Pepino mosaic virus isolates and differential symptomatology in tomato

Based on a survey conducted in commercial tomato production in Belgium in 2006, four Pepino mosaic virus (PepMV) isolates that differed in symptom expression in the crop of origin were selected for greenhouse trials. The selected isolates were inoculated onto tomato plants grown in four separate plastic tunnels. PepMV symptom development was assessed regularly and extensive sampling followed by ELISA analyses, genotyping and sequencing was performed to study viral presence and variation in PepMV sequences throughout the trial period. Two isolates (EU-mild and CH2-mild) that were selected based on mild symptom expression in the crop of origin caused only mild symptoms in the trial, while two other isolates (CH2-aggressive and EU + CH2) that were selected for severe symptom display, caused considerably more severe symptoms. Sequence homology between CH2-mild and CH2-aggressive was as high as 99·4%. Results of this study show that differential symptom expression can, at least partially, be attributed to the PepMV isolate, which may be related to minor differences at the nucleotide level between isolates.     

Phylodynamics of Pepino mosaic virus in Spain

Pepino mosaic virus (PepMV) is an emerging pathogen that causes severe economic losses in tomato crops in the Northern hemisphere. After its first identification, the new viral strain PepMV-CH2 has been isolated in several countries worldwide. In order to further understand the evolutionary dynamics of PepMV before and after PepMV-CH2 emergence, we analyzed a collection of PepMV isolates from southeastern Spain, estimating the rate of PepMV molecular evolution and the coalescence process for the effective number of PepMV infections using a Bayesian phylogenetic approach. Our results show that the rate of PepMV molecular evolution was 5.570?×?10^?3 substitutions/site/year, a value which is approximately an order of magnitude higher than the rates recently reported for other plant RNA viruses. Moreover, PepMV-CH2 was estimated to have originated in 2000, coincident with the onset of PepMV-CH2 infections in southeastern Spain, its population following now an expansion process. This further illustrates that genetic and ecological interactions among different viral strains can modulate the evolutionary dynamics of PepMV and determine its epidemiological profile.     

Transmission of the Pepino mosaic virus by whitefly

Two experiments were conducted to investigate the transmission of the Pepino mosaic virus (PepMV) by the greenhouse whitefly (Trialeurodes vaporariorum) from tomato to tomato. In the 1:1 system (in which a single virus-contaminated plant was placed next to a healthy plant in a cage containing 469 whiteflies on average) the virus was transmitted to three out of 10 plants. In the 1:4 system (in which a virus-contaminated plant was surrounded by four healthy plants in a cage with 601 whiteflies on average) the virus was transmitted to five out of 32 plants. In order to investigate the mechanism involved in the transmission, the insect bodies were washed to determine the external presence of viral particles. The results showed that the number of PepMV particles carried on whitefly bodies was low, with an average occurrence of 1.33 on the 55 whiteflies tested after the insects were in contact with infected plants for 5 days. This low occurrence was confirmed by observation under microscope, which showed an absence of PepMV-contaminated tomato sap on the insect bodies, suggesting that PepMV transmission by whiteflies could occur when they feed on the plant.     

Host range and some properties of Physalis mosaic virus,a new virus of the turnip yellow mosaic virus group

An apparently undescribed virus was isolated fromPhysalis subglabrata in Illinois, USA, and its properties were studied. The virus was namedPhysalis mosaic virus (PMV). It was readily transmitted by sap inoculation to 23 out of 34 Solanaceae tested, toChenopodium foetidum andSonchus oleraceus but not to 28 other non-solanaceous species inoculated. Purified preparations of PMV contained isometric particles of 27 nm in diameter, which sedimented as two components with sedimentation coefficients of 50 and 112 S. The 112 S component was infectious, the 52 S component was not. The virus contained 38% ribonucleic acid with a molar base content of G 14.4%, A 22.9%, C 37,2% and U 25.5%.Purified preparations were highly infectious; a concentration of about 6000 particles per ml was infectious on plants.PMV is a member of the Andean potato latent virus subgroup of the turnip yellow mosaic virus group. The virus was closely related to the viruses: Andean potato latent, belladonna mottle, dulcamara mottle and egg-plant mosaic.Samenvatting Een nog niet eerder beschreven virus, dat in de staat Illinois (V.S. van Amerika) opPhysalis subglabrata was gevonden, werd in Wageningen bestudeerd. Het virus dat Physalis mosaic virus (PMV) (in het Nederlands:Physalis-mozaïekvirus) werd genoemd, kon met sap worden overgebracht.BehalveChenopodium foetidum enSonchus oleraceus bleken ook 23 van de 34 getoetste soorten uit de familie Solanaceae vatbaar voor dit virus te zijn. Gezuiverde virus preparaten bevatten isometrische deeltjes met een diameter van 27 nm (Fig. 2) Het virus bestaat uit twee deeltjes met sedimentatie-coëfficiënten van 112 en 50 S. Het 112 S deeltje bleek infectieus te zijn, het andere niet. Op grond van de sedimentatiecoëfficiënten kan worden berekend dat het 112 S deeltje 38% nucleïnezuur bevat. Voor de basenverhouding in het nucleïnezuur werd 22,9% adenine, 14,4% guanine, 37,2% cytosine en 25,5% uracil gevonden (Tabel 1). Het hoge gehalte van cytosine kwam ook tot uiting in de U.V. absorptiekromme van het virus en het nucleïnezuur (Fig. 1). Het gezuiverde virus bleek zeer infectieus te zijn; 6000 deeltjes/ml waren in staat een plant van de soortNicotiana clevelandii ziek te maken.Op grond van serologisch onderzoek kon het virus tot de turnip yellow mosaic virus groep worden gerekend. Het vertoonde serologische verwantschap met de Andean potato latent virus (APLV) subgroep (Tabel 2). In premunitieproeven bood het slechts een geringe bescherming tegen APLV en dulcamara mottle virus. Het omgekeerde werd eveneens geconstateerd. De leden van de APLV-subgroep kunnen op grond van hun waardplantenreeks van elkaar onderscheiden worden (Tabel 3).     

Characterization of two distinct Polish isolates of Pepino mosaic virus

In Poland in 2002 and 2005 two different isolates of Pepino mosaic virus signed PepMV-SW and PepMV-PK were obtained. Both isolates were compared on the basis of their symptomatology on a series of plant species. In addition, the isolates were characterized by the nucleotide sequence analysis of the triple gene block, coat protein and a part of the polymerase genes. The studies showed that the Polish isolates differ from each other and belong to two strains. PepMV-SW was highly similar to European isolates, showing extensive sequence identity, ca. 99%. Pairwise comparisons of PepMV-PK with other PepMV isolates from the GenBank database showed that the highest nucleotide sequence identity was with two isolates: Ch2 from Chile and US2 from the USA.     

PM 7/113 (1) Pepino mosaic virus

Specific scope

This standard describes a diagnostic protocol for detection and identification of Pepino mosaic virus in all plant parts, particularly on tomato seeds ¹ .

Specific approval and amendment

Approved in 2012‐09.     

Host Range and Characterization of Sunflower mosaic virus

ABSTRACT Sunflower mosaic is caused by a putative member of the family Potyviridae. Sunflower mosaic virus (SuMV) was characterized in terms of host range, physical and biological characteristics, and partial nucleotide and amino acid sequence. Cells infected with SuMV had cytoplasmic inclusion bodies typical of potyviruses. Of 74 genera tested, only species in Helianthus, Sanvitalia, and Zinnia, all Asteraceae, were systemic hosts. Commercial sunflower hybrids from the United States, Europe, and South Africa were all equally susceptible. The mean length of purified particles is approximately 723 nm. The virus was transmitted by Myzus persicae and Capitphorus elaegni, and also was seedborne in at least one sunflower cultivar. Indirect enzyme-linked immunosorbent assay tests with a broad-spectrum potyvirus monoclonal antibody were strongly positive. SuMV-specific polyclonal antisera recognized SuMV and, to a lesser extent, Tobacco etch virus (TEV). When tested against a panel of 31 potyvirus-differentiating monoclonal antibodies, SuMV was distinct from any potyvirus previously tested. SuMV shared four epitopes with TEV, but had a reaction profile more similar to Tulip breaking virus (TBV). SuMV did not possess epitopes unique only to TBV. The predicted coat protein had a molecular weight of 30.5 kDa. The 3' end of the virus genome was cloned and sequenced. Phylogenetic analysis of the coat protein amino acid sequence revealed that SuMV is a distinct species within the family Potyviridae, most closely related to TEV.     

Genetic Structure of the Population of Pepino mosaic virus Infecting Tomato Crops in Spain

ABSTRACT The population structure of Pepino mosaic virus (PepMV), which has caused severe epidemics in tomato in Spain since 2000, was analyzed. Isolates were characterized by the nucleotide sequence of the triple gene block and coat protein gene and, for a subset of isolates, a part of the RNA-dependent RNA polymerase gene. The full-length sequence of the genomic RNA of a Solanum muricatum isolate from Peru also was determined. In spite of high symptom diversity, the Spanish population of PepMV mostly comprised highly similar isolates belonging to the strain reported in Europe (European tomato strain), which has been the most prevalent genotype in Spain. The Spanish PepMV population was not structured spatially or temporally. Also, isolates highly similar to those from nontomato hosts from Peru (Peruvian strain) or to isolate US2 from the United States (US2 strain) were detected at lower frequency relative to the European strain. These two strains were detected in peninsular Spain only in 2004, but the Peruvian strain has been detected in the Canary Islands since 2000. These results suggest that PepMV was introduced into Spain more than once. Isolates from the Peruvian and US2 strains always were found in mixed infections with the European tomato strain, and interstrain recombinants were detected. The presence of different strains of the virus, and of recombinant isolates, should be considered for the development of control strategies based on genetic resistance.     

A transgenic RNAi approach for developing tomato plants immune to Pepino mosaic virus

RNA interference (RNAi) or gene silencing is a natural defence response of plants to invading viruses. Here, we applied this approach against pepino mosaic virus (PepMV) isolates in their natural host, tomato. PepMV isolates differ in their genetic sequences, the severity of the disease they induce, and their worldwide distribution. PepMV causes heavy crop losses, mainly due to impaired tomato fruit quality. Resistant varieties are not yet available, despite many years of resistance breeding efforts within the tomato seed industry. To generate broad resistance to PepMV strains, conserved sequences from three different strains of PepMV (US1, LP, and CH2) were synthesized as a single insert and cloned in a hairpin configuration into a binary vector, which was used to transform tomato plants. Transgenic tomato lines that expressed a high level of transgene-siRNA exhibited immunity to PepMV strains, including a new Israeli isolate. This immunity was maintained even after graft inoculation, in which a transgenic scion was grafted onto nontransgenic infected rootstocks. However, an immune transgenic rootstock was unable to induce resistance in a nontransformed scion. These results provide the first example of engineered immunity to diverse PepMV strains in transgenic tomato based on gene silencing.     

Identification and characterization of Pepino mosaic potexvirus in tomato

At the beginning of 1999, a new virus disease occurred in protected tomato crops in The Netherlands. Initial diagnostic tests revealed the presence of a potexvirus but serological tests ruled out the presence of Potato X potexvirus (PVX). Tests for other potexviruses reported from solanaceous crops provisionally identified the virus as Pepino mosaic potexvirus (PepMV). The virus was purified, and an antiserum was produced, which showed strong reactions with both the type isolate of PepMV from pepino and two other isolates from tomato. Host range and symptomatology of the pepino and tomato isolates of PepMV revealed clear differences from PVX. However, differences were also observed between the pepino and tomato isolates of PepMV. Sequence alignment of DNA fragments of 584 bp derived from the RNA polymerase cistron showed almost 95% identity with the pepino isolate, whereas the identity with PVX appeared to be < 60%. Together, these results identified PepMV as the causal agent of the new virus disease in tomato. Based on the differences from the type isolate from pepino ( Solanum muricatum ), the isolates from tomato should be considered as a distinct strain of PepMV for which the name tomato strain is proposed.     

Effect of Pepino mosaic virus on the yield and quality of glasshouse-grown tomatoes in the UK

Two fully replicated trials were conducted with glasshouse-grown tomatoes, under conditions similar to commercial production, to define the impact of Pepino mosaic virus (PepMV). PepMV was not found to reduce bulk yields in these trials, but the quality of tomato fruits harvested was reduced significantly. Compared with uninoculated, PepMV-free control plants, 6·5% of fruits of PepMV-affected cv. Espero were downgraded from class 1 in trial 1. In trial 2, an average 38% of class 1 fruits from PepMV-affected cvs Espero and Encore were lost as a result of downgrading. Loss of quality was mainly a result of blotchy ripening, gold marbling, gold spot, and symptoms directly attributed to PepMV infection. PepMV infection also affected fruit size. The results are discussed in relation to the demands of multiple retailers in the UK for class 1 tomatoes only.     

Genetic variation and evolutionary analysis of Pepino mosaic virus in Sicily: insights into the dispersion and epidemiology

Pepino mosaic virus (PepMV) is a highly infectious potexvirus that causes a severe disease in tomato (Solanum lycopersicum) crops worldwide. In Sicily, the first outbreak was detected in a single greenhouse in 2005 and it was promptly eradicated. However, in 2008, a large number of greenhouses were simultaneously affected, and it was impossible to eradicate or control the virus. This study addressed the dispersion and the genetic diversity of PepMV isolates obtained from the outbreak in Sicily, in comparison with worldwide PepMV isolates, to gain insight into the factors determining the evolution and epidemiology of the virus. A total of 1800 samples from plants with and without symptoms were collected in the Sicilian provinces of Agrigento, Caltanissetta, Palermo, Ragusa, Siracusa and Trapani. Three isolates collected at different times were biologically characterized. The incidence of the virus increased rapidly from 13% in 2011 to 63% in 2013, and phylogenetic analysis showed that all Sicilian isolates of PepMV belonged to the CH2 strain, one of the six strains previously described. Nucleotide diversity of the Sicilian isolates was low, thus suggesting rapid spread and genetic stability.     

Differentiation of strains of bean common mosaic virus

Pathogenicity and symptom expression of seventeen described isolates of bean common mosaic virus (BCMV) and five previously unreported isolates were compared on many bean cultivars (Phaseolus vulgaris L.). From these cultivars, a standard set of differentials were assigned to nine groups with different disease reactions. The twenty-two virus isolates comprised seven strain (pathotype) groups, three of which were divided into two subgroups each. To promote international standardization in BCMV research, recommendations are given for test conditions and procedures, criteria for strain differentiation, and maintenance of differential cultivars and virus strains.Samenvatting Zeventien beschreven stammen van het bonerolmozaïekvirus en vijf niet geïdentificeerde isolaten (Tabel 1) werden bestudeerd op een uitgebreide reeks van toetsrassen. De meeste van deze toetsrassen waren in de literatuur als zodanig vermeld, maar door de desbetreffende onderzoekers waren vaak verschillende series toetsrassen gebruikt, hetgeen de onderlinge vergelijking van de stammen bemoeilijkte.De bedoeling van dit onderzoek was: vergelijking en indeling van de virusstammen, samenstelling van een standaard-toetsrassenserie en het ontwerpen en beschrijven van werden zowel in Wageningen als in Prosser, Washington, USA, uitgevoerd met dezelfde virusisolaten en dezelfde zaadmonsters van de toetsrassen.De toetsrassen konden op grond van hun differentiële reacties na inoculatie met de virusstammen worden ingedeeld in negen groepen. De rassen binnen een groep hebben hetzelfde resistentiespectrum t.o.v. een standaardserie virusstammen. Uit elke groep werden op grond van hun geschiktheid (duidelijkheid en reproduceerbaarheid van de symptomen) één of meer vertegenwoordigers gekozen, waaruit een standaardserie van toetsrassen werd samengesteld (Tabel 2).De 22 stammen en isolaten werden op grond van hun pathogeniteitsspectrum t.o.v. de standaardserie van toetsrassen ingedeeld in tien groepen en subgroepen (Tabel 1). De stammen en isolaten binnen een groep of subgroep hebben eenzelfde pathogeniteitsspectrum (Tabellen 4 en 6) en worden op grond daarvan als identiek beschouwd. De differentiële reacties tussen de rassen van de standaardserie en de virusstammen en-isolaten zijn vermeld in de Tabellen 3 en 5. Voorgesteld wordt om de naam van de eerstbeschreven stam van iedere groep te handhaven en de andere stammen in een groep of subgroep op te vatten als isolaten daarvan.De toetsmethodiek wordt uitvoerig beschreven om standaardisatie van de stammenidentificatie te bevorderen. Ter verklaring van de in de literatuur gevonden tegenstrijdigheden in de differentiële reactie van de toetsrassen wordt een negental mogelijke oorzaken genoemd, o.a. het gebruik van planten van toetsrassen die reeds vanuit zaad met een onbekende stam waren besmet en het gebruik van onzuivere virusstammen (mengisolaten).De auteurs stellen zich verantwoordelijk voor het distribueren (op aanvraag) van kleine zaadhoeveelheden van de toetsrassen en, op beperkte schaal, van in zaad aanwezige zuivere virusstammen aan onderzoekers die betrokken zijn bij de identificatie van de stammen van dit virus. Bovendien zal zaad van de standaardserie van toetsrassen worden gedeponeerd in het National Seed Storage Laboratory te Fort Collins, Colorado, USA, terwijl de virusstammen (in zaad) in bewaring worden gegeven bij de American Type Culture Collection te Rockville, Maryland, USA, waar ze beschikbaar zullen blijven voor verder onderzoek.     

Host differentiation and serological homology of pea seed-borne mosaic virus isolates

Seven isolates of pea seed-borne mosaic virus (PSbMV) were compared on selectedPisum sativum L. differentials and by microprecipitin and SDS-gel serology and particle length. All isolates were characterized by 750 nm particle-length modes and were closely related serologically, but some were readily distinguished onP. sativum differentials. Isolate distinctions were of the magnitude typical for virus strains. Differentials, diversePisum germplasm from U.S. Plant Introduction accessions, provided a practical means of PSbMV strain differentiation.Samenvatting Tussen 1966 en 1970 zijn in verschillende landen virussen gerapporteerd, die bij erwt met zaad overgaan, maar in verschillende opzichten leken te verschillen. Isolaten uit Japan en de USA bleken serologisch nauw aan elkaar verwant, zo niet identiek te zijn. Daarom werd de internationale naam pea seed-borne mosaic virus voorgesteld. In Nederland was het virus beschreven onder de naam erwterolmozaïekvirus.Zeven isolaten van het virus uit de USA, Japan, Tsjechoslowakije en Nederland zijn nader met elkaar vergeleken in reactie op geselecteerde differentiërende rassen van erwt (Pisum sativum) en op enkele andere plantessorten, en in serologische eigenschappen zowel als in deeltjeslengte.Serologisch waren de isolaten niet van elkaar te onderscheiden, wel echter van het verwante bonescherpmozaïekvirus. De voor alle vormen van het laatste virus onvatbare Perfection-type erwterassen bleken al eerder alle vatbaar te zijn voor het erwterolmozaïekvirus. Ook verschillen de isolaten niet in deeltjeslengte (750 nm).Bij toetsing in zes verschillende over de wereld verspreide laboratoria bleek de reactie van de differentiërende erwterassen te variëren van een snelle, de hele plant dodende necrose (groep I) tot onvatbaarheid (groep V). Ook tussen de virusisolaten bestonden kleine verschillen in reactie. Het Nederlandse isolaat E224 gedroeg zich opvallend mild. Ook in de, directe vergelijkingsproeven op enkele toetsplantesoorten bleken kleine biologische verschillen te bestaan. De geconstateerde verschillen overschrijden echter niet die tussen stammen van eenzelfde virus. Wellicht gaat het bij het optreden van necrose en van zwakke symptomen om genen die het vatbaarheidsgensbm modificeren.Contribution of the U.S. Department of Agriculture, Science and Education Administration, Agricultural Research, in cooperation with the Agricultural Experiment Station, Oregon State University, Corvallis. Technical Paper No. 5192, Oregon Agricultural Experiment Station.Mention of a trademark of proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.Authors are members of the International Working Group on Legume Viruses.     

New severe strains of Melon necrotic spot virus: symptomatology and sequencing

New strains of Melon necrotic spot virus (MNSV), designated MNSV-YS and MNSV-KS, caused much more severe growth retardation on melon plants than MNSV-NH, which was previously reported as the most severe strain of MNSV in Japan. MNSV-YS spread much more quickly than MNSV-NH in infected plants, and induced more severe growth retardation, even though the appearance of necrotic lesions on inoculated cotyledons was much slower. MNSV-KS had properties intermediate between those of the other two strains. The results suggest that faster-spreading strains can multiply more rapidly as a result of lower levels of activity in inducing necrotic lesions in melon plants. The complete sequences of MNSV-YS and MNSV-KS were determined, and an RT–PCR–RFLP method based on these sequences was successfully developed to detect and discriminate between the three strains.