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1.
The genetic variation and evolutionary mechanisms shaping Cucumber vein yellowing virus (CVYV) populations were investigated by analysis of nucleotide sequences coding for P1b, P1b/P3 and coat proteins (CP) from isolates collected in different countries. The complete genome sequence of isolate ISM from Israel was also determined and compared to those of isolates Jor from Jordan and ALM32 from Spain. This isolate had overall nucleotide identities of 94·23 and 94·96% with ALM32 and Jor, respectively. Nucleotide variation among isolates was not homogeneously distributed, with the 5′ half of the genome being more variable than the 3′ half. A Bayesian phylogenetic tree of the CP showed that CVYV isolates clustered into two main clades: isolates from the Middle East region (Lebanon, Israel and Jordan) clustered in both clades whereas the isolate from Tunisia clustered in clade I and the European isolates clustered as a homogeneous phylogroup in Clade II. A similar topology was observed for P1b but with incongruences with respect to the CP, suggesting genetic exchange among virus isolates, which were confirmed with recombination algorithms. The low genetic diversity within the European phylogroup with respect to the other isolates, neutralist tests and genetic differentiation analyses suggest that the Middle East region is the cradle of CVYV and that a unique virus introduction event occurred in Europe, where the virus spread rapidly. Taken together, these findings indicate a risk of emergence of virulent CVYV isolates in Europe either through migration from the Middle East or by genetic changes of the European isolates.  相似文献   

2.
Cucurbit yellow stunting disorder virus (CYSDV) has been present in greenhouse-grown cucumber in Spain since 1992. However, in the autumn of 2000 Cucumber vein yellowing virus (CVYV) was introduced, leading to mixed infections of both Bemisia tabaci -transmitted viruses. The temporal and spatial spread of disease symptoms were monitored in experimental plastic-covered greenhouses during six consecutive cucumber plantings from 2000 to 2002. Using linear regression analysis of 46 disease-progress curves, the Gompertz model best described the CYSDV epidemics in 2000, whereas the logistic model best described the development of CYSDV and CVYV epidemics in 2001 and 2002. The fitted models were used to calculate the amount of degree Celsius-days at half-maximum infection in the greenhouses (° D 0·5). After multiple regression analysis, 56% of the variation in ° D 0·5 of CYSDV was related to the numbers of whiteflies infesting the cucumber crops, and was independent of the mean temperatures in the greenhouses. In contrast, 76% of the variation in ° D 0·5 of CVYV was related to both the numbers of vectors present and maximum temperature. Symptom expression in cucumbers mechanically inoculated with CVYV was most prevalent when plants were grown at regimes of at least 28°C day temperature. According to analysis of spread using Taylor's power law, beta-binomial distribution fitting, and the ordinary runs test, the prevalence of CVYV showed significant overdispersion, whereas that of CYSDV did not. The χ2 test of independence and Spearman's rank correlation coefficient were used to measure co-occurrence and covariation, respectively, during the first half of the cultivation period. These results showed that the two diseases were not associated.  相似文献   

3.
Zucchini squash is host to Cucurbit yellow stunting disorder virus (CYSDV), a member of the genus Crinivirus, and Cucumber vein yellowing virus (CVYV), a member of the genus Ipomovirus, both transmitted by the whitefly Bemisia tabaci. Field observations suggest the appearance of new symptoms observed on leaves of zucchini squash crops when both viruses were present. When infected during controlled experiments with CYSDV only, zucchini plants showed no obvious symptoms and the virus titer decreased between 15 and 45 days postinoculation (dpi), after which it was no longer detected. CVYV caused inconspicuous symptoms restricted to vein clearing on some of the apical leaves and the virus accumulated progressively between 15 and 60 dpi. Similar accumulations of virus followed single inoculations with the potyvirus Zucchini yellow mosaic virus (ZYMV) and plants showed severe stunting, leaf deformation, and mosaic yellowing. However, in mixed infections with CYSDV and CVYV, intermediate leaves showed chlorotic mottling which evolved later to rolling, brittleness, and complete yellowing of the leaf lamina, with exception of the veins. No consistent alteration of CVYV accumulation was detected but the amounts of CYSDV increased ≈100-fold and remained detectable at 60 dpi. Such synergistic effects on the titer of the crinivirus and symptom expression were not observed when co-infected with ZYMV.  相似文献   

4.
ABSTRACT The genomes of two Watermelon chlorotic stunt virus (WmCSV) isolates, one from the Sudan and one from Iran, were cloned and sequenced. Sequence relationship with other geminiviruses characterizes WmCSV as a typical Eastern Hemisphere geminivirus with a bipartite genome. The two geographically distant WmCSV isolates from Africa and the Middle East share a very high overall sequence similarity: 98% between their DNA-A and 96% between their DNA-B components, and their respective capsid proteins are identical. A single amino acid change in the capsid protein (N131D) renders WmCSV whitefly nontransmissible. This region of the capsid is also implicated in transmission by Bemisia tabaci of Tomato yellow leaf curl virus.  相似文献   

5.
BACKGROUND: The cotton whitefly, Bemisia tabaci (Gennadius), is a cryptic species complex, and members of the complex have become serious pests in Pakistan because of their feeding and their ability to transmit cotton leaf curl virus (CLCuV). Here, an analysis was made of the identity of B. tabaci collected from cotton and a range of non‐cotton hosts in the cotton‐growing zones in Punjab and Sindh, the main cotton‐producing provinces of Pakistan, using a portion of the mitochondrial cytochrome oxidase 1 gene. The geographic distribution of the different members of the complex was then compared with the incidence of CLCuD. RESULTS: Using the Dinsdale nomenclature, the results revealed three putative species, Asia 1, Asia II 1 and Middle East‐Asia Minor 1. Asia II 1 (also referred to in the literature as biotypes K, P, PCG‐1, PK1, SY and ZHJ2) was only recorded from Punjab cotton plants, whereas Asia 1 (also referred to in the literature as biotypes H, M, NA and PCG‐2) was found in both Sindh and Punjab. Middle East‐Asia Minor 1 (commonly known as biotype B and B2) was found only in Sindh. Moreover, Asia II 1 was associated with high incidences of CLCuD, whereas regions where Middle East‐Asia Minor 1 was present had a lower incidence. Phylogenetic analysis showed that the Middle East‐Asia Minor 1 population in Sindh formed a distinct genetic subgroup within the putative species, suggesting that the Sindh province of Pakistan may form part of its home range. So far, no individuals from the putative species Mediterranean (commonly known as biotypes Q, J and L) have been found in Pakistan. CONCLUSIONS: The capacity to manage pests and disease effectively relies on knowledge of the identity of the agents causing the damage. In the case of CLCuD in Pakistan, this knowledge has been obscured to some extent because of the inconsistent approach to identifying and distinguishing the different B. tabaci associated with CLCuD. The situation has now been clarified, and a strong association between disease incidence and vector identity and abundance has been shown. Given this advance, future research can now focus on factors that influence the capacity of different vector species to transmit the viruses that cause CLCuD, the reason for differences in vector abundance and the lack of geographic overlap between the cryptic vector species. This knowledge will contribute to the development of improved methods with which to manage the disease in Pakistan. Copyright © 2010 Society of Chemical Industry  相似文献   

6.
Symptom expression and levels of the ipomovirus Cucumber vein yellowing virus (CVYV) and the crinivirus Cucurbit yellow stunting disorder virus (CYSDV) were compared in greenhouse cucumbers in single and mixed infections. Results were contrasted with those obtained for plants infected with the potyvirus Zucchini yellow mosaic virus (ZYMV) in single and in mixed infections with either CVYV or CYSDV. Cucumber showed leaf symptoms of each co‐infecting virus, except for the combination of CYSDV with ZYMV, where the typical CYSDV‐like symptoms of interveinal leaf yellowing were inconspicuous or absent. The progression of CVYV as quantified by real‐time RT‐PCR was similar in plants with single infections and in mixed infection with CYSDV between 15 and 60 days post‐inoculation (dpi). However, CYSDV was detected at significantly enhanced levels in plants when co‐infected with CVYV but not when co‐infected with ZYMV. In the latter case, ZYMV levels were reduced when compared with single infections. During mixed infections of ZYMV and CVYV, the titre levels of the ipomovirus were significantly lower when compared with single infections. Cucumber had reduced plant height, internode length, dry weight and fruit yield, positively correlated with the titre levels of CVYV and not of CYSDV during mixed infections. It is concluded that co‐infections with CVYV enhance the titre of CYSDV, which could have epidemiological significance.  相似文献   

7.
Rubio L  Soong J  Kao J  Falk BW 《Phytopathology》1999,89(8):707-711
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8.
Two methods for the detection of Cucumber vein yellowing virus (CVYV) on infected plants were developed, based on the information provided by cDNA clones covering the 3-end of the genome of a Spanish isolate (CVYV-AILM). The sequenced portion of the CVYV-AILM genome showed a 96.6% aminoacid identity with that of a reported sequence of another CVYV isolate from Israel (Lecoq et al., 2000). The first detection method used a RNA specific probe for hybridization with nucleic acids extracted from infected plants. The probe was complementary to a portion of the CVYV genome including the C-terminal part of the NIb and most of the coat protein (CP) coding regions. The second detection method employed polyclonal antisera raised against recombinant viral CP expressed in bacteria. The specific antibodies were used to detect the presence of virus particles in plant extracts. Both procedures resulted in a highly specific detection of CVYV in plants infected with different isolates of the virus. No interference was observed with other cucurbit-infecting viruses. Sensitivities achieved were sufficient for routine diagnosis of the presence of the virus in plants.  相似文献   

9.
The diversity of whitefly‐transmitted begomoviruses in Europe is low, most being exotic, introduced species. The only agriculturally important viruses are two species causing tomato yellow leaf curl. These viruses are believed to have originated in the Middle East but have since spread right across the Mediterranean region. Two ornamentals (Abutilon and Lonicera japonica) were introduced into Europe from the New World and the Far East, respectively, for the striking symptoms induced by the viruses which infect them. The virus infecting honeysuckle (Honeysuckle yellow vein mosaic virus) has been shown to be part of newly identified cluster of begomoviruses which require an additional component, a satellite molecule termed DNA β, to induce symptoms in their host plants. A further begomovirus, Ipomoea yellow vein virus, which infects the weed Ipomoea indica, is present in the Mediterranean region. The precise origin and relationship of this virus to other begomoviruses is unclear.  相似文献   

10.
The Bemisia tabaci (Gennadius) biotype B transmitted host range of Tomato chlorosis virus (ToCV), genus Crinivirus, Family Closteroviridae, and Cucumber vein yellowing virus (CVYV), genus Ipomovirus, Family Potyviridae, was studied. New experimental hosts were identified for each of these viruses. Seventeen species in eight plant families were assessed as potential hosts for ToCV. Infection in asymptomatic Anthriscus cereifolium (chervil) test plants by ToCV was confirmed by using a Real-Time PCR assay designed for ToCV. The presence of readily transmissible, infectious ToCV virions in A. cereifolium was confirmed by re-isolation of the virus via whitefly-transmission from A. cereifolium to Lycopersicon esculentum and A. cereifolium. This is the first report of the experimental transmission of ToCV by B. tabaci to a species within the Umbelliferae. All other hosts assessed for the presence of ToCV were found to be uninfected. Ten species in five families were assessed as potential hosts for CVYV. The CVYV host range identified included some important crops and common weeds, such as L. esculentum, Nicotiana tabacum, A. cereifolium, Datura stramonium, Nicotiana benthamiana, Nicotiana clevlandii and Cucumis sativus. Symptoms were present on D. stramonium, N. benthamiana and C. sativus control plants. The presence of infectious whitefly transmitted CVYV virions was confirmed solely for D. stramonium and N. tabacum, following re-isolation of the virus via B. tabaci transmission from all infected species to C. sativus. This is the␣first report of experimental CVYV transmission by B. tabaci to non-cucurbitaceous crop and weed hosts belonging to the Solanaceae or Umbelliferae.  相似文献   

11.
Agonoscena pistaciae is a serious pest of pistachio in the Middle East and the Eastern Mediterranean. In this paper the presence of the species in Spain and Western Europe is confirmed. It is widespread in the regions of Castilla–La Mancha and Extremadura in Central Spain, where it develops mostly on Pistacia terebinthus, in contrast to the Middle East, where its preferred host is Pistacia vera. In the literature and internet sources, A. pistaciae is often confused with other, morphologically similar species, namely A. succincta and A. targionii. Morphological characters are listed and illustrated for the identification of the species found in the West Mediterranean.  相似文献   

12.
Dicot-infecting mastreviruses affect chickpea (Cicer arietinum) plants by causing extreme stunting of the plant and leaf lamina reduction. Chickpea stunt disease (CSD) is presently known to occur in Africa, the Middle East and Asia. Although the disease was first recorded in India, little was known about the pathogen causing the disease. In this study we determined the complete nucleotide sequence of the mastrevirus associated with CSD in the region of Delhi. The genomic component of the virus was cloned using a rolling circle amplification (RCA) method. The virus isolate was found to show 99% sequence identity with the Chickpea chlorotic dwarf Pakistan virus. The complete tandem dimeric construct of the virus was found to be highly infectious to chickpea, and induced severe stunting of the plant, leaf smalling, drying, and the eventual death of the plant. Phylogenetic analysis of all the chickpea-infecting mastreviruses helped to distinguish the current differences between viruses originating from Africa, the Middle East, Asia and Australia.  相似文献   

13.
E. Bouma 《EPPO Bulletin》2005,35(2):233-238
Data on the efficacy and crop safety of plant protection products can be used for registration purposes in other countries, provided crop growth conditions are comparable. This article identifies the main conditions which are relevant in this respect, with particular emphasis on climatic conditions. Comparison of several systems of agro‐climatic classification developed for the EPPO region, particularly the climate diagrams of Walter & Lieth, the climate classification system of Köppen & Geiger, the agro‐climatic areas of Thran & Broekhuizen and natural vegetation maps, has led to a division of the EPPO region (Europe, Mediterranean area, Middle East) into four agro‐climatic zones (Mediterranean, Maritime, North‐east, Central) within which conditions can be considered comparable.  相似文献   

14.
Cucurbit yellow stunting disorder crinivirus infects cucurbit crops in the Middle East and the Mediterranean area (Egypt, Morocco, Spain, Portugal, South of France since 2001). Transmitted by Bemisia tabaci in a semipersistent manner, this virus provokes interveinal yellowing on older leaves of cucurbits, and is reported to cause significant economic losses in cucumber crops in Lebanon. Since it is very difficult to purify CYSDV, the main technique used for detection is RT-PCR, which is not appropriate for routine tests. Therefore, the coat protein gene of a French isolate of CYSDV was amplified by RT-PCR, cloned into bacterial expression vector pET16b allowing fusion of the protein with a N-terminal 10xHis-tag for easier purification, and transformed into Escherichia coli , strain BL21(DE3). The recombinant coat protein was produced at a high level, purified from cell lysates on a Ni-NTA resin column, and used as an antigen to immunize a rabbit (three intradermal then six subcutaneous injections every 3 or 4 weeks). The resulting antiserum can be successfully used in DAS-ELISA tests.  相似文献   

15.
Tomato spotted wilt virus was recorded for the first time in Jordan on tomato plants. Severe disease symptoms were observed in different tomato farms in the Jordan Valley. Using a specific primer pair a fragment of the capsid protein gene of the virus has been amplified by RT-PCR and IC-RT-PCR. The amplified PCR product was cloned and sequenced. Sequence analysis revealed that the Jordanian isolate of TSWV shared high nucleotide similarities with other isolates from different countries. The sequence of the capsid protein gene was deposited in GenBank under the accession number AY646682 . The response of different tomato breeding lines and hybrids, previously developed for resistance against Tomato yellow leaf curl virus (TYLCV) were tested for their reaction to TSWV infection. All tested lines and hybrids were susceptible to TSWV infection. This has been confirmed at the molecular level by using the SCAR 421 marker linked to the TSWV resistance gene Sw-5 .  相似文献   

16.
Geminivirus defective interfering DNAs arise spontaneously in mechanically inoculated test plants, and have previously been found with DNA-B of the bipartite cassava mosaic geminiviruses, but not DNA-A. Reported here for the first time is the cloning and characterization of a naturally occurring truncated form of cassava mosaic geminivirus DNA-A, which at 1525 nt is around half the expected full size. Sequence analysis has shown it to be a defective (df) form of East African cassava mosaic virus (EACMV) DNA-A that has retained its cis elements essential for replication by the helper virus, and it has been termed df DNA-A 15. Phylogenetic comparisons placed the df DNA-A 15 molecule close to mild and severe isolates of EACMV-UG2. Biolistic inoculation of Nicotiana benthamiana with infectious df DNA-A 15 clone and East African cassava mosaic Cameroon virus (EACMCV) resulted in symptom amelioration as compared with EACMCV singly inoculated plants, and there was an accumulation of df DNA-A 15 in systemically infected leaves. In addition, the level of EACMV DNA-B accumulation was reduced in the coinoculated plants compared with those inoculated with EACMCV alone. PCR and sequence analysis confirmed the helper virus as EACMV.  相似文献   

17.
ABSTRACT In the late 1990s, commercial garlic fields in California (CA) were devastated by an outbreak of rust caused by Puccinia allii. We compared collections of the pathogen from garlic (Allium sativum) and chives (A. schoenoprasum) in central CA and Oregon (OR) to collections from garlic and leek (A. porrum and A. ampeloprasum) in the Middle East. Teliospores from the CA and OR collections were smaller in length, width, and projected cross-sectional area compared with collections from the Middle East. CA and OR collections had a shortened life cycle, in which pycnia and aecia were not formed. Germinating teliospores produced a two-celled promycelium, resulting in two basidiospores, each initially with two nuclei, indicating that this rust was homothallic. In addition, the morphology of the substomatal vesicles was different between the CA-OR (fusiform) and the Middle Eastern (bulbous) collections. DNA sequence analysis of the nuclear ribosomal internal transcribed spacer region showed that the CA and OR rust collections formed a well-supported cluster distinct from the Middle Eastern and European samples. These results suggest that the rust on garlic and chives in CA and OR is a different species than the rust fungus on garlic and leek in the Middle East.  相似文献   

18.
Non-crop plants such as grasses and volunteer plants are an inseparable part of the flora of crop fields and can influence virus incidence in crop plants. The presence of grasses as virus reservoirs can lead to a higher probability of virus incidence in crop plants. However, the role of reservoirs as an inoculum source in agricultural fields has not been well studied for many viral diseases of crops. Grasses have been found to constitute potential reservoirs for cereal-infecting viruses in different parts of the world. This study revealed that cereal-infecting viruses such as wheat dwarf virus (WDV), barley yellow dwarf viruses (BYDVs), and cereal yellow dwarf virus-RPV (CYDV-RPV) can be found among ryegrass growing in or around winter wheat fields. Phylogenetic analysis showed that a WDV isolate from ryegrass was a typical WDV-E isolate that infects wheat. Similarly, a ryegrass isolate of barley yellow dwarf virus-PAV (BYDV-PAV) grouped in a clade together with other BYDV-PAV isolates. Inoculation experiments under greenhouse conditions confirmed that annual ryegrass of various genotypes can be infected with WDV to a very low titre. Moreover, leafhoppers were able to acquire WDV from infected ryegrass plants, despite the low titre, and transmit the virus to wheat, resulting in symptoms. Information from the grass reservoir may contribute to improving strategies for controlling plant virus outbreaks in the field. Knowledge of the likely levels of virus in potential reservoir plants can be used to inform decisions on insect vector control strategies and may help to prevent virus disease outbreaks in the future.  相似文献   

19.
ABSTRACT Epidemics of tomato yellow leaf curl disease (TYLCD) in the Dominican Republic in the early to mid-1990s resulted in catastrophic losses to processing tomato production. As part of an integrated management approach to TYLCD, the complete nucleotide sequence of a full-length infectious clone of an isolate of Tomato yellow leaf curl virus (TYLCV) from the Dominican Republic (TYLCV-[DO]) was determined. The TYLCV-[DO] genome was nearly identical in sequence (>97%) and genome organization to TYLCV isolates from Israel and Cuba. This established that TYLCV-[DO] is a bonafide TYLCV isolate (rather than a recombinant virus, such as isolates from Israel [Mild], Portugal, Japan, and Iran), and provided further evidence for the introduction of the virus from the eastern Mediterranean. A reduction in the incidence of TYLCV in the northern and southern processing tomato production areas of the Dominican Republic has been associated with the implementation of a mandatory 3-month whitefly host-free period (including tomato, common bean, cucurbits, eggplant, and pepper). Monitoring TYLCV levels in whiteflies, by polymerase chain reaction with TYLCV-specific primers, established that the incidence of TYLCV decreased markedly during the host-free period, and then gradually increased during the tomato-growing season. In contrast, TYLCV persisted in whiteflies and tomato plants in an area in which the host-free period was not implemented. Surveys for TYLCV reservoir hosts, conducted to identify where TYLCV persists during the host-free period, revealed symptomless infections in a number of weed species. The implications of these findings for TYLCV management in the Dominican Republic are discussed.  相似文献   

20.
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