Mild Yellow Edge Research Articles

First report of strawberry polerovirus 1 in strawberry in Italy.

Strawberry (Fragaria × ananassa Duch.) was introduced in Sicily (Italy) in the 1930s in the small town of Maletto, on the slopes of Etna volcan, where it's currently cultivated in a total area of 30 ha. The French cv. 'Madame Moutot', appreciated for its unique flavor and intense fragrance, was there propagated vegetatively and after decades, the distinctive 'Etna ecotype' originated by adaptation to the peculiar environmental conditions of the area (Milella et al., 2006). In May 2023, in a 0.5 ha "Etna ecotype" strawberry field, virus-like symptoms were observed in approximately 50% of the plants. Symptoms included severe dwarfing, leaf cupping and chlorotic spotting which lead to decline of infected plants. To investigate the etiology of the disease, leaf samples were collected from eight symptomatic plants for analysis by High-Throughput Sequencing (HTS). To this aim, total RNAs were extracted by using the RNeasy PowerPlant Kit (Qiagen, Germany). The RNAs were pooled, depleted of ribosomal RNA (QIAseq FastSelect; Qiagen), and a library was prepared according to the Illumina DNA Prep Kit. Sequencing on a NextSeq2000 instrument at Leibniz Institute DSMZ (Braunschweig, Germany) generated 31,149,784 of paired-end reads (150 nt), which were further analyzed in Geneious Prime version 2023.2 (Biomatters) using a custom workflow for virus discovery and genome assembly. Analysis of the assembled contigs by local BLASTn and BLASTp alignments against a custom plant virus database of NCBI nuclear-core (NC) reference sequences assigned a number of contigs to accession NC_025435, strawberry polerovirus 1 (SPV-1). Reconstruction of the virus genome by assembly of contigs and reads alignment resulted in a nearly complete genome sequence of SPV-1 (GenBank Acc. No. OR989958) showing by BLASTn 98.69% identity to the SPV-1 NC reference sequence, and 98.99 % identity with an isolate from the Czech Republic (GenBank Acc. OL421571). To confirm the presence of SPV-1 in each sample, RT-PCR using specific primers designed in this study SPV-1-CP-1F (5'-TCGAGATACGTCTAGAACTGCAA-3') and SPV-1-CP-1R (5'-GAGAGGCCCCTTCTACCTATTTG-3') targeting the entire 623 bp coat protein (CP) gene was performed. Amplicons of the expected size were obtained in five samples and Sanger-sequenced. The resulting sequences shared 99.85% - 100% of identity to the HTS - derived sequence (GenBank Acc. No. OR989958) through BLASTn analysis. Strawberry mottle virus (SMoV), strawberry mild yellow edge virus (SMYEV) and strawberry crinkle virus (SCV) were detected in the same library in addition to SPV-1 and then confirmed by RT-PCR using specific primers (Martin & Tzanetakis 2013). Strawberry polerovirus 1, related to the genus Polerovirus in the family Solemoviridae, was first reported in strawberries in Canada (Xiang et al. 2015) and was thereafter detected in the United States (Thekke-Veetil & Tzanetakis 2016), Argentina (Luciani et al. 2016), and Nepal (Kuwak et al. 2022). To date, the virus has been reported in Europe only in the Czech Republic (Franova et al. 2021). To our knowledge, this is the first report of SPV-1 in strawberry plants in Italy. Although the correlation between SPV-1 and strawberry decline (SD) is still uncertain (Xiang et al. 2015) transmission of the virus via aphids has recently been demonstrated (Franova et al. 2021). Our report let to hypothesize that its dissemination in Europe can be considered as increasing.

Polysaccharide Peptide Treatment Eliminates Strawberry Viruses and Promotes Strawberry Plant Growth and Rooting in Tissue Culture Media.

Based on our previous finding that polysaccharide peptide (PSP) has substantial antiviral activity, we cultured strawberry plants infected with strawberry mild yellow edge virus (SMYEV) or strawberry vein banding virus (SVBV) in Murashige and Skoog (MS) media supplemented with PSP to test its ability to eliminate these viruses. PSP not only improved the elimination of SMYEV and SVBV but also promoted the growth and rooting of strawberry plants in tissue culture. On the 45th day, the average height of the 'Ningyu' strawberry plants in the 1-mg/ml PSP treatment group was 1.91 cm, whereas that of the plants in the control group was 1.51 cm. After the same time point, the number of new leaves on the tissue culture media supplemented with 1 mg/ml and 500 μg/ml of PSP and without PSP were 4.92, 4.41, and 3.53, respectively. PSP also promoted strawberry rooting and significantly increased both the length and number of roots. In addition, after treatment with the 1-mg/ml PSP treatment in tissue culture for 45 days followed by meristem-shoot-tip culture, the elimination rates of SMYEV and SVBV in regenerated 'Ningyu' strawberry plants ranged from 60 to 100%. This study investigated the use of the antiviral agent PSP for virus elimination. PSP has a low production cost and thus has great application potential for virus elimination in crop plants.

Rapid Detection of Strawberry Mild Yellow Edge Virus with a Lateral Flow Strip Reverse Transcription Recombinase Polymerase Amplification Assay.

Strawberry mild yellow edge virus (SMYEV) is a latent virus that severely affects the yield and quality of strawberry fruit. The technology suitable for rapid and accurate detection of SMYEV on site is important to effectively control its spread. In this study, a reverse transcription recombinase polymerase amplification combined with lateral flow strip (SMYEV-RT-RPA-LF), targeting the conserved genome of Beijing SMYEV isolate, was established to diagnose SMYEV in strawberries. The SMYEV-RT-RPA-LF assay showed no cross-reaction with other strawberry viruses. The sensitivity of SMYEV-RT-RPA-L assay was 100 times higher than that of RT-PCR (10pg/μL). In addition, through the detection of suspected samples in the field, it was found that the accuracy of SMYEV-RT-RPA-L assay was consistent with the RT-PCR results. However, compared with RT-PCR, SMYEV-RT-RPA-LF assay has the advantages of simple operation, time savings, and high specificity and sensitivity, indicating the potential application of SMYEV-RT-RPA-LF in the rapid field diagnosis of SMYEV.

Identification and Characterization of a Novel Umbra-like Virus, Strawberry Virus A, Infecting Strawberry Plants.

A novel RNA virus infecting strawberry plants was discovered using high-throughput sequencing. The analyzed plant was simultaneously infected with three different genetic variants of the virus, provisionally named strawberry virus A (StrVA). Although StrVA is phylogenetically clustered with several recently discovered, unclassified plant viruses, it has a smaller genome and several unique features in its genomic organization. A specific and sensitive qPCR system for the detection of identified StrVA genetic variants was designed. A survey conducted in the Czech Republic revealed that StrVA was present in 28.3% of strawberry samples (n = 651) from various origins (plantations, gardens, and propagation material). Sequencing of 48 randomly selected StrVA-positive strawberry samples showed that two or all three StrVA genetic variants were present in 62.5% of the samples in various proportions. StrVA was found in mixed infections with other viruses (strawberry mild yellow edge virus, strawberry crinkle virus, strawberry mottle virus, strawberry polerovirus 1, or strawberry virus 1) in 57.1% of the samples, which complicated the estimation of its biological relevance and impact on the health status of the plants.

High Incidence of Strawberry Polerovirus 1 in the Czech Republic and Its Vectors, Genetic Variability and Recombination.

In total, 332 strawberry plants from 33 different locations in the Czech Republic with or without disease symptoms were screened by RT-PCR for the presence of strawberry polerovirus 1 (SPV1) and five other viruses: strawberry mottle virus, strawberry crinkle virus, strawberry mild yellow edge virus, strawberry vein banding virus, and strawberry virus 1. SPV1 was detected in 115 tested strawberry plants (35%), including 89 mixed infections. No correlation between symptoms and the detected viruses was found. To identify potential invertebrate SPV1 vectors, strawberry-associated invertebrate species were screened by RT-PCR, and the virus was found in the aphids Aphis forbesi, A. gossypii, A. ruborum, A. sanquisorbae, Aulacorthum solani, Chaetosiphon fragaefolii, Myzus ascalonicus, and several other non-aphid invertebrate species. SPV1 was also detected in aphid honeydew. Subsequent tests of C. fragaefolii and A. gossypii virus transmission ability showed that at least 4 h of acquisition time were needed to acquire the virus. However, 1 day was sufficient for inoculation using C. fragaefolii. In conclusion, being aphid-transmitted like other tested viruses SPV1 was nevertheless the most frequently detected agent. Czech SPV1 isolates belonged to at least two phylogenetic clusters. The sequence analysis also indicated that recombination events influence evolution of SPV1 genomes.

Preliminary Study of Viruses Infecting Strawberry (Fragaria spp.) in the Midsouthern United States

Strawberry is an important economic crop in the midsouthern United States; however, limited information is known about the viruses present in strawberry fields in Arkansas, Missouri, Oklahoma, and Texas. The purpose of this study was to determine the presence of particular viruses infecting strawberry crops in these four states. A total of 816 strawberry leaf samples were randomly collected from growers’ fields during the 2014 and 2016 growing seasons and tested by dot-immunobinding assay against antisera of eight available viruses: apple mosaic virus (ApMV), arabis mosaic virus (ArMV), raspberry bushy dwarf virus (RBDV), raspberry ringspot virus, strawberry mild yellow edge virus (SMYEV), tobacco necrosis virus, tomato black ring virus, and tomato ringspot virus (ToRSV). Of the eight viruses, ApMV, RBDV, and SMYEV had the highest infection rates in 2014, whereas ApMV, ArMV, ToRSV and SMYEV were the most prevalent viruses in 2016. Mixed infection of more than one virus was very common in samples collected from all four states. Our preliminary results showed that the distribution of virus relative frequencies differed significantly among seven sample locations across the states within a sample year, but we could not show statistical differences among the years based on our sample sizes. Mixed infections in strawberries were higher than expected in 2014 and lower than expected in 2016 based on viruses being independent infections. Overall, the occurrence of the viruses in strawberry crops could have important potential impacts for strawberry production in the midsouthern states.

Viral Diseases of Strawberry

Viral diseases in strawberry are not easily detected because most single virus infections are symptomless on commercial cultivars. However, virus outbreaks have the potential for epidemics and economic losses. A mixed virus infection of Strawberry Mild Yellow Edge Virus (SMYEV) and Strawberry Mottle Virus (SMoV) was identified in several southeastern states during the 2012-13 season, resulting in millions of dollars in losses. 
 This updated version of a previous publication offers basic information on viral diseases of strawberry, with emphasis on viruses of potential threat to the strawberry industry in Florida. The primary target audience of this publication includes growers and industry personnel, extension agents and pathologists working with strawberry.
 Originally published April 2010: Moyer, Catalina, Vance Whitaker, and Natalia Peres. 2010. “Viral Diseases of Strawberries”. EDIS 2010 (4). https://journals.flvc.org/edis/article/view/118602.

Sequencing a Strawberry Germplasm Collection Reveals New Viral Genetic Diversity and the Basis for New RT-qPCR Assays.

Viruses are considered of major importance in strawberry (Fragaria × ananassa Duchesne) production given their negative impact on plant vigor and growth. Strawberry accessions from the National Clonal Germplasm Repository were screened for viruses using high throughput sequencing (HTS). Analyses of sequence information from 45 plants identified multiple variants of 14 known viruses, comprising strawberry mottle virus (SMoV), beet pseudo yellows virus (BPYV), strawberry pallidosis-associated virus (SPaV), tomato ringspot virus (ToRSV), strawberry mild yellow edge virus (SMYEV), strawberry vein banding virus (SVBV), strawberry crinkle virus (SCV), strawberry polerovirus 1 (SPV-1), apple mosaic virus (ApMV), strawberry chlorotic fleck virus (SCFaV), strawberry crinivirus 4 (SCrV-4), strawberry crinivirus 3 (SCrV-3), Fragaria chiloensis latent virus (FClLV) and Fragaria chiloensis cryptic virus (FCCV). Genetic diversity of sequenced virus isolates was investigated via sequence homology analysis, and partial-genome sequences were deposited into GenBank. To confirm the HTS results and expand the detection of strawberry viruses, new reverse transcription quantitative PCR (RT-qPCR) assays were designed for the above-listed viruses. Further in silico and in vitro validation of the new diagnostic assays indicated high efficiency and reliability. Thus, the occurrence of different viruses, including divergent variants, among the strawberries was verified. This is the first viral metagenomic survey in strawberry, additionally, this study describes the design and validation of multiple RT-qPCR assays for strawberry viruses, which represent important detection tools for clean plant programs.

First report of the complete genomic sequences of strawberry mild yellow edge virus and strawberry vein banding virus isolated in Japan

Strawberry vein banding virus (SVBV) and strawberry mild yellow edge virus (SMYEV) have caused disease in strawberries for many years in Japan, but little is known about their molecular properties. We thus determined the complete genomic sequence of an isolate of each virus from Tochigi Prefecture. A nucleotide sequence analysis showed that SVBV is closely related to Chinese isolates, whereas SMYEV is closely related to German and Argentine isolates. This is the first report describing the complete genome sequences of SVBV and SMYEV isolated in Japan. Moreover, we constructed an infectious SMYEV clone, which induced mild yellowing on inoculated strawberry plants.

Genetic diversity of strawberry mild yellow edge virus from eastern Canada.

Strawberry mild yellow edge virus (SMYEV) is a member of the genus Potexvirus, family Alphaflexiviridae. It is one of the most common pathogenic viruses infecting cultivated strawberries worldwide. In this study, we investigated the genetic diversity of SMYEV in strawberry fields that were severely affected by strawberry decline disease in the eastern Canadian provinces of New Brunswick, Nova Scotia, Prince Edward Island and Quebec. A total of 134 SMYEV coat protein (CP) gene sequences, representing 85 nucleic acid haplotypes, were identified in 56 field samples. A highly divergent SMYEV population was found in all four provinces, but there was little genetic differentiation among the populations, and moreover, the Canadian SMYEV isolates formed a unique dissimilar, genetically divergent population group when compared to those reported in other countries. Phylogenetic analysis revealed three new SMYEV subclades that consisted mainly of Canadian variants and were composed of 76 sequence haplotypes (76/85, 88%). Mixed infections by different SMYEV variants were observed in 38 samples (38/56, 68%). Evolutionary analysis suggested that the SMYEV strains in eastern Canada possibly originated outside of Canada but adapted to conditions in the region through genetic mutations.

Incidence of Aphid-Transmitted Strawberry Viruses in Korea and Phylogenetic Analysis of Korean Isolates of Strawberry Mottle Virus

Among more than 30 viruses infecting strawberry, aphid-transmitted viruses including Strawberry mild yellow edge virus (SMYEV), Strawberry mottle virus (SMoV), Strawberry crinkle virus (SCV), and Strawberry vein banding virus (SVBV) have been considered as the most economically important viruses of strawberry in the world. To determine the incidence of these four viruses in major Korean strawberry cultivars, field surveys were conducted in major production areas during 2018-2019. In our surveys, SMYEV and SMoV were detected with low infection rates of 0.7% and 1.3%, respectively, whereas SCV and SVBV were not detected. No obvious symptoms were observed in the strawberry plants infected by SMYEV or SMoV. Since no sequences of SMoV Korean isolates have been reported, we initially determined nucleotide sequence of the 3' untranslated region (UTR) of seven SMoV isolates obtained during the surveys. The 3' UTR sequences (782 nt) of seven Korean isolates were phylogenetically compared with those of the previously reported SMoV isolates. Phylogenetic analysis revealed that most Korean isolates are closely related to Canadian isolates and only little evolutionary differentiation occurred among the Koreans isolates. This might be due to the low incidence of SMoV in strawberry in Korea.

Pest categorisation of non-EU viruses of Fragaria L.

Following a request from the EU Commission, the Panel on Plant Health addressed the pest categorisation of the viruses and viroids of Fragaria L. determined as being either non‐EU or of undetermined standing in a previous EFSA opinion. These infectious agents belong to different genera and are heterogeneous in their biology. With the exclusion of strawberry latent virus and strawberry latent C virus for which very limited information exists, the pest categorisation was completed for 12 viruses having acknowledged identities and available detection methods. All these viruses are efficiently transmitted by vegetative propagation techniques, with plants for planting representing the major pathway for long‐distance dispersal and thus considered as the major pathway for entry. Depending on the virus, additional pathway(s) can also be Fragaria seeds, pollen and/or vector(s). Most of the viruses categorised here are known to infect only one or few plant genera, but some of them have a wide host range, thus extending the possible entry pathways. Strawberry chlorotic fleck‐associated virus, strawberry leaf curl virus, strawberry necrotic shock virus, strawberry pallidosis‐associated virus, strawberry vein banding virus (SVBV) and tomato ringspot virus meet all the criteria evaluated by EFSA to qualify as potential Union quarantine pests (QPs). For SVBV, the Panel considered that following its entry and establishment into the EU territory, an impact of uncertain magnitude is expected mainly because a synergistic effect may occur in strawberry in case of mixed infections with viruses already present in the EU . Strawberry crinivirus 3, strawberry crinivirus 4 and strawberry polerovirus 1 meet all criteria for being considered as potential Union QPs, except for the impact in the EU territory, on which the Panel was unable to conclude. Fragaria chiloensis cryptic virus, Fragaria chiloensis latent virus and strawberry pseudo mild yellow edge virus do not meet the criterion of having potential negative impact in the EU. For several viruses, especially those recently discovered, the categorisation is associated with high uncertainties mainly because of the absence of data on their biology, distribution and impact. Since this opinion addresses specifically the non‐EU viruses, in general, these viruses do not meet the criteria assessed by EFSA to qualify as potential Union regulated non‐quarantine pests.

Evaluation of Various Sources of Viral Infection in Strawberry Fields of Quebec, Canada

The decline of cultivated strawberry (Fragaria × ananassa Duchesne ex Rozier; Rosaceae) observed in the province of Quebec, Canada, between 2012 and 2014 was mostly caused by persistent viruses: strawberry mild yellow edge virus (SMYEV) (Potexvirus; Alphaflexiviridae) and strawberry crinkle virus (SCV) (Cytorhabdovirus; Rhabdoviridae); and semi-persistent viruses: strawberry mottle virus (SmoV) (Secoviridae), strawberry vein banding virus (SVBV) (Caulimovirus; Caulimoviridae), and strawberry pallidosis virus (SPaV) (Crinivirus: Closteroviridae) transmitted by insect vectors. The objective of this study was to determine the sources of viral contamination in commercial strawberry fields in Quebec. Specifically, we wished to 1) determine the prevalence of persistent viruses in winged strawberry aphid Chaetosiphon fragaefolii (Cockerell) (Hemiptera: Aphididae) specimens captured; 2) determine the prevalence of all viruses in wild strawberry Fragaria virginiana Miller plants near commercial plantings; and 3) evaluate the viral contamination of strawberry transplants obtained from nurseries and tested before and after planting in commercial strawberry fields. Results indicated high percentage (38%) of the aphids (n = 205) and high percentage (67%) of F. virginiana patches (n = 12) were infected by strawberry viruses. Ultimately, our results showed a low percentage (5%) of the plants from various nurseries (n = 56) were infected before planting, whereas a third (29%) of the healthy exposed plants in the fields (n = 96) became rapidly infected by insect vectors within a year of having been planted. This study provides significant insights on the relative importance of the various sources of contamination in Quebec strawberry fields: C. fragaefolii versus F. virginiana versus nurseries versus post-nursery infections through exposure to virus-carrying insects.

Complete nucleotide sequence of a new potexvirus, 'Cnidium virus X', isolated from Cnidium officinale in Japan.

A flexuous virus was detected in a Cnidium officinale plant in Japan showing mosaic symptoms. The virus was assigned to the genus Potexvirus based on analysis of its complete nucleotide sequence. The genomic RNA of the virus was 5,964 nucleotides in length, excluding the 3'-terminal poly(A) tail. It contained five open reading frames (ORFs), consistent with other members of Potexvirus. The ORF sequences differ from those of previously reported potexviruses. Phylogenetic analysis indicated that the polymerase of the virus is closely related to that of strawberry mild yellow edge virus; and the CP, to those of both yam virus X and vanilla virus X. We propose that this virus be designated as "cnidium virus X" (CnVX).

Genetic Diversity of Two Isolates in Strawberry mild yellow edge virus from Korea

Genetic Diversity of Two Isolates in Strawberry mild yellow edge virus from Korea

Incidence and prevalence of aphid‐borne viruses infecting strawberry in Argentina

The incidence and prevalence of strawberry viruses were determined in surveys of randomly selected strawberry plants grown in different regions of Argentina. In 2009 and 2010, 1034 plants from 28 fields and 1060 plants from 33 fields, respectively, were collected from Lules and Coronda. The samples were analysed by double‐antibody sandwich enzyme‐linked immunosorbent assay to detect Strawberry mild yellow edge virus (SMYEV). In 2014, 606 plants from 43 fields in Lules, Coronda and Mar del Plata were analysed by reverse transcription polymerase chain reaction with primers specific for SMYEV, Strawberry crinkle virus (SCV), Strawberry mottle virus (SMoV) and Strawberry polerovirus 1 (SPV1). The SMYEV incidence was 4–35%, while prevalence was 60–100%, depending on the year and region sampled. Meanwhile, SMoV and SPV1 incidences were 8–17%, and prevalences were 46–62%, depending on the virus and region sampled. SCV was observed relatively low (incidence was 0.5–8% and prevalence was 8–50%), although it was more abundant in Mar del Plata than in the other analysed regions. Spearman's correlation analysis indicated that SCV and SMYEV were correlated with disease symptoms (P < 0.005). A principal component analysis revealed a close relationship between SMYEV and SCV in Mar del Plata, in which the lowest temperatures were recorded. Interactions among viruses, regions and climatic conditions will need to be studied in greater detail. Accurately determining the incidence and prevalence of viruses in different regions will improve estimations of possible damages or yield decreases caused by viral infections during strawberry production.

Characterization of the complete genome of euonymus yellow vein associated virus, a distinct member of the genus Potexvirus, family Alphaflexiviridae, isolated from Euonymus bungeanus Maxim in Liaoning, Northern China.

In August 2016, a yellow vein disease was observed on leaves of Euonymus bungeanus Maxim (Euonymus, Celastraceae) in Liaoning, China. Virions measuring 750 × 13 nm were observed in a sample from the diseased plant. A potexvirus was detected in the sample by small-RNA deep sequencing analysis and recovered by traditional cloning. The genome of this potexvirus consists of 7,279 nucleotides, excluding the poly(A) tail at the 3' end, and contains five open reading frames (ORFs). Based on the nucleotide and amino acid sequences of the coat protein gene, the virus shared the highest sequence similarity with white clover mosaic virus (WCMV, X16636) (40.1%) and clover yellow mosaic virus (ClYMV, D00485) (37.1%). Phylogenetic analysis showed that the virus clustered with potexviruses and is most closely related to strawberry mild yellow edge virus. These results indicate that this virus is a distinct member of the genus Potexvirus, for which the name euonymus yellow vein associated virus (EuYVAV) is proposed. To our knowledge, this is the first report of a potexvirus on E. bungeanus.

Yield losses of asymptomatic strawberry plants infected with Strawberry mild yellow edge virus

After successive vegetative propagation cycles, strawberry (Fragaria × ananassa Duch.) plants often accumulate multiple virus species that result in viral symptoms and losses in yield and quality. However, strawberry plants infected by a single virus species usually remain asymptomatic with unknown effects on fruit production and quality. In this context, the effect of Strawberry mild yellow edge virus (SMYEV) on fruit production was studied in strawberry plants, cultivar Camarosa, over two years. Asymptomatic SMYEV-infected plants showed a significant reduction in total and marketable fruit number and weight compared with healthy plants. These reductions ranged between 28% and 63%, depending on the parameter measured and the production cycle. Fluctuations in SMYEV concentration in the plants was detected throughout the crop cycle, suggesting that samples for virus diagnosis should be taken when the plant has the highest virus concentration; in this study, this occurred at the end of the crop cycle. These results show that analyzing symptomless strawberry plants should be part of a virus disease management plant and an important component to control the quantitative and qualitative impacts of SMYEV on strawberry yield.

Genetic variability and recombination analysis of the coat protein gene of Strawberry mild yellow edge virus

Strawberry mild yellow edge virus (SMYEV) has been detected in most of the strawberry production regions worldwide. However, little is known about differences between distinct isolates. The aim of this study was to enhance the knowledge about the genetic variability of different SMYEV isolates, exploring the phylogenetic relationships and assessing recombinant events among them. The coat protein (CP) gene of 12 Argentinian SMYEV isolates was sequenced. There were 729 nucleotides (nt) in all of the isolates, encoding a protein of 242 amino acids (aa). Argentina isolates shared 81.5–99.6 % nucleotide identity. The comparison of these isolates with 30 SMYEV sequences from other countries published in the GenBank, revealed an identity ranging from 81.6 to 99 %. The phylogenetic analysis showed the presence of four possible subgroups, with the Argentinian isolates being included in all of them. Recombination analysis indicated that 16–2 (KP 284155) Argentinian and AJ577342 Chilean isolates are recombinant and that they are a result of recombination events where parts of the genome were exchanged between different SMYEV sequences.

Molecular Characterization of Divergent Strawberry Mild Yellow Edge Virus Isolates from Eastern Canada

AbstractThe complete genome sequences of four new isolates of strawberry mild yellow edge virus (SMYEV) were determined and analysed. The isolates, designated as AB41‐01, AB41‐02, NB1165 and NS26, were found from strawberry fields showing strawberry decline symptoms in eastern Canada. AB41‐01 and AB41‐02 were from a single‐plant sample originating from Prince Edward Island, while NB1165 came from New Brunswick and NS26 from Nova Scotia. Nucleotide sequence identities are 95.8% between AB41‐01 and NB1165, 99.6% between AB41‐02 and NS26, and 84% between AB41‐01/NB1165 and AB41‐02/NS26. The four isolates share nucleotide sequence identities of 83.5–89.9% to two previously identified SMYEV isolates, namely MY18 and D7. Phylogenetic analysis indicates that the four Canadian isolates represented two new SMYEV strain types and the strain divergences were not likely from recombination events among all presently known SMYEV isolates.