among the European PVV isolates (nt identity values > 96% for all regions examined). Most PVV isolates were grouped according to their geographical origin using P1-sequences for a phylogenetic analysis. The nucleotide substitution patterns for P1 and the CP genes revealed that variability is due to a random genetic drift. Comparison of the secondary structure predictions for the unusually long 3'-non-translated region (3'-NTR) of PVV to the 3'-NTR of Tobacco etch virus (TEV) and other potyviruses revealed that some of the structures defining regions crucial for viral genome replication in TEV are present in PVV and other potyviruses.

Potato Tuber Necrotic Ringspot Disease Occurring in Japan: Its Association with Potato virus Y Necrotic Strain

Unfamiliar necrotic symptoms on or within potato tubers of cultivars Nishiyutaka and Dejima were observed in Nagasaki prefecture, Japan, in 1992. Symptoms were typically on the surface of the tuber, which either protruded at first and then became sunken, or showed necrotic spots, with necrosis within the tubers. Symptoms sometimes appeared at harvesting but more often appeared after storage for several months. Investigations revealed that the causal agents of the disease were isolates of Potato virus Y necrotic strain (PVY^NTN) and the disease was potato tuber necrotic ringspot disease (PTNRD), previously reported in Europe and Lebanon. Five potato cultivars were inoculated with an isolate from necrotic tubers. The highest percentage of progeny tubers showing PTNRD was found in cv. Nishiyutaka (23.3%). In contrast, cvs. Shima-bara, Mayqueen, and Danshaku showed a low percentage of PTNRD. Additional potato tubers with PTNRD were also observed after storage of the tubers. To investigate the relatedness between isolates of PVY^NTN and of necrotic strain PVY^N, previously isolated in Japan, Nishiyu-taka was inoculated with an isolate of PVY^N, which also induced PTNRD. Nucleotide sequences of coat protein (CP) genes of six PVY^NTN isolates were determined. The CPs were 267 amino acids in length, with a substitution of one or no amino acid among each of the six isolates. The phylogenetic relationship based on nucleotide sequences of CP genes showed that these six PVY^NTN isolates clustered together with PVY^N isolates. This is the first report of PTNRD caused by PVY^NTN isolates in Asia.