Cucurbit Yellow Stunting Disorder Virus Research Articles

Molecular characterization of Criniviruess involved in the etiology of cucumber yellowing disease in Riyadh region, Saudi Arabia

During the growing seasons 2014 and 2015, 134 cucumber and 103 weed samples showing typical yellowing diseases symptoms accompanied by chlorotic spots and interveinal chlorosis were collected from Riyadh region, Saudi Arabia. For this reason, RT-PCR was conducted for detection of two criniviruses, Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV) which are implicated in cucurbit yellows disease. Results showed the presence of CCYV and CYSDV in cucumber samples in 61.1% and 19.4%, respectively, whereas 9% of the plants were contained mixed infection. In addition, four weed species were identified, for the first time, as alternative hosts of CCYV; whereas CYSDV was reported only in Malva parviflora plants. Partial nucleotide sequencing analysis was conducted using 13 CCYV and five of CYSDV isolates originated from cucumber and wild hosts. Both viruses exhibited low genetic diversity; however, phylogenetic analysis clustered the obtained CYSDV isolates in a separated group, named the “Eastern subpopulation”, while CCYV isolates were classified into subgroups IIa and IIb, among other published sequences, forming a different evolutionary lineage from group I, which contained an isolate from Iran.

Field evaluation of Cucurbit yellow stunting disorder virus transmission by Bemisia tabaci

Cucurbit yellow stunting disorder virus (CYSDV) is a whitefly-transmitted Crinivirus (Closteroviridae) that impacts melon production in many parts of the world including the USA. It has been responsible for melon crop loss in the southwestern U.S. since 2006 when it was first identified. Control strategies have revolved mainly around chemical control, but research to identify suitable products and approaches to implementing them have lagged. The current study investigated the performance of four systemic insecticides in the field while concurrently tracking CYSDV disease progression after controlled and natural whitefly inoculation of young melon plants. Assessments of virus incidence were made using two different visual observation methods in concert with ELISA analyses of leaf disks samples collected biweekly. Infection rates were consistently lowest in plots treated with the butenolide insecticide flupyradifurone while dinotefuran was second in efficacy measures. Flupyradifurone also held whitefly densities to their lowest numbers relative to the other treatments. Two other insecticides, imidacloprid and cyantraniliprole, exacerbated virus incidence in multiple trials. Further investigation into the anomalous finding of increased virus incidence due to insecticide application is ongoing.

Effects of foliar and systemic insecticides on whitefly transmission and incidence of Cucurbit yellow stunting disorder virus.

Cucurbit yellow stunting disorder virus (CYSDV) is a cosmopolitan viral disease transmitted by Bemisia tabaci that infects cucurbit crops. Cantaloupe production in the southwestern USA has been confronted by epidemics of CYSDV since 2006 when it was first identified in Arizona and California. As a phloem-limited virus that is vectored in a semi-persistent manner by B. tabaci, CYSDV has transmission characteristics that may be suppressed by select insecticide applications. Eight active ingredients formulated as foliar and/or soil-applied insecticides were tested to determine the suppressive effect on transmission and incidence of CYSDV in greenhouse and field studies. Many compounds limited virus transmission to <10% infected plants even when challenged by 30 viruliferous whiteflies. Foliar formulations had greater knockdown activity than their soil-applied analogs and resulted in lower virus transmission. Insecticides that had the greatest effect on reducing virus transmission in the greenhouse also showed the lowest incidence of CYSDV in field trials. Select insecticides can significantly reduce transmission of CYSDV. However, insecticide management of CYSDV incidence in cantaloupes has limitations in chronically high infestation areas such as the southwestern USA, and is often only able to delay disease onset rather than prevent its occurrence. © 2016 Society of Chemical Industry.

First report of Cucurbit yellow stunting disorder virus infecting cucurbits in Italy

In June 2016, a survey was conducted in Sardinia, Italy to study the variability of cucurbit viral populations in melon ( Cucumis melo var. cantalupo and C. melo var. inodorus ) and zucchini ( Cucurbita pepo ). Two main cucurbit-growing…

In Vitro Synthesized RNA Generated from cDNA Clones of Both Genomic Components of Cucurbit yellow stunting disorder virus Replicates in Cucumber Protoplasts.

Cucurbit yellow stunting disorder virus (CYSDV), a bipartite whitefly-transmitted virus, constitutes a major threat to commercial cucurbit production worldwide. Here, construction of full-length CYSDV RNA1 and RNA2 cDNA clones allowed the in vitro synthesis of RNA transcripts able to replicate in cucumber protoplasts. CYSDV RNA1 proved competent for replication; transcription of both polarities of the genomic RNA was detectable 24 h post inoculation. Hybridization of total RNA extracted from transfected protoplasts or from naturally CYSDV-infected cucurbits revealed high-level transcription of the p22 subgenomic RNA species. Replication of CYSDV RNA2 following co-transfection with RNA1 was also observed, with similar transcription kinetics. A CYSDV RNA2 cDNA clone (T3CM8Δ) comprising the 5′- and 3′-UTRs plus the 3′-terminal gene, generated a 2.8 kb RNA able to replicate to high levels in protoplasts in the presence of CYSDV RNA1. The clone T3CM8Δ will facilitate reverse genetics studies of CYSDV gene function and RNA replication determinants.

Cucurbit yellow stunting disorder virus. [Distribution map

Abstract A new distribution map is provided for Cucurbit yellow stunting disorder virus. Closteroviridae: Crinivirus. Hosts: Cucurbitaceae, especially melon ( Cucumis melo ), watermelon ( Citrullus lanatus ) and cucumber ( Cucumis sativus ). Information is given on the geographical distribution in Europe (Cyprus, France, Greece, Crete, Mainland Greece, Portugal, Spain, Canary Islands and Mainland Spain), Asia (China, Jiangsu, Zhejiang, Iran, Israel, Jordan, Lebanon, Saudi Arabia, Syria, Turkey and United Arab Emirates), Africa (Egypt, Morocco, Sudan and Tunisia), North America (Mexico, USA, Arizona, California, Florida and Texas) and Central America and Caribbean (Guatemala).

Control of Sweetpotato Whitefly Adults with Foliar Neonicotinoid Insecticides in Spring Cantaloupes, 2014

With the loss of the endosulfan on melons, this trial was designed to evaluate the efficacy of several neonicotinoid alternatives against adult sweetpotato whiteflies and the associated incidence of cucurbit yellow stunting disorder virus (CYSDV) in spring melons. Cantaloupe plots planted with ‘Sol Dorado’ were established at the Yuma Agricultural Center on 20 March, 2014, and managed similarly to local growing practices. Plots consisted of a 84-inch bed, 45-ft-long with a 7-ft buffer between each plot. The study was designed as a randomized complete block design with four replicates per treatment. Product formulations and rates are shown in Tables 1 and 2. Three foliar spray applications were applied on 29 April …

Host-Specific Relationship Between Virus Titer and Whitefly Transmission of Cucurbit yellow stunting disorder virus.

Cucurbit yellow stunting disorder virus (CYSDV; genus Crinivirus, family Closteroviridae) was identified in the melon (Cucumis melo) production regions of the desert southwestern United States in fall 2006. It is now well established in the region, where it is transmitted efficiently by the sweet potato whitefly, Bemisia tabaci biotype B (MEAM1). In order to evaluate the spread and establishment of the virus, nearly all spring and fall cucurbit fields planted in the Imperial Valley of California from 2007 to 2009 were surveyed and representative plants were tested for CYSDV infection. Incidence of CYSDV in spring melon fields was initially low and limited to a small number of fields in 2007 but increased to 63% of fields by spring 2009. Virus incidence in fall melon fields was 100% in each year. These results suggested that the virus had become established in native vegetation, weeds, and other crop species, and represented an increasing threat to melon production in the southwestern United States. Therefore, a select set of weed and crop species which grow or are cultivated in the Imperial Valley were evaluated as CYSDV reservoir hosts. For each species, we determined the capacity of CYSDV to accumulate, the relationship between virus titer in these source plants and transmission by whiteflies, as well as subsequent accumulation in inoculated cucurbit plants. Among these hosts, there was considerable variation in virus accumulation and transmission rates. Cucurbit hosts had the highest CYSDV titers, were efficient sources for virus acquisition, and showed a positive correlation between titer in source plants and transmission. Noncucurbit hosts had significantly lower CYSDV titers and varied in their capacity to serve as sources for transmission. CYSDV titers in some noncucurbit source plants, specifically common bean (Phaseolus vulgaris) and shepherd's purse (Capsella bursa-pastoris), were not positively correlated with transmission, demonstrating that additional environmental, physical, or biochemical factors were involved. These results demonstrate that multiple factors influence the efficiency with which a host plant species will be a reservoir for vector transmission of virus to crops.

First Report of Cucurbit chlorotic yellows virus in Cucumber in Saudi Arabia

HomePlant DiseaseVol. 99, No. 5First Report of Cucurbit chlorotic yellows virus in Cucumber in Saudi Arabia PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Cucurbit chlorotic yellows virus in Cucumber in Saudi ArabiaM. A. Al-Saleh, I. M. Al-Shahwan, M. A. Amer, M. T. Shakeel, O. A. Abdalla, C. G. Orfanidou, and N. I. KatisM. A. Al-SalehSearch for more papers by this author, I. M. Al-ShahwanSearch for more papers by this author, M. A. AmerSearch for more papers by this author, M. T. ShakeelSearch for more papers by this author, O. A. AbdallaSearch for more papers by this author, C. G. OrfanidouSearch for more papers by this author, and N. I. KatisSearch for more papers by this authorAffiliationsAuthors and Affiliations M. A. Al-Saleh I. M. Al-Shahwan M. A. Amer M. T. Shakeel O. A. Abdalla , Plant Protection Department, College of Food and Agriculture Sciences, King Saud University, Riyadh 11451, Saudi Arabia C. G. Orfanidou N. I. Katis , Aristotle University of Thessaloniki, School of Agriculture, Forestry and Natural Environment, Faculty of Agriculture, Plant Pathology Lab, Thessaloniki 54124, Greece. Published Online:29 May 2015https://doi.org/10.1094/PDIS-11-14-1101-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat In March 2014, a total of 27 samples of cucumber plants showing interveinal chlorotic spots on lower leaves were collected from two greenhouses in the Al-Kharj area of Riyadh, Saudi Arabia. Affected plants were heavily infested with dense populations of Bemisia tabaci biotype B whereas aphid colonies, mainly Aphis gossypii, were rather rare. Yellowing disorder is reported to be caused primarily by four different viruses: Beet pseudo-yellows virus (BPYV), Cucurbit yellow stunting disorder virus (CYSDV), Cucurbit chlorotic yellows virus (CCYV), and Cucurbit aphid-borne yellows virus (CABYV). In order to identify the etiology of the disease, total RNA was extracted from all collected samples (Chatzinasiou et al. 2010) and RT-PCR was performed suing primers specific to each virus. (Boubourakas et al. 2006; Lotos et al. 2014; Orfanidou et al. 2014). Results showed the presence of CCYV in both greenhouses (13/27), while a relatively high proportion of samples were also infected with CYSDV (11/27) and CABYV (8/27). Dual mixed infections were observed in almost all combinations; CYSDV with CCYV (2/27), CYSDV with CABYV (2/27), CCYV with CABYV (1/27), whereas in one sample CYSDV, CCYV, and CABYV were detected (1/27). BPYV was not detected in any sample tested. PCR products of two CCYV-infected cucumbers were obtained and directly sequenced in both directions using primers targeting portions of the heat shock (226 bp) and the RNA dependent RNA polymerase (RdRp) (709 bp) genes (Orfanidou et al. 2014). BLAST analysis of the obtained sequences of HSP70h (accession nos. LM653107 and LM653108) and RdRp (LM653109 and LM653110) genes revealed 99 and 98% identity, respectively, with the corresponding sequences from an isolate from Lebanon (AB523789). Moreover, transmission experiments were conducted using adult B. tabaci whiteflies feeding on a cucumber leaf singly infected with CCYV. Five groups of 50 whiteflies were given acquisition and inoculation access periods of 48 and 72 h, respectively, and each group was transferred to a healthy cucumber plant. Three weeks post inoculation, yellowing symptoms appear in the lower leaves and virus infection was confirmed in all five test plants by RT-PCR, followed by sequencing, To our knowledge, this is the first report of CCYV infecting cucumber in Saudi Arabia and further surveys are required from more areas in order to determine the spread of the virus in the country and in other cucurbit crops.

Co-infection of two criniviruses and a begomovirus enhances the disease severity in cucumber

In the past two decades, viruses in the genera Crinivirus and Begomovirus, transmitted by whiteflies, have emerged as threatening diseases to cucurbit cultivation. The criniviruses Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV) occur in mixed infection at high rates in cucumber greenhouses in Lebanon. The begomovirus Squash leaf curl virus (SLCV) is also present in the country infecting cucumber but at a lower incidence. The effect of single, dual or triple virus infections on cucumber was studied. Single infection by SLCV did not lead to any symptoms or yield reduction. CYSDV or CCYV infections led to development of characteristic yellowing symptoms. In single infections, CYSDV caused the greatest reductions in height and yield that ranged from 25 to 62 % and 52 to 63 %, respectively, depending on season and variety. CCYV induced less severe reduction in height, 10 to 33 %, and in fruit number, 10 to 12 %. Yellowing symptoms induced by dual infections in any combination were similar to those of singly-infected plants. Triple infections resulted in substantial reductions in plant height and yield as compared to single or dual infections. This is the first report that characterizes a significant increase in disease severity upon co-infection between cucurbit-infecting criniviruses and begomoviruses. The implications of these observations on integrated disease management strategies are discussed.

Spatial and Temporal Analysis of Squash vein yellowing virus Infections in Watermelon.

Squash vein yellowing virus (SqVYV) is a whitefly-transmitted ipomovirus infecting watermelon and other cucurbits that was recently introduced to Florida. Effects on watermelon are devastating, with total vine collapse, often near harvest, and fruit rendered unmarketable by brown, discolored flesh. The epidemiology of SqVYV was studied in a 1-ha field of 'Fiesta' watermelon over six growing seasons (I to VI) to characterize the spatial patterning of disease and temporal rate of disease progress, as well as its association with Cucurbit leaf crumple virus (CuLCrV) and Cucurbit yellow stunting disorder virus (CYSDV), two additional whitefly-transmitted viruses that often occur with SqVYV. The field was scouted at regular intervals for the length of the season for incidence of virus and number of whiteflies. Incidence of SqVYV reached 100% during seasons I, II, and V and 20% during season III. SqVYV did not occur during seasons IV and VI. SqVYV progressed in a characteristic logistic fashion in seasons I, II, and V but less so in season III. The rate of disease progress was similar for the three seasons with high disease incidence, with an average value of 0.18. A positive correlation between the area under the disease progress curve and whitefly-days was found, where both progress curves were calculated as a function of thermal time (degree days, base 0°C). SqVYV displayed significant but variable levels of aggregation, as indicated by its fit to the β-binomial distribution, the binary power law, and ordinary runs analysis. Association analysis indicated that the viruses were largely transmitted independently. Results of this study provide epidemiological information that will be useful in the development of management strategies for SqVYV-induced vine decline, and provide new information for CuLCrV and CYSDV.

First Report of Cucurbit chlorotic yellows virus in Cucumber, Melon, and Watermelon in Greece.

In 2011, an outbreak of a yellowing disease causing chlorosis and Interveinal chlorotic spots on lower leaves was observed in cucumber (Cucumis sativus) and melon (C. melo) plants in two greenhouses on the island of Rhodes, Greece. Similar symptoms were observed in 2012 in open field watermelon (Citrullus lanatus) plants in Rhodes and in November 2013 in a cucumber greenhouse in Tympaki, Crete. Disease incidence ranged from 10 to 40%. The observed symptoms were similar to those caused by whitefly transmitted criniviruses (family Closteroviridae) Cucurbit yellow stunting disorder virus (CYSDV) and Beet pseudo-yellows virus (BPYV), as well as Cucurbit chlorotic yellows virus (CCYV), a recently described crinivirus that infects cucurbits in Japan (4) and by the aphid transmitted polerovirus (family Luteoviridae) Cucurbit aphid-borne yellows virus (CABYV). Dense populations of whiteflies were present in all the affected crops. Leaf samples from cucumber (10 from Rhodes and 10 from Crete), melon (10), and watermelon (10) were collected and tested for the presence of the above viruses. Total RNA was extracted from the samples (2) and detection of BPYV, CYSDV, and CABYV was done as previously described (1,3) whereas detection of CCYV was conducted by herein developed two-step RT-PCR assays. Two new pairs of primers, 'CC-HSP-up' (5'-GAAGAGATGGGTTGGTGTAGATAAA-3')/'CC-HSP-do' (5'-CACACCGATTTCATAAACATCCTTT-3') and 'CC-RdRp-up' (5'-CCTAATATTGGAGCTTATGAGTACA-3')/'CC-RdRp-do' (5'-CATACACTTTAAACACAACCCC-3') were designed based on GenBank deposited sequences of CCYV for the amplification of two regions partially covering the heat shock protein 70 homologue (HSP70h) (226 bp) and the RNA dependent RNA polymerase (RdRp) genes (709 bp). Interestingly, CCYV was detected in all samples tested, while CYSDV was detected in 18 cucumbers (10 from Rhodes and 8 from Crete), 1 melon, and 3 watermelon plants. Neither BPYV nor CABYV were detected. In order to verify the presence of CCYV, the partial HSP70h and RdRp regions of a cucumber isolate from Crete were directly sequenced using the primers 'CC-HSP-up'/'CC-HSP-do' and 'CC-RdRp-up'/'CC-RdRp-do'. BLAST analysis of the obtained sequences (HG939521 and 22) showed 99% and 100% identities with the HSP70h and RdRp of cucumber CCYV isolates from Lebanon, respectively (KC990511 and 22). Also, the partial HSP70h sequence of a watermelon CCYV isolate from Rhodes showed 99% identity with the cucumber isolate from Crete. Whitefly transmission of CCYV was also carried out by using an infected cucumber from Crete as virus source. Four groups of 30 whitefly adults of Bemisia tabaci biotype Q were given an acquisition and inoculation access time of 48 and 72 h, respectively. Each whitefly group was transferred to a healthy cucumber plant (hybrid Galeon). Two weeks post inoculation, the plants, which have already been showing mild interveinal chlorosis, were tested for virus presence by RT-PCR. CCYV was successfully transmitted in three of four inoculated cucumbers, which was further confirmed by sequencing. In Greece, cucurbit yellowing disease has occurred since the 1990s, with CYSDV, BPYV, and CABYV as causal agents. To our knowledge, this is the first report of CCYV infecting cucurbits in Greece; therefore, our finding supports the notion that the virus is spreading in the Mediterranean basin and is an important pathogen in cucurbit crops.

Whitefly‐transmitted RNA viruses that affect intensive vegetable production

AbstractIntensive vegetable production is constantly facing the emergence of new viral diseases. Apart from the intrinsic features of viruses as plant pathogens, the highly dynamic turnover of cultivars and cultural practices, and the global trade of seeds and products characteristic of intensive vegetable production may favour the emergence of new viruses, as well as the expansion of the geographical range of vectors responsible for their dissemination. Indeed, the efficient transmission of viruses plays a major role in the impact and outcome of viral epidemics. Whiteflies (Hemiptera: Aleyrodidae) that belong to the genera Bemisia and Trialeurodes are efficient virus vectors. Whiteflies transmit viruses of at least four genera, one of DNA viruses, the genus Begomovirus, and three of RNA viruses, Crinivirus, Ipomovirus and Torradovirus. Begomoviruses have been the subject of recent reviews. In this article we review the genome structure, epidemiology and control of whitefly‐transmitted RNA viruses that belong to the genera Crinivirus, Ipomovirus and Torradovirus, with an extended discussion on the particular viruses within these genera that are currently causing important outbreaks, such are Cucumber vein yellowing virus (CVYV), Cucurbit yellow stunting disorder virus (CYSDV), Tomato chlorosis virus (ToCV) and Tomato torrado virus (ToTV).

The status of Cucumber vein yellowing virus in Iran

Yellowing symptoms of greenhouse- and open field-grown cucurbit crops are becoming increasingly important in many cucurbit growing regions of the world, and particularly in Iran. A survey was conducted from 2011 to 2012 in eight major cucurbit growing regions in Iran. Yellowing and specifically vein clearing symptoms were observed in many cucumber plants grown in greenhouses and open fields, suggesting the presence of Cucumber vein yellowing virus (CVYV, genus Ipomovirus , family Potyviridae ). The identification of CVYV was carried out with a specific triple-antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) and reverse transcription (RT)-PCR. CVYV was detected in 42% of the collected samples, in all surveyed provinces, except Bushehr. CVYV was also detected in melon and cucumber crops grown in open fields. These results indicate that CVYV is widely distributed on these two cucurbit species in the major cucumber growing areas of Iran. CVYV positive samples were also tested, using DAS-ELISA, for the presence of Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV), two criniviruses reported previously to occur in Iran. Double or triple infections of CCYV and CYSDV occurred in 49 of 166 of the CVYV-infected plants. The CVYV and CCYV combined infections were more prevalent than CVYV and CYSDV combined infections. TAS-ELISA positive samples were used to mechanically inoculate healthy cucumber plants, and mild vein yellowing was observed on the inoculated leaves. Identical symptoms were also observed on whitefly inoculated healthy cucumber plants. The presence of CVYV in mechanically and whitefly inoculated plants was confirmed by TAS-ELISA and RT-PCR. Sequence analysis revealed that the Iranian isolate of CVYV was more closely related to Spanish isolates than to isolates from Jordan. Phylogenetic analysis showed that CVYV isolates can be divided into two phylogenetic groups (I and II). Despite the close vicinity of Jordan to Iran, the Iranian CVYV isolate clustered with Spanish isolates in group I and not with the Jordanian isolates of group II.

Assessing Transmission of Crop Diseases by Insect Vectors in a Landscape Context

Theory indicates that landscape composition affects transmission of vector-borne crop diseases, but few empirical studies have investigated how landscape composition affects plant disease epidemiology. Since 2006, Bemisia tabaci (Gennadius) has vectored the cucurbit yellow stunting disorder virus (CYSDV) to cantaloupe and honeydew melons (Cucumis melo L.) in the southwestern United States and northern Mexico, causing significant reductions in yield of fall melons and increased use of insecticides. Here, we show that a landscape-based approach allowing simultaneous assessment of impacts of local (i.e., planting date) and regional (i.e., landscape composition) factors provides valuable insights on how to reduce crop disease risks. Specifically, we found that planting fall melon fields early in the growing season, eliminating plants germinating from seeds produced by spring melons after harvest, and planting fall melon fields away from cotton and spring melon fields may significantly reduce the incidence of CYSDV infection in fall melons. Because the largest scale of significance of the positive association between abundance of cotton and spring melon fields and CYSDV incidence was 1,750 and 3,000 m, respectively, reducing areas of cotton and spring melon fields within these distances from fall melon fields may decrease CYSDV incidence. Our results indicate that landscape-based studies will be fruitful to alleviate limitations imposed on crop production by vector-borne diseases.

Occurrence and Genome Analysis of Cucurbit chlorotic yellows virus in Iran

In 2011 and 2012, several cucurbit-growing regions of Iran were surveyed and samples with symptoms similar to those induced by Cucurbit chlorotic yellows virus (CCYV) were collected. The pathogen was transmitted to cucumber and melon under greenhouse conditions by whiteflies (Bemisia tabaci). RT-PCR using designed CCYV-specific primer pair (CCYV-F/CCYV-R) resulted in amplification of the predicted size DNA fragment (870 bp) for the coat protein (CP) gene in samples collected from Boushehr, Eyvanakay and Varamin. Nucleotide sequences of the CP of the three Iranian CCYV isolates were compared with five CCYV isolates obtained from GenBank and analysed. Phylogenetically, all CCYV isolates clustered in two groups; Group I is composed of five non-Iranian isolates from China, Lebanon, Japan, Sudan and Taiwan, and the three Iranian isolates formed Group 2. Among Iranian isolates, the Eyvanakay isolate clustered in a distinct clade with the Boushehr and Varamin isolates. A phylogenetic tree based on amino acid identity of CP showed that CCYV was closely related to Lettuce chlorosis virus (LCV), Bean yellow disorder virus (BnYDV) and Cucurbit yellow stunting disorder virus (CYSDV). This is the first report of CCYV in Iran.

First Report of Cucumber vein yellowing virus on Cucumber in Lebanon.

In a 2-year (2008 to 2009) wide-scale survey of viruses infecting cucurbits, a limited number of greenhouse-grown cucumber (Cucumis sativus) plants showed vein-yellowing symptoms. Greenhouses were infested with whiteflies and infection with Cucumber vein yellowing virus (CVYV) was suspected. CVYV is widely distributed in southern Europe in both open field and protected cucurbit crops (2). Total RNA was extracted from seven plants with vein yellowing symptoms using TRI Reagent (Sigma-Aldrich, St Louis, MO). RT-PCR tests using CVYV-specific primers (CV+/CV-) targeting the coat protein of CVYV (2) gave amplicons of the expected size from seven plants. The sequence of one representative isolate, CVYV-LB3 (GenBank Accession No. JF289167), showed 97, 95.6, and 95.2% pairwise nucleotide identity with isolates from Tunisia (EF538680), Israel (AF233429), and Jordan (JF460793), respectively. In 2012, CVYV like symptoms were not observed in greenhouses in the same areas. In early spring 2013, a total of 16 leaf samples with vein-yellowing symptoms were collected from the northern coastal areas (Jbeil, Amshit, Tabarja) and 11 samples showing only yellowing on older leaves from the southern coast (Jiyeh). CVYV was detected in all samples from the northern coast and in four samples from the southern coast. Four isolates from the North and two from the South were sequenced (KC990497 to KC990502) and showed high sequence variation. The pairwise nucleotide and amino acid identities between these isolates ranged from 95.1 to 100% and 98.5 to 100%, respectively. Pairwise nucleotide and amino acid identities of the isolates with CVYV-LB3 showed variable homology between 93.7 to 98.2% and 94.6 to 96.6%, respectively. The inter-population structure of CVYV in Lebanon showed high variability as compared to the homogenous Spanish population (4). For transmission tests, non-viruliferous whiteflies (Bemisia tabaci) were exposed for an 18-h acquisition access period on vein-yellowed leaves followed by a 24-h inoculation access period to healthy cucumber plants (5-leaf stage). In addition, leaves with vein-yellowing symptoms were ground in 0.1 M phosphate buffer (pH 7.0) and sap-inoculated on carborundum-dusted cucumber (cv. Delta) and squash (Cucurbita pepo cv. FarajF1) plants. Vein yellowing symptoms developed 9 to 11 days post-inoculation on all whitefly inoculated plants, while symptoms were delayed till 3 weeks post inoculation on seven out of eight sap-inoculated plants. All symptomatic plants were positive for CVYV by RT-PCR. Furthermore, surveyed plants were also tested for Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV), two criniviruses reported previously in Lebanon, by RT-PCR (1). Double or triple infection of CCYV and CYSDV occurred in 18 out of 20 of the CVYV-infected plants. During the past 5 years, a limited number of cucumber plants showed CVYV symptoms. This indicates that CVYV occurrence is sporadic. However, its occurrence in mixed infection with criniviruses may have damaging economic implications to cucurbit production (3). To our knowledge, this is the first report of CVYV on cucurbits in Lebanon and its occurrence in co-infection with CCYV.

Whitefly-transmitted criniviruses of cucurbits: current status and future prospects.

In the past decade, crinviruses have gained interest due to their rapid widespread and destructive nature for cucurbit cultivation. Several members of the genus Crinivirus are considered emerging viruses. Currently, four criniviruses: Beet pseudo-yellows virus, Cucurbit chlorotic yellows virus, Cucurbit yellow stunting disorder virus and Lettuce infectious yellows virus have been reported to infect field- or greenhouse- grown cucurbits. Apart from their cucurbit hosts, criniviruses infect other cash crops and weeds. Criniviruses are exclusively transmitted by whiteflies. The virion titer and the vector genus or species complex are predominant factors affecting virus transmission. These criniviruses maintain genetic stability with limited intra-species variability. They share similar core genome structure and replication strategies with some variations in the non-core proteins and downstream replication processes. Management of the diseases induced by criniviruses relies on integrated disease management strategies and on resistant varieties, when available. This review will cover their epidemiology, molecular biology, detection and management.

Viruses of cucurbits in Panama.

The main areas of field-grown cucurbit production in Panama were surveyed for the occurrence and distribution of viruses in the growing seasons of 2006 and 2008. Notably, in 2006 only Melon necrotic spot virus (MNSV) was detected, while Papaya ringspot virus (PRSV) was the most frequent in 2008 in terms of number of fields and samples analysed, followed by Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV) and MNSV. Cucumber mosaic virus (CMV), Squash mosaic virus (SqMV), Cucumber green mottle mosaic virus (CGMMV), Tomato spotted wilt virus (TSWV), Cucumber leaf spot virus (CLSV), Cucurbit yellow stunting disorder virus (CYSDV), Cucurbit aphid-borne yellows virus (CABYV), Beet pseudoyellows virus (BPYV), Beet yellows virus (BYV), and Cucumber vein yellowing virus (CVYV) were not detected . Single and double (PRSV+WMV; PRSV+ZYMV; ZYMV+MNSV) infections were detected in 60% and 40% of the samples tested, respectively. The occurrence and distribution of each virus varied according to the region and cucurbit species.

First Report of Cucurbit chlorotic yellows virus Infecting Cucumber, Melon, and Squash in Iran.

Yellowing diseases of field- and greenhouse-grown cucurbits are becoming increasingly important in many cucurbit cultivation areas in Iran. Virus surveys were conducted from 2011 to 2012 in greenhouse-grown cucumber (Cucumis sativus L.) and field-cultivated cucumber, squash (Cucurbita sp.) and melon (Cucumis melo L.) in Tehran, Semnan, Bushehr, Hormozgan, Isfahan, Yazd, and Fars provinces, the major cucurbit-growing areas in Iran. Leaf samples with various symptoms, e.g., chlorosis, interveinal chlorotic spots on lower leaves, bright yellow color or sever yellowing on older leaves, were collected and screened for the presence of the whitefly transmitted criniviruses (family Closteroviridae) Cucurbit chlorotic yellows virus (CCYV) and Cucurbit yellow stunting disorder virus (CYSDV) through double-antibody sandwich (DAS)-ELISA, using CCYV and CYSDV specific antisera (DSMZ, Germany). The ELISA results showed that of 347 cucumber leaf samples originating from cucumber greenhouses, 170 and 65 were positive for CCYV and CYSDV, respectively, and 45 samples were infected with both viruses. In addition, of 147 leaf samples collected from melon, cucumber, and squash grown in open fields, 57 and 53 were infected with CCYV and CYSDV, respectively, and 14 were infected with both viruses. These results indicate that these two viruses are widely distributed on these cucurbit crops in Iran. CCYV was not detected in Bushehr and CYSDV was not detected in Isfahan and Hormozgan provinces. To confirm the presence of CCYV and CYSDV, total RNA was extracted (Sigma Chemical, St. Louis, MO) from 18 samples that reacted positive in DAS-ELISA originating from different surveyed provinces. RT-PCR was carried out using specific primers Crini-s2 (5'-CATTCCTACCTGTTTAGCCA-3') (2) and Crini-as1 (5'-ATCCTTCGCAGTGAAAAACC-3') to amplify a 460-bp fragment of the HSP70 gene and CCYV using specific primers CCYV-HSP-F1 (5'-TGCGTATGTCAATGGTGTTATG-3') and CCYV-HSP-R1 (5'-ATCCTTCGCAGTGAAAAACC-3') to amplify a 462-bp fragment of the HSP70 gene (latter 3 primers from [3]). Expected DNA fragments for CYSDV and CCYV were amplified from 11 (CCYV 7/11, CYSDV 4/11) of 18 samples but not from any of the healthy controls. Further analysis by sequencing three selected PCR products amplified with primers CCYV-HSP-F1/R1 showed complete consensus among the sequences, and in comparison with sequences available at GenBank, the highest identities were obtained to Asian CCYV isolates (94% nt/98% aa identity). The CCYV sequences were deposited in GenBank under accessions KC559449 to KC559451. The identity of the amplified CYSDV DNA could also be confirmed by sequencing of three PCR products. CCYV has first been proven to occur in different countries in East Asia and has recently been reported from Sudan (2) and Lebanon (1), indicating the putative spread of the virus wherever cucurbits are grown and its vector, the whitefly Bemisia tabaci, is present. Large populations of whiteflies were present in all surveyed areas. However, to our knowledge, this is the first report for the occurrence of CCYV in Iran. In conclusion, the presence of CCYV and CYSDV in the major cucurbit growing provinces and the large whitefly population pose a serious threat to cucurbit production in Iran.