Shallot Yellow Stripe Virus Research Articles

Molecular Identification of Three Potyviruses Infecting Allium cepa var. aggregatum and Allium sativum in Central Cultivation Areas of Indonesia

One hundred and twenty shallot (Allium cepa var. aggregatum) and 22 garlic (Allium sativum) samples were collected from major growing regions and markets to determine the distribution and molecular diversity of 3 potyviruses: leek yellow stripe virus (LYSV), onion yellow dwarf virus (OYDV), and shallot yellow stripe virus (SYSV) in Indonesia. The results of reverse transcription-polymerase chain reaction (RT-PCR) showed that 83% of shallot and all garlic samples were infected by at least 1 virus species. Coat protein (CP) region of 8 Indonesian LYSV, 19 OYDV, and 10 SYSV isolates were sequenced and given accession nos. OR772038-OR772082 in NCBI GenBank. Five isolates were recombinants according to analysis using the Recombination Detection Program (RDP v5.30). The phylogenetic tree deduced that 6 LYSV Indonesian and 2 China imported isolates belong to S-type. All tested OYDV isolates, including the 19 isolates, were clustered separately according to their respective hosts: onion and garlic. The 10 Indonesian SYSV isolates were clustered together in the same group and thus shown to be closely related. All isolates tested in this study were estimated to be still within their respective species demarcation according to percentage identity analysis. This was the most comprehensive molecular study on LYSV, OYDV, and SYSV that may help to find sustainable management strategies according to conditions in Indonesia and contribute to the global knowledge on the genetic diversity of the 3 viruses.

Application of Multiplex TaqMan Real-Time PCR Assay in Survey of Five Lily Viruses Infecting Lilium spp.

Lily symptomless virus (LSV), Lily mottle virus (LMoV), Cucumber mosaic virus (CMV), Shallot yellow stripe virus (SYSV), and Plantago asiatica mosaic virus (PlAMV) are five of the economically important viruses infecting lilies (Lilium spp.) worldwide. In order to prevent the occurrence and spread of these viruses, it is necessary to develop a rapid, effective, and sensitive detection method for the simultaneous detection and specific quantification of these viruses. In this study, specific primers and probes for multiplex TaqMan real-time PCR assays designed from conserved regions of the coat protein sequence of each virus were used for the simultaneous detection of these viruses in lilies (Lilium spp.). The optimal concentration of primers and probes and reaction annealing temperature were 20 µM and 55.9 °C, respectively. The detection limits of the assay were 1.33 × 102, 1.27 × 101, 1.28 × 101, 2.33 × 102, and 2.01 × 102 copies·μL−1 for LSV, LMoV, CMV, SYSV, and PlAMV, respectively. Specificity was determined using seven viral pathogens of lilies. Variability tests of intra- and inter-assays showed high reproducibility with coefficients of variation <2%. The multiplex TaqMan real-time PCR assay was used to detect these viruses from lily samples in China. In brief, our developed assay showed high specificity, sensitivity, and reproducibility for the simultaneous detection and differentiation of five lily-infecting viruses and can be used for certification and quarantine programs.

Newly identified host range of viruses infecting species of the genus Allium and their distribution in six habitats in the Czech Republic

AbstractStudies on plant viruses are concentrated mainly towards crop diseases and little is known about viruses in wild and ornamental species. We surveyed viruses infecting 65 vegetable, wild, and ornamental Allium species cultivated or naturally occurring in the Czech Republic. Allium plants were collected from six habitat categories (botanical gardens, private gardens, cultivated fields, ornamentals from markets, cultivated plants of wild origin, wild origin). Samples were tested by ELISA and/or reverse transcription‐PCR for the presence of 15 viruses belonging to the genera Allexivirus, Carlavirus, Potyvirus, and Orthotospovirus. Of the 883 sampled plants, 63.4% were infected by at least one or more viruses. The infection rate of Allium samples differed depending on the habitat origin and phylogenetic relatedness of the hosts. Viruses were most frequently detected in cultivated species, with a high incidence of leek yellow stripe virus (LYSV), garlic common latent virus (GCLV), shallot virus X (ShVX), garlic virus A (GarV‐A), and garlic virus B (GarV‐B). Low infection rates and virus‐free samples were detected in species of wild origin. Composition of viruses belonging to the genus Allexivirus significantly differentiated the subgenus Melanocrommyum from other Allium subgenera. Mixed infections (51.1% of analysed plants) were widespread in most species. New host associations were observed for some viruses previously recorded in the Czech Republic. In addition, three viruses, shallot yellow stripe virus (SYSV), Impatiens necrotic spot virus (INSV), and iris yellow spot virus (IYSV), were detected for the first time on Allium species in the Czech Republic.

Detection and Distribution of Viruses Infecting Garlic Crops in Australia.

The distribution of viruses in eastern Australian field garlic was evaluated. Detection assays were developed that involved generic RT-PCR for viruses in the Allexivirus, Carlavirus and Potyvirus genera followed by virus-specific colorimetric dot-blot hybridization. Assays targeted the potyviruses (onion yellow dwarf virus (OYDV), shallot yellow stripe virus (SYSV), and leek yellow stripe virus (LYSV)), the carlaviruses (garlic common latent virus (GCLV) and shallot latent virus (SLV)), and the allexiviruses (garlic viruses A, B, C, X (GarVA, -B, -C, -X) and shallot virus X (ShVX)). Virus incidence in crops was consistently high, with most plants infected with at least one virus from each genus. OYDV, LYSV, SLV, and GCLV were commonly detected. Three of the four allexiviruses were in all districts surveyed but varied in incidence, whereas ShVX and SYSV were not detected. There was no association between virus species complement and bulb size, indicating size is not a good predictor of the virus status of planting material. The variation of virus incidence across different Australian growing districts and in different cultivars implies multiple introductions of viruses rather than spread within the country. The genetic diversity observed within coat protein sequences of some virus species also supports multiple separate introductions.

Sensitivity of serological and polymerase chain reaction methods for detection of viruses in Allium spp.

Infection of Onion yellow dwarf virus (OYDV), Shallot yellow stripe virus (SYSV), and Garlic common latent virus (GCLV) has been reported on Allium spp. in Indonesia. Serology methods using enzyme-linked immunosorbent assay (ELISA), and dot immunobinding assay (DIBA) is a common method to detect viruses, while polymerase chain reaction (PCR) is popular as a molecular method to detect plant viruses nowadays. This research was conducted to assess the sensitivity of 3 detection methods, i.e. ELISA, DIBA and PCR for detecting viruses in Allium spp. Sensitivity level of each method was evaluated by diluting plant extract and antibody for ELISA and DIBA, and cDNA template for PCR. Result of this research showed that DIBA was able to detect OYDV, GCLV, and SYSV with plant extract dilution in the range of 10−1 to 10−2, and antibody dilution from 1:300 to 1:1000. ELISA seems to be more sensitive than DIBA because it was able to detect the same virus with plant extract dilution in the range of 10−1, 10−3, and 10−5, and antibody dilution from 1:300 to 1:1000. RT-PCR method was the most sensitive method compared to ELISA and DIBA because it has the highest accuracy, specification and sensitivity level. Specific DNA fragment was amplified using universal primers for Potyvirus and Carlavirus up to 10−3 and 10−4 dilution factor of cDNA respectively. Moreover, amplification using specific primers of OYDV, SYSV, and GCLV is more sensitive than using universal primers, because up to 10−5 dilution factor of cDNA was able to amplify virus target.

First Report of Shallot yellow stripe virus in Lilium lancifolium in China

Lilium lancifolium (family Liliaceae), also called tiger lily, is widely cultivated in China for its edible bulbs and medicinal application (China Pharmacopoeia Committee 2005; Yu et al. 2015), with a production value of approximately six billion Yuan per year. L. lancifolium is a polyploid complex including both diploid (2n = 2x = 24) and triploid (2n = 3x = 36) cytotypes, and only the triploids are widely distributed in inland China (Kim et al. 2006; Noda 1986). Because the triploids are sterile, therefore L. lancifolium cannot extend its population through seeds but propagates only through an asexual mode. However, vegetative propagation is vulnerable to the accumulation of viruses over subsequent generations. Shallot yellow stripe virus (SYSV), belonging to the genus Potyvirus of the family Potyviridae, was isolated from shallot samples originating from Southeast Asia (Indonesia, China, and Thailand) (Van der Vlugt et al. 1999). A virulent strain of this virus caused striping in sap-inoculated garlic (Allium sativum) and Formosan lily (Lilium formosanum) (Van Dijk 1993). In June 2015, longitudinal yellow stripe symptoms on leaves were observed on approximately 10% of L. lancifolium plants in the greenhouse of the Chinese Academy of Agricultural Sciences (Beijing, China). Total RNA was extracted from 15 symptomatic leaves (lesion covering one-third of leaf area) randomly collected from 10 different plants, and a de novo transcriptome was constructed using the Illumina HiSeq 4000 platform (Novogene Bioinformatics Technology Co., Beijing, China). A total of 54,142,872 paired-end reads of 150 bp were obtained. De novo assembly of the reads generated one large contig (9,843 bp) sharing a maximum nucleotide identity of 85.0% and amino acid identity of 90.6% with SYSV (GenBank accession no. AJ865076) isolated from Welsh onion in China (Chen et al. 2005). To confirm the Illumina sequencing results, the full-length SYSV genome was amplified by reverse transcription PCR (RT-PCR) using seven pairs of specific primers designed from the contig obtained in this study and sequenced. Seven RT-PCR fragments were assembled to obtain an SYSV sequence with a full length of 9,843 bp, which contained a single 9,441-bp complete open reading frame. The sequence shared a nucleotide sequence identity of 98% with the sequence assembled from Illumina RNA-Seq data. The isolate of SYSV from L. lancifolium was named LL01 and was deposited in GenBank under accession MK127536. A pair of specific primers (5′-ATACCCTTTGGTTTCCGC-3′ and 5′-TGCTATCATCACCCTCGC-3′), which amplified a 269-bp fragment, was designed according to the genome sequence of the isolate LL01 to detect SYSV in Lilium species. In total, 30 out of 50 analyzed symptomatic leaf samples (60%) tested positive, whereas negative controls remained negative. SYSV was not detected in 40% of symptomatic samples, suggesting that divergent variants of the virus, or perhaps other viruses, could be associated with the observed symptoms, and further research is needed. To our knowledge, this is the first report on the occurrence and sequence of SYSV in L. lancifolium in China. This report suggests that L. lancifolium plays a possible role as a reservoir host of the virus for Allium species. In addition, growers should plant virus-free bulbs obtained through shoot tip culture combined with heat treatment or medicament treatment.

First records of the potyviruses Chilli ringspot virus and Shallot yellow stripe virus from Laos

Evidence for the presence of Chilli ringspot virus and Shallot yellow stripe virus in Laos is provided for the first time. RT-PCR assays to amplify the coat protein genes of these viruses are described.

The first complete genome sequence of iris severe mosaic virus.

The first complete genome sequence of ISMV was determined by deep sequencing of a small RNA library constructed from ISMV-infected samples and rapid amplification of cDNA ends (RACE) PCR. The ISMV genome consists of 10,403 nucleotides excluding the poly(A) tail and contains a large open reading frame encoding a polyprotein of 3316 amino acids. Putative proteolytic cleavage sites were identified by BLAST analysis. The ISMV polyprotein showed highest amino acid sequence identity to that encoded by onion yellow dwarf virus. Phylogenetic analysis of the polyprotein amino acid sequence confirmed that ISMV forms a cluster with shallot yellow stripe virus, Cyrtanthus elatus virus A, narcissus degeneration virus and onion yellow dwarf virus. These results confirm that ISMV is a distinct member of the genus Potyvirus.

Bahasa Indonesia

Shallot is an important horticultural crop in Indonesia. One of it’s production constraint is viral disease. Dispersal of viruses on shallots may occurre through shallots bulb trading. However, there is not much information regarding viruses infecting shallot bulbs. Laboratory study was conducted to detect and identify viruses associated with shallot. Random sampling was done for several varieties of shallots (Jawa, Biru, Nganjuk, and Brebes varieties) collected from Bantul Districs. Virus detection and identification was based on RT-PCR using specific primer of OYDV, SYSV, SLV, and ShVX followed by sequencing of the nucleotides. RT-PCR was only successfully amplified Shallot yellow stripe virus (SYSV) with size ~749 bp, while other viruses were not detected. Disease incidence of SYSV on Java and Brebes varieties were 60% and 53.3% respectively. Nucleotide sequences of SYSV CP gene showed the highest homology to SYSV from China and South Korea.Key words: RT-PCR, sequencing nucleotides, Shallot yellow stripe virus

Interaction between potyvirus P3 and ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) of host plants

The P3 protein encoded by Shallot yellow stripe virus onion isolate (SYSV-O) interacted in the Yeast Two-hybrid (Y2H) system and in co-immunoprecipitation (Co-IP) assays with the large subunit of the ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) protein that is encoded by the rbcL gene of its onion host. Dissection analysis by Y2H showed that the main part of SYSV P3 (amino acids 1-390) and onion RbcL (amino acids 1-137) were responsible for the interaction. The P3 proteins encoded by Onion yellow dwarf virus (OYDV), Soybean mosaic virus Pinellia isolate (SMV-P), and Turnip mosaic virus (TuMV) also interacted with RbcL, suggesting that a P3/RbcL interaction might exist generally for potyviruses. An interaction between P3 of these potyviruses and the small subunit of RubisCO (RbcS) was also demonstrated. Moreover, the P3N-PIPO protein encoded by a newly identified open reading frame embedded within the P3 cistron also interacted with both RbcL and RbcS. It is possible that the potyvirus P3 protein affects the normal functions of RubisCO which thus contributes to symptom development.

Protein–protein interactions in two potyviruses using the yeast two-hybrid system

Interactions between all ten mature proteins of the potyviruses Soybean mosaic virus ( Pinellia ternata isolate) and Shallot yellow stripe virus were investigated using yeast two-hybrid (Y2H) assays. Consistently strong self-interactions were found between the pairs of HC-Pro, VPg, NIa-Pro, NIb and CP in both viruses. Apart from the NIb, such interactions have been previously reported for some other potyviruses. The 6K1/NIa-Pro combination gave a consistently moderate to strong interaction in both directions for both viruses. This interaction occurred even when the 6K1 of SMV-P was truncated to eliminate the C-terminal motif that acts as a recognition site for cleavage by the NIa-Pro. Many other interactions occurred only in one direction or only for one of the two viruses. When taken together with other published reports, the data suggest that interactions detected by Y2H should be regarded as only preliminary indications.

A survey of viral diseases ofAlliumcrops in New Zealand

Targeted surveillance was done in 2004/2005 and 2007 to determine the presence of viruses in ornamental and vegetable Allium crops in New Zealand. Several samples were tested for regulated viruses and viruses that commonly infect New Zealand’s Allium crops using enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction. Most viruses were found to occur in mixed infections in garlic, onion, shallot, and in the ornamentals collected from the North and South Islands. New host associations were observed for some viruses previously recorded in New Zealand. Three viruses, Garlic virus A, Iris yellow spot virus and Shallot virus (syn. Shallot mite-borne latent virus), were detected for the first time in New Zealand. However, Impatiens necrotic spot virus, Shallot yellow stripe virus, Sint-Jan’s onion latent virus, Tobacco rattle virus and Tomato black ring virus were not detected in the Allium plants tested. Australasian Plant Pathology Society 2009

Survey for viruses infecting onion, garlic and leek crops in Iran

Surveys to identify virus diseases affecting garlic (Allium sativum), onion (Allium cepa) and Persian leek (Allium ampeloprasum var. persicum) were conducted from 1999 to 2002. Surveys covered different regions of Iran (Tehran [different vegetable markets, farmer fields and cultivation areas], Noushahr, Chalous, Roudbar, Sari, Hamadan, Touyserkan, Ghazvin and Jiroft). A total of 2045 (1285 garlic, 525 onion and 230 leek) samples showing symptoms of virus infection were collected and tested by ELISA; and in some cases tests were also confirmed by immunoelectron microscopy (IEM) for the presence of Allium viruses. ELISA results showed that the following viruses were detected: Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV) (genus Potyvirus, family Potyviridae), Garlic common latent virus (GarCLV), Shallot latent virus (SLV) (genus Carlavirus), Garlic virus D (GarV‐D), Garlic virus B (GarV‐B) and Garlic virus C type (GarV‐C) (genus Allexivirus). None of the samples reacted with antibodies to Shallot yellow stripe virus (SYSV) genus Potyvirus, family Potyviridae), Shallot virus X (ShVX) and Garlic virus A (GarV‐A, genus Allexivirus). GarCLV, SLV, GarV‐D, GarV‐B and GarV‐C are reported for the first time from Allium crops in Iran.

Identification and sequence analysis of potyviruses infecting crops in Vietnam

Fifty-two virus isolates from 13 distinct potyvirus species infecting crops in Vietnam were identified and the 3' region of each genome was sequenced. The viruses were: bean common mosaic virus (BCMV), potato virus Y (PVY), sugarcane mosaic virus (SCMV), sorghum mosaic virus (SrMV), chilli veinal mottle virus (ChiVMV), zucchini yellow mosaic virus (ZYMV), leek yellow stripe virus (LYMV), shallot yellow stripe virus (SYSV), onion yellow dwarf virus (OYDV), turnip mosaic virus (TuMV), dasheen mosaic virus (DsMV), sweet potato feathery mottle virus (SPFMV) and a novel potyvirus infecting chilli, tentatively named chilli ringspot virus (ChiRSV). With the exception of BCMV and PVY, this is first report of these viruses in Vietnam. Further, rabbit bell (Crotalaria anagyroides) and typhonia (Typhonium trilobatum) were identified as new natural hosts of the peanut stunt virus (PStV) strain of BCMV and of DsMV, respectively. Sequence and phylogenetic analyses of the entire CP-coding region revealed considerable variability in BCMV, SCMV, PVY, ZYMV and DsMV.

Improved PCR detection of potyviruses in Allium species

Protocols for producing virus-free Allium plants require an indexing system that is more sensitive than DAS-ELISA and can detect low virus concentrations in infected plants. In the present work, degenerate primers were designed and a one-step IC-RT-PCR protocol was developed to differentiate between Leek yellow stripe virus (LYSV) and Onion yellow dwarf virus (OYDV) in single and mixed infections in several Allium spp. A 566-bp band was observed for LYSV, a 489-bp band for OYDV in single infections, and two bands of the same sizes in mixed infections in different species of Alliaceae. A 508-bp band of Shallot yellow stripe virus and a 594-bp band of Turnip mosaic virus were also amplified with the same primers. RTnested-PCR was also conducted directly in microtitre plate wells after negative or questionable reactions were produced in an ELISA experiment. The detection limit of the DAS-ELISA for LYSV was 16.5– 27.3 ng ml )1 . The RT-nested-PCR done after DAS-ELISA was 10 2 times more sensitive than the DASELISA alone. In parallel, an IC-RT-nested-PCR in microcentrifuge tubes was 10 4 times more sensitive than the DAS-ELISA. The DAS-ELISA-RT-nested-PCR enables the initial screening of samples by DASELISA to eliminate a high percentage of virus-positive plants, considerably reducing the number of plants to analyze further by RT-PCR.

Characterisation of the welsh onion isolate of Shallot yellow stripe virus from China

The host range and nucleotide sequence of shallot yellow stripe virus (SYSV) from welsh onion in Shandong province, China is described. Of the plants tested, only shallot and welsh onion became infected but most shallot plants were symptomless. The complete sequence of one isolate (10429 nt) and the 3'-terminal 3540 nts of a second isolate were determined. They had c. 90% nt identity to one another and to published (partial) sequences of SYSV. SYSV was most closely related to onion yellow dwarf virus (OYDV) and resembled it in having a much larger P3 protein than other species in the genus.

Molecular Characterization of Carla‐ and Potyviruses from Narcissus in China

AbstractConserved carlavirus and potyvirus primers were used in reverse transcriptase‐polymerase chain reaction (RT‐PCR) to amplify virus fragments from Chinese narcissus (Narcissus tazetta var. chinensis) in China and the fragments were subsequently sequenced and compared in phylogenetic analyses. Samples from Fujiang province and Shanghai contained either one or two potyviruses and a carlavirus. One potyvirus (PY1) showed a distant relationship to Iris severe mosaic virus, Onion yellow dwarf virus and Shallot yellow stripe virus, while the other (only in the Fujiang sample, PY2) was most closely related to Turnip mosaic virus (TuMV). Similar experiments using glasshouse grown Narcissus originating from the UK contained Ornithogalum mosaic virus and another potyvirus (PY3) in the TuMV/PY2 cluster. Comparisons with previously determined sequence fragments indicated that PY2 was probably Narcissus yellow stripe virus and PY3 Narcissus late season yellow virus. Carlavirus fragments from both Chinese sites seemed to be of the same virus, which was most closely related in phylogenetic analyses to Potato virus M, Aconitum latent virus and Hop latent virus. It is most probably a new member of the genus Carlavirus and has been tentatively named Narcissus common latent virus.

Characterisation of some carla- and potyviruses from bulb crops in China

Conserved carla- and potyvirus primers were used in RT-PCR to amplify virus fragments from garlic and other bulb crops in China and the fragments were subsequently sequenced and compared in phylogenetic analyses. Garlic plants from Henan, Hubei, Jiangsu, Shangdong and Yunnan provinces all contained at least one isolate each of Garlic latent virus (genus Carlavirus), Onion yellow dwarf virus (OYDV, genus Potyvirus) and Leek yellow stripe virus (LYSV, genus Potyvirus). The complete sequence of a Zhejiang isolate of LYSV was also determined, providing the first complete sequence of this virus. The genome was 10142 nucleotides long excluding the poly(A) tail and had the typical features of the genus Potyvirus, although some of the amino acids surrounding the polyprotein cleavage sites were unusual. Shallot yellow stripe virus (SYSV) was amplified from bunching onion (Allium fistulosum var. caespitosum) in Zhejiang province, providing the first record of SYSV in China. Lily mottle virus was amplified from dragon-teeth lily (Lilium brownii var. viridulum).

Further Evidence that Shallot Yellow Stripe Virus (SYSV) Is a Distinct Potyvirus and Reidentification of Welsh Onion Yellow Stripe Virus as a SYSV Strain

ABSTRACT An antiserum to shallot yellow stripe virus (SYSV) was raised and used in combination with a range of other antisera to potyviruses of Allium spp. in electron microscopic decoration experiments. The serological results corroborated an earlier finding that the type isolates of SYSV and Welsh onion yellow stripe virus (WoYSV) are closely related to each other and only distantly related to onion yellow dwarf (OYDV) and leek yellow stripe (LYSV) viruses, the two other major potyviruses infecting Allium spp. Moreover, the decoration results indicated that Japanese potyviruses named OYDV and Wakegi yellow dwarf virus are isolates of SYSV. Sequence analysis of the 3'-terminal regions of the SYSV and WoYSV ge-nomes revealed coat protein (CP) amino acid and 3'-nontranslated region (3'-NTR) nucleotide sequence identities of 95 and 89%, respectively. The CP amino acid and 3'-NTR nucleotide sequences of these viruses differed from those of OYDV and LYSV by >25 and >67%, respectively. The serological and molecular studies showed that SYSV and WoYSV are different strains of a potyvirus distinct from OYDV and LYSV. For priority reasons, we propose that these strains together with the Wakegi-type isolates of OYDV described in Japan be referred to as SYSV and that SYSV isolates from Allium spp. other than shallot be designated as the Welsh onion strain of SYSV (SYSV-Wo).

Survey and characterization of potyviruses and their strains of Allium species

Nearly 5700 plants of 14 cultivated and 8 wildAllium species and varieties from the Netherlands and other parts of the world, were tested for infection with aphid-borne potyviruses by ELISA, electron microscope decoration tests and/or inoculation onto test plants. This resulted in the detection of two known viruses, viz. leek yellow stripe virus (LYSV) and onion yellow dwarf virus (OYDV), and the discovery and characterization of two new viruses, viz. shallot yellow stripe virus (SYSV) and Welsh onion yellow stripe virus (WoYSV), and of six strains of these viruses. ‘Garlic mosaic’, ‘barlic yellow streak’, ‘onion mosaic’, ‘shallot mosaic’, ‘shallot X’, and ‘shallot yellows’ viruses, incompletely described in the literature, are now reidentified as well-known viruses or as strains or mixtures of such viruses. ‘Garlic yellow stripe virus’ is also a complex containing a potyvirus possibly differing from the viruses found in this survey. The symptoms of the potyviruses studied varied widely and ranged from mild to severe chlorotic to yellow striping of leaves, and they are of little diagnostic importance. LYSV was found in vegetatively propagated pearl onion (A. ampeloprasum var.sectivum) from Europe and Asia. It has decreased in leek crops (A. ampeloprasum var.porrum) in the Netherlands since the 1970, apparently due to resistance in new cultivars. OYDV was common in onion (A. cepa var.cepa) from the former USSR and North Africa, and in European cultivars of shallot (A. cepa var.ascalonicum), with the exception of the highly resistant ‘Sante’, but was not detected during this survey in Asian shallot. European samples of ever-ready onion (A. cepa var.perutile), multiplier onion (A. cepa var.aggregatum) and tree onion (A. cepa var.viviparum) contained OYDV. It was also found in sand leek (A. scorodoprasum) from european gene collections. A strain of OYDV from onion and shallot in Morocco and Spain was virulent on onion and shallot cultivars resistant to common OYDV, as reported early for a similar isolate in the USA. Asian shallot appeared generally infected with the new SYSV, similar to OYDV in host range and symptoms but serologically distinct. It was not detected in onion and shallot from Europe or North Africa. A virulent strain of this virus caused striping in sap-inoculated garlic (A. sativum) and Formosan lily (Lilium formosanum). The new WoYSV, infecting Welsh onion in Indonesia and Japan, was earlier described in Japan as OYDV from rakkyo and Welsh onion. It appeared serologically closely related to SYSV and distantly to OYDV, but differed in its host range. Host-specific strains of LYSV and OYDV were detected in garlic, wild garlic (A. longicuspis), an unidentifiedAllium species (suffix-G), and great-headed garlic (A. ampeloprasum var.holmense) (suffix-GhG)., LYSV-G and OYDV-G infected on average 45% and 73%, respectively, of the garlic samples of worldwide origin. Symptoms of isolates of both strains varied in severity, implying the necessity of serological tests for disease diagnosis and health certification. LYSV-GhG was the cause of yellow striping in 93% of the great-headed garlic plants tested, mainly from the Mediterranean area. One sample was also infected with OYDV-GhG. Many samples from vegetatively propagated crops grown from non-certified planting stock contained a few plants free of potyviruses, implying the possibility to obtain healthy (and possibly resistant) selections of such cultivars avoiding meristem-tip culture. Cross-protection of garlic sets by a mild potyvirus isolate seems to be an alternative to the use of vulnerable virus-free sets. Generally, viruses and virus strains could not be transmitted to anyAllium species other than their natural host, except to the highly susceptible crow garlic (A. vineale). This species, and other predominantly vegetatively propagating wildAllium spp. (field garlic,A. oleraceum; ramsons,A. ursinum; sand leek), were found not to be reservoirs of viruses that might infectAllium crops in the netherlands. Streaking in vegetatively propagated wild leeks (A. ampeloprasum and closely related species) originating from the Mediterranean area and Asia was due to an undescribed miteborne virus. The survey confirmed that spread of potyviruses inAllium crops in the Netherlands is from planting sets, and from a neighbouring crop only if of the same species.