Comparative mapping of ZYMV resistances in cucumber (Cucumis sativus L.) and melon (Cucumis melo L.)

Zucchini yellow mosaic virus (ZYMV) routinely causes significant losses in cucumber (Cucumis sativus L.) and melon (Cucumis melo L.). ZYMV resistances from the cucumber population TMG1 and the melon plant introduction (PI) 414723 show different modes of inheritance and their genetic relationships are unknown. We used molecular markers tightly linked to ZYMV resistances from cucumber and melon for comparative mapping. A 5-kb genomic region (YCZ-5) cosegregating with the zym locus of cucumber was cloned and sequenced to reveal single nucleotide polymorphisms and indels distinguishing alleles from ZYMV-resistant (TMG1) and susceptible (Straight 8) cucumbers. A low-copy region of the YCZ-5 clone was hybridized to bacterial artificial chromosome (BAC) clones of melon and a 180-kb contig assembled. One end of this melon contig was mapped in cucumber and cosegregated with ZYMV resistance, demonstrating that physically linked regions in melon show genetic linkage in cucumber. However the YCZ-5 region segregated independently of ZYMV resistance loci in two melon families. These results establish that these sources of ZYMV resistances from cucumber TMG1 and melon PI414723 are likely non-syntenic.     

A genetic map of cucumber composed of RAPDs, RFLPs, AFLPs, and loci conditioning resistance to papaya ringspot and zucchini yellow mosaic viruses.

The watermelon strain of papaya ringspot virus (PRSV-W) and zucchini yellow mosaic virus (ZYMV) are potyviruses that cause significant disease losses in cucumber. Resistances have been identified primarily in exotic germplasm that require transfer to elite cultivated backgrounds. To select more efficiently for virus resistances, we identified molecular markers tightly linked to PRSV-W and ZYMV resistances in cucumber. We generated F6 recombinant inbred lines (RILs) from a cross between Cucumis sativus L. 'Straight 8' and a line from 'Taichung Mou Gua', TMG1 (susceptible and resistant, respectively, to both viruses), and studied the segregations of amplified fragment length polymorphism (AFLP) markers, randomly amplified polymorphic DNAs (RAPDs), restriction fragment length polymorphisms (RFLPs), and resistances to PRSV-W and ZYMV. A 353-point map of cucumber was generated, delineating 12 linkage groups at LOD 3.5. Linkage arrangements among RFLPs were consistent with previously published maps; however linkages among RAPDs in our map did not agree with a previously published map. Resistances to PRSV-W and ZYMV were tightly linked (2.2 cM) and mapped to the end of one linkage group. One AFLP cosegregated with resistance to ZYMV.     

Inheritance of resistance to watermelon mosaic virus in the cucumber line TMG-1: tissue-specific expression and relationship to zucchini yellow mosaic virus resistance

The inbred cucumber (Cucumis sativus L.) line TMG-1 is resistant to three potyviruses:zucchini yellow mosaic virus (ZYMV), watermelon mosaic virus (WMV), and the watermelon strain of papaya ringspot virus (PRSV-W). The genetics of resistance to WMV and the relationship of WMV resistance to ZYMV resistance were examined. TMG-1 was crossed with WI-2757, a susceptible inbred line. F₁, F₂ and backcross progeny populations were screened for resistance to WMV and/or ZYMV. Two independently assorting factors conferred resistance to WMV. One resistance was conferred by a single recessive gene from TMG-1 (wmv-2). The second resistance was conferred by an epistatic interaction between a second recessive gene from TMG-1 (wmv-3) and either a dominant gene from WI-2757 (Wmv-4) or a third recessive gene from TMG-1 (wmv-4) located 20–30 cM from wmv-3. The two resistances exhibited tissue-specific expression. Resistance conferred by wmv-2 was expressed in the cotyledons and throughout the plant. Resistance conferred by wmv-3 + Wmv-4 (or wmv-4) was expressed only in true leaves. The gene conferring resistance to ZYMV appeared to be the same as, or tightly linked to one of the WMV resistance genes, wmv-3.     

Reactions of some cucurbitaceous species Tozucchini yellow mosaic virus (ZYMV)

Zucchini yellow mosaic virus (ZYMV) is a widespread serious pathogen of cucurbitaceous plants. ZYMV was first detected in Hungary in 1995. Since then it has become one of the most dangerous viruses of the Cucurbitaceae family causing serious epidemics. The virus has many hosts, which - particularly perennial ones - may play important role as virus reservoirs and infection sources in virus epidemiology. On the other hand wild weed species maybe sources of resistance to viruses. Our research was carried out on a total of 15 wild species from 8 genera (Cucumis, Cucurbita, Cyclanthera, Ecballium Momordica, Lagenaria, Zehneria, Bryonia). Test plants were mechanically inoculated with ZYMV. Local and systemic symptoms were determined and 5 weeks after inoculation DAS-ELISA tests were also carried out. Symptomless plants were reinoculated to Cucumis sativus cv. Accordia test plants. On the basis of the results we determined the percentages of infections and so we classified the test-plants into sensitive and resistance categories. On the basis of the results new host plants of ZYMV are the followings: Bryonia dioica, Cyclanthera pedata, Ecballium elaterium, Momordica balsamina, Momordica rostrata, and Zehneria scabra. Among them Momordica balsamina and Ecballium elaterium showed latent to ZYMV. Bryonia alba and Zehneria indica are especially remarkable, because they proved resistant to ZYMV on the basis of symptomatology and serology. Our results might have significant role in the field of research of host range, virus resistance and virus differentiation.     

Multiple alleles for zucchini yellow mosaic virus resistance at the zym locus in cucumber

 Sources of resistance to several potyviruses have been identified and characterized within the cucumber (Cucumis sativus L.) germplasm. Resistance to zucchini yellow mosaic virus (ZYMV) is present in inbred lines derived from the Dutch hybrid Dina (Dina-1) and from the Chinese cultivar ‘Taichung Mou Gua’ (TMG-1). Tests of allelism indicated that the genes for resistance to ZYMV in TMG-1 and Dina-1 are at the same locus; however, the two genotypes exhibited different phenotypes in response to cotyledon inoculation with ZYMV. Dina-1 exhibited a distinct veinal chlorosis and accumulation of virus limited to the first and/or second true leaves, while TMG-1 remained symptom-free and did not accumulate virus. The distinct veinal chlorosis phenotype in Dina-1 was dominant to the symptom-free phenotype in TMG-1 and was shown not to be due to a separate gene. These results indicate that a series of alleles differing in effectiveness and dominance relationships occurs at the zym locus such that Zym>zym ^Dina>zym ^TMG-1. In addition to ZYMV resistance, TMG-1 is also resistant to watermelon mosaic virus (WMV), the watermelon strain of papaya ringspot virus (PRSV-W) and the Moroccan watermelon mosaic virus (MWMV); the WMV and MWMV resistances are at the same locus, or tightly linked to the zym locus. Dina-1 also was found to be resistant to PRSV-W and MWMV. The gene for MWMV resistance in Dina-1 appeared to be at the same locus or tightly linked (<1% recombination) to the gene for ZYMV resistance. In contrast to the response to ZYMV inoculation, Dina-1 does not exhibit distinct veinal chlorosis when inoculated with PRSV-W or MWMV. Collectively, these observations suggest that the gene(s) conferring resistance to ZYMV, WMV, and MWMV may be part of a gene cluster for potyvirus resistance in cucumber. Received: 12 November 1996 / Accepted: 25 April 1997     

Genetic Variability of Fusarium oxysporum f.sp. ciceris Population Affecting Chickpea in the Sudan

Fusarium wilt caused by Fusarium oxysporum f.sp. ciceris (Foc) is the most important soilborne disease of chickpea in the Sudan and many other countries. A total of 76 Foc isolates from six different chickpea‐growing states in the Sudan have been collected in this study to investigate the genetic diversity of Sudanese Foc isolates. Additional 14 Foc isolates from Syria and Lebanon were included in this study. All isolates were characterized using four random amplified polymorphic DNA (RAPD), three simple sequence repeats (SSR), five sequence‐characterized amplified region (SCAR) primers and three specific Foc genome primers. Based on the similarity coefficient, the results indicated two major clusters included seven subclusters. The isolates from the Sudan were grouped as identified as races 0, 2 and unknown races. The isolates from Syria and Lebanon were grouped together as they identified as races 1B/C and 6, respectively. This study identified a new race Foc (race 0) in the Sudan. The results of this study will be useful for breeders to design effective resistance breeding program in chickpea in the Sudan.     

Melon RNA interference (RNAi) lines silenced for Cm-eIF4E show broad virus resistance

Efficient and sustainable control of plant viruses may be achieved using genetically resistant crop varieties, although resistance genes are not always available for each pathogen; in this regard, the identification of new genes that are able to confer broad-spectrum and durable resistance is highly desirable. Recently, the cloning and characterization of recessive resistance genes from different plant species has pointed towards eukaryotic translation initiation factors (eIF) of the 4E family as factors required for the multiplication of many different viruses. Thus, we hypothesized that eIF4E may control the susceptibility of melon (Cucumis melo L.) to a broad range of viruses. To test this hypothesis, Cm-eIF4E knockdown melon plants were generated by the transformation of explants with a construct that was designed to induce the silencing of this gene, and the plants from T2 generations were genetically and phenotypically characterized. In transformed plants, Cm-eIF4E was specifically silenced, as identified by the decreased accumulation of Cm-eIF4E mRNA and the appearance of small interfering RNAs derived from the transgene, whereas the Cm-eIF(iso)4E mRNA levels remained unaffected. We challenged these transgenic melon plants with eight agronomically important melon-infecting viruses, and identified that they were resistant to Cucumber vein yellowing virus (CVYV), Melon necrotic spot virus (MNSV), Moroccan watermelon mosaic virus (MWMV) and Zucchini yellow mosaic virus (ZYMV), indicating that Cm-eIF4E controls melon susceptibility to these four viruses. Therefore, Cm-eIF4E is an efficient target for the identification of new resistance alleles able to confer broad-spectrum virus resistance in melon.     

金瓜和白瓜花叶病毒病病原的初步鉴定

崇明是上海出口蔬菜生产基地之一,也是国家级的绿色食品园区之一,具有生产绿色蔬菜商品的生态环境和资源优势。特色出口蔬菜金瓜(Cucurbita pepo L.var.ovifera)、白瓜(Cucumis melo L.var.conomon,又名盐渍菜瓜)1997～1999统计病毒病发病率为23％,被感染的金瓜、白瓜田     

Leishmania donovani: Genetic diversity of isolates from Sudan characterized by PCR-based RAPD

Drug unresponsiveness in patients with visceral leishmaniasis (VL) is a problem in many endemic areas. This study aimed to determine genetic diversity of Leishmania donovani isolates from a VL endemic area in Sudan as a possible explanation for drug unresponsiveness in some patients. Thirty clinically stibogluconate (SSG)-sensitive isolates were made SSG-unresponsive in vitro by gradually increasing SSG concentrations. The sensitive isolates and their SSG-unresponsive counterparts were typed using mini-circle kDNA and categorized using PCR-RAPD. All the isolates were typed as L. donovani, the resulting PCR-RAPD characterization of the SSG-sensitive isolates gave three distinct primary genotypes while, the SSG-unresponsive isolates showed only a single band. L. donovani isolates from eastern Sudan are diverse; this probably resulted from emergence of new L. donovani strains during epidemics due to the pressure of widespread use of antimonials.In this communication the possible role of isolates diversity in antimonial unresponsiveness and the in vitro changing PCR-RAPD band pattern in SSG-unresponsive strains were discussed.     

Distribution of legionellae in a hospital water system: prevalence of immunologically and genetically related Legionella pneumophila serogroup 6 isolates

A hospital warm water system was monitored for the presence and distribution of legionellae. Subtyping of ten selected Legionella pneumophila isolates, originating from four different sites in the system by using serogroup specific antisera in an indirect immunofluorescence test, revealed that nine of the ten isolates belong to serogroup 6, while the remaining one was serogroup 10. Two monoclonal antibodies (mAbs) specific for a subgroup of serogroup 6 strains were further used for characterization. None of the strains reacted with these mAbs. Genome analysis by elaborating NotI profiles using the pulsed field gel electrophoresis (PFGE) technique revealed that nearly all serogroup 6 isolates derived from different sites, including a new building connected by a ring pipe, were identical according to restriction fragment patterns. The patterns were distinguishable from those of the two L. pneumophila serogroup 6 reference strains, and from that of the L. pneumophila serogroup 10 isolate. These data argue for a relatively homogeneous L. pneumophila serogroup 6 population in the entire water system.     

The heterogeneity of phloem exudate proteins from different plants: A comparative survey of ten plants using polyacrylamide gel electrophoresis

Summary Proteins in sieve tube exudate from Ricinus communis L., Acer pseudoplatanus L., Aesculus hippocastanum L., Cucumis melo L., and two cultivars each of Cucumis sativus L., Cucurbita pepo L. and Cucurbita maxima Duchesne were fractionated and compared using polyacrylamide gel electrophoresis. Striking differences in major exudate proteins were displayed among the genera and species examined. Even cultivars within a single species, although showing general similarities, differed in some prominent proteins. Estimated molecular weights of the major exudate proteins from each plant are presented. The effects of reducing and chaotropic agents on the aggregation and subunit composition of exudate proteins from Cucumis sativus have been investigated. The problems involved in relating structure, function and biochemistry of P-protein are discussed.     

小西葫芦黄化花叶病毒分离物的3′末端序列多态性研究

研究了来自中国大陆9个小西葫芦黄化花叶病毒（ZYMV）分离物的基因组3′末端核苷酸序列及所推导的外壳蛋白（CP）氨基酸序列以及3′末端非编码区（UTR）序列,并与其它地区所报道的16个ZMYV分离物进行了同源性比较。ZYMV CP基因核苷酸序列具有一定的寄主相关性和地域相关性,但总体上其关联程度不明显;同时,CP氨基酸序列的寄主适应性程度明显高于地域相关性。25个ZYMV分离物的CP氨基酸序列根据其变异程度分为2个区： N端约41个氨基酸为高度变异区,CP核心区和C端氨基酸序列为保守区。研究结果初步揭示了ZYMV作为单链RNA病毒通过与寄主相互作用而表现寄主适应性变异的趋势。     

Characterization of sources of resistance to the watermelon strain of Papaya ringspot virus in cucumber: allelism and co-segregation with other potyvirus resistances

At least three sources of resistance to the watermelon strain of Papaya ringspot virus (PRSV-W) have been identified in cucumber (Cucumis sativus L.) including: ’TMG-1’, an inbred line derived from the Taiwanese cultivar, ’Taichung Mou Gua’; ’Dina-1’, an inbred line derived from the Dutch hybrid ’Dina’; and the South American cultivar ’Surinam’. In this investigation we sought to determine the inheritance of resistance to PRSV-W in ’Dina-1’, the allelic relationships among the three sources of PRSV-W resistance, and the relationship between PRSV-W resistance and known resistances to other cucurbit potyviruses. Like ’Surinam’ and ’TMG-1’, resistance in ’Dina-1’ is controlled by a single gene. Despite differences in dominance vs recessive performance and patterns of virus accumulation, all three sources of resistance complemented each other. ’TMG-1’ and ’Dina-1’ also possess co-segregating, single-gene resistances to Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus and Moroccan watermelon mosaic virus. Sequential inoculations and F₃ family analysis indicated that resistance to PRSV-W completely co- segregated with resistance to ZYMV in ’TMG-1’. Although PRSV-W resistances are at the same locus in both ’TMG-1’ and ’Surinam’, ’Surinam’ is only resistant to PRSV-W, and progeny of ’TMG-1’×’Surinam’ were resistant to PRSV-W but susceptible to ZYMV. Susceptibility to ZYMV and resistance to PRSV-W in ’Surinam’ was not influenced by co-inoculation or sequential in- oculations of the two viruses. Collectively, the co- segregation of resistances to PRSV-W, ZYMV, WMV and MWMV in ’TMG-1’ (within 1 cM), allelism of PRSV-W resistances in ’TMG-1’ and ’Surinam’, and resistance to only PRSV-W in ’Surinam’, suggest that multiple potyvirus resistance in cucumber may be due to different alleles of a single potyvirus resistance gene with differing viral specificities, or that the multiple resistances are conferred by a tightly linked cluster of resistance genes, of which ’Surinam’ only possesses one member. Received: 22 July 1999 / Accepted: 2 December 1999     

Quantitative analysis of resistance in cotton to three new isolates of the bacterial blight pathogen

Summary Genetic variability for virulence of the bacterial blight pathogen [Xanthomonas campestris pv malvacearum (Smith) Dye] on cotton (Gossypium hirsutum L.) has been shown by the identification of 19 races of the pathogen based on disease reactions of a set of ten host differentials. This study was conducted to determine the inheritance of host resistance to three recently identified isolates of X. campestris pv malvacearum, which are virulent on the entire set of differentials. True leaves of Tamcot CAMD-E, LEBOCAS-3-80, Stoneville 825, and their f₁, F₂, and backcross progenies were wound-inoculated in the field with separate bacterial suspensions of the virulent HV3, HV7, and Sudan isolates of the pathogen. LEBOCAS-3-80 was replaced with S295, a new immune cultivar, for a greenhouse study in which both cotyledons and true leaves were inoculated. Disease reactions were rated on a scale of 1–10, and genetic models were proposed utilizing generation means analysis. Dominance, when significant, was in the direction of resistance in all but one cross-isolate combination. Digenic interaction components indicated a duplicate type. Narrow-sense heritability for resistance ranged from 0.59 to 0.68; therefore, primarily additive-genetic variability among the selected cutlivars was detected, indicating that breeding for improved resistance to these isolates is a practical goal.Contribution of the Department of Soil and Crop Sciences and the Texas Agricultural Experiment Station     

Serological diagnosis and host range studies of important viral diseases of a few cucurbitaceous crops in Maharashtra,India

Around 39 well characterised viruses affect cucurbits crops in developing countries and their viral diversity may be the consequence for genetic and ecological diversity of their hosts. Indeed, cucurbits are grown in variety of climatic, environmental and agricultural conditions, and this may provide more or less favourable conditions for the specific viruses or their hosts. The presence of various viral diseases caused by different viruses in Maharashtra was studied from the infected samples collected from cucurbits and melons during the survey conducted in 2009–2010 in different locations. The virus isolates collected from various cucurbitaceous crops were established and their host ranges were studied by sap transmission. The study revealed Cucumber Mosaic Virus (CMV), Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV) and Cucumber green mottle mosaic virus infections predominately found in Nashik region, and Watermelon bud necrosis virus (WBNV), CMV, ZYMV, WMV and Watermelon silver mottle virus (WSMoV) infections in Aurangabad and Paithan regions. In Sangamner region, the crop was mostly affected by WBNV, ZYMV and WSMoV, and CMV was found only in Sillod region. The protocols for performing sap transmission tests in assay hosts were standardised for ZYMV, CMV and WBNV. Using direct antigen-coating enzyme-linked immunosorbent assay, of all the plant parts, young leaves were found to have high concentration of virus and suitable for virus detection in screening programmes. CMV and ZYMV was found to have high concentration of virus and suitable for virus detection in screening programmes.     

Inheritance analysis and identification of SNP markers associated with ZYMV resistance in <Emphasis Type="Italic">Cucurbita pepo</Emphasis>

Cucurbit crops are economically important worldwide. One of the most serious threats to cucurbit production is Zucchini yellow mosaic virus (ZYMV). Several resistant accessions were identified in Cucurbita moschata and their resistance was introgressed into Cucurbita pepo. However, the mode of inheritance of ZYMV resistance in C. pepo presents a great challenge to attempts at introgressing resistance into elite germplasm. The main goal of this work was to analyze the inheritance of ZYMV resistance and to identify markers associated with genes conferring resistance. An Illumina GoldenGate assay allowed us to assess polymorphism among nine squash genotypes and to discover six polymorphic single-nucleotide polymorphisms (SNPs) between two near-isogenic lines, “True French” (susceptible to ZYMV) and Accession 381e (resistant to ZYMV). Two F₂ and three BC₁ populations obtained from crossing the ZYMV-resistant Accession 381e with two susceptible ones, the zucchini True French and the cocozelle “San Pasquale,” were assayed for ZYMV resistance. Molecular analysis revealed an approximately 90% association between SNP1 and resistance, which was confirmed using High Resolution Melt (HRM) and a CAPS marker. Co-segregation up to 72% in populations segregating for resistance was observed for two other SNP markers that could be potentially linked to genes involved in resistance expression. A functional prediction of proteins involved in the resistance response was performed on genome scaffolds containing the three SNPs of interest. Indeed, 16 full-length pathogen recognition genes (PRGs) were identified around the three SNP markers. In particular, we discovered that two nucleotide-binding site leucine-rich repeat (NBS-LRR) protein-encoding genes were located near the SNP1 marker. The investigation of ZYMV resistance in squash populations and the genomic analysis performed in this work could be useful for better directing the introgression of disease resistance into elite C. pepo germplasm.     

Diverse viscerotropic isolates of Leishmania all express a highly conserved secretory nuclease during human infections

Previously, we characterized a gene encoding the unique nuclease (LdNuc(s)) from a Sudanese isolate of the human pathogen Leishmania donovani. This parasite secretory enzyme is involved in the salvage of host-derived purines and is constitutively expressed by both developmental forms of the parasite. Currently, we assessed whether an LdNuc(s)-like nuclease was conserved among other geographically disparate isolates of L. donovani and whether this enzyme was produced by intracellular amastigotes during human infections. Using RT-PCR and Southern blotting, we showed that LdNuc(s) gene homologs were present in each of the viscerotropic Leishmania tested (i.e., L. donovani isolates from the Sudan, Ethiopia and India as well as L. infantum). Further results of in situ enzyme activity gel analyses showed that each of these parasite isolates also expressed a released/secreted LdNuc(s)-like nuclease activity. In Western blots, our anti-LdNuc(s) (Sudan) peptide-specific antibody reacted with only a single ~35 kDa protein in each of the viscerotropic Leishmania isolates. Further, the ~35 kDa nuclease secreted by each of these isolates was specifically immunoprecipitated by the anti-LdNuc(s) antibody above. In situ gel analyses showed that each of these immunoprecipitates had LdNuc(s)-like nuclease activity. Moreover, sera from acute visceral leishmaniasis patients from India, Sudan and Brazil all immunoprecipitated an LdNuc(s)-HA expressed nuclease demonstrating, that these patients possessed antibodies against this parasite secretory enzyme. Cumulatively, these results showed that the LdNuc(s) homologs were functionally conserved among geographically disparate visceral Leishmania spp. and that amastigotes of these parasites must produce this nuclease enzyme during the course of human disease.     

Differentiation of Yam Virus Isolates Using Symptomatology, Western Blot Assay, and Monoclonal Antibodies

Monoclonal antibodies (mAbs) were prepared against a yam mosaic virus (YMV) isolate from the Côte d'Ivoire. Symptomatology, Western immunoblotting, and ELISA were used to discriminate 69 isolates of YMV originating from different Dioscorea species and from various yam producing areas. These isolates induced two types of symptoms, were of four different electrophoretic mobilities and formed two serogroups. These results suggest that at least six differetit groups of isolates exist, three of which infect the main cultivated species in various geographical areas while two others were from unusual samples in our collection. An isolate from 'Pilimpikou Yam' from Central Burkina Faso was serologically distinct. It is concluded that there is a significant variability among yam virus isolates which is unrelated to the origin of the isolate (geographic or host species). It is suggested that precautions should be taken in order to avoid international exchange of infected material.     

Relative incidence,spatial distribution and genetic diversity of cucurbit viruses in eastern Spain

Viral diseases that could cause important economic losses often affect cucurbits, but only limited information on the incidence and spatial distribution of specific viruses is currently available. During the 2005 and 2006 growing seasons, systematic surveys were carried out in open field melon (Cucumis melo), squash and pumpkin (Cucurbita pepo), watermelon (Citrullus lanatus) and cucumber (Cucumis sativus) crops of the Spanish Community of Valencia (eastern Spain), where several counties have a long standing tradition of cucurbit cultivation and production. Surveyed fields were chosen with no previous information as to their sanitation status, and samples were taken from plants that showed virus‐like symptoms. Samples were analysed using molecular hybridisation to detect Beet pseudo‐yellows virus (BPYV), Cucurbit aphid‐borne yellows virus (CABYV), Cucumber mosaic virus (CMV), Cucumber vein yellowing virus (CVYV), Cucurbit yellow stunting disorder virus (CYSDV), Melon necrotic spot virus (MNSV), Papaya ring spot virus (PRSV), Watermelon mosaic virus (WMV) and Zucchini yellow mosaic virus (ZYMV). We collected 1767 samples from 122 independent field plots; out of these, approximately 94% of the samples were infected by at least one of these viruses. Percentages for the more frequently detected viruses were 35.8%, 27.0%, 16.5% and 7.2% for CABYV, WMV, PRSV and ZYMV, respectively, and significant deviations were found on the frequency distributions based on either the area or the host sampled. The number of multiple infections was high (average 36%), particularly for squash (more than 57%), with the most frequent combination being WMV + PRSV (12%) followed by WMV + CABYV (10%). Sequencing of WMV complementary DNA suggested that ‘emerging’ isolates have replaced the ‘classic’ ones, as described in southern regions of France, leading us to believe that cucurbit cultivation could be severely affected by these new, emerging isolates.