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1.
Cucumber mosaic virus is one of the most prevalent viruses in Tunisian pepper crops, where it has been detected in 68% of plants developing mosaic symptoms, making it essential to characterize the molecular and biological properties of local CMV populations. Two hundred and seventy‐eight isolates collected in the late 1990s, 2006 and 2008–2010 were characterized genetically. Isolates belonging to the three phylogenetic subgroups of CMV (IA, IB and II) were detected, but surprisingly, 90% of the isolates were reassortants between subgroups IA and IB, with two predominant haplotypes, IB‐IA‐IA and IB‐IA‐IB (nomenclature according to the subgrouping of the three genomic RNAs). The IB‐IA‐IA haplotype was present in all regions surveyed, while IB‐IA‐IB was observed only in northern Tunisia. This situation was unexpected, because CMV reassortants were previously thought to be counterselected in nature, and this raises the questions of the origin of IB strains in Tunisia and of the widespread distribution of these two reassortant types. Phylogenetic studies revealed low diversity within haplotypes, whatever the locality or the year of sampling. However, analysis of haplotype frequencies revealed a high genetic differentiation between CMV populations, which was better explained by the localities of sampling than by years. Geographic distances affected the differentiation of CMV populations, mainly between north and central Tunisia. When tested against a polygenic resistance to CMV movement in pepper, 55 of 57 isolates tested were able to break the resistance, indicating that this resistance would not be useful for controlling CMV in Tunisian pepper fields.  相似文献   

2.
Two important sources of Capsicum annuum (bell pepper) resistance were evaluated for their response to inoculation with two isolates of Tobacco etch virus strain NW (TEV‐NW, genus Potyvirus). The resistant cultivars were CA4 and Dempsey, which contain the pvr1 and pvr12 resistance genes, respectively. TEV‐NW was maintained by mechanical passage in the susceptible pepper cultivar Early Calwonder and Nicotiana tabacum cv. Kentucky 14. In initial experiments, the TEV‐NW isolate maintained in Early Calwonder infected two of seven CA4 plants; however, none of the CA4 plants inoculated with the TEV‐NW isolate maintained in Kentucky 14 were infected. The infected CA4 plants had low virus titres in non‐inoculated leaves and did not develop visible symptoms. When the infected CA4 plants were used as inoculum of additional CA4 plants, all newly inoculated plants became infected, developed systemic symptoms and accumulated virus in non‐inoculated leaves more quickly than the originally infected CA4 plants. This new NW isolate, referred to as NW‐CA4, was shown to overcome the resistances expressed by both CA4 (pvr1) and Dempsey (pvr12). The potyviral VPg is believed to be the determinant for pvr1 and pvr12 resistance genes, both of which are eIF4E‐encoding genes. The VPg amino acid sequence for NW‐CA4 was determined and compared with that of NW isolates and different TEV strains. No amino acid variation was identified that explained the infectivity of NW‐CA4 in CA4 and Dempsey plants.  相似文献   

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4.
Widely used resistant peppers (Capsicum spp.) bearing the Tsw locus triggered the rapid emergence of resistance‐breaking (RB) isolates of Tomato spotted wilt virus (TSWV) around the world. However, although TSWV‐induced diseases have rapidly increased in Yunnan, southwest China, in recent years, no information is available about the diversity of TSWV isolates in this region. In this study, the occurrence of natural TSWV RB variants among isolates collected in Yunnan is reported. Initially, a TSWV isolate from asparagus lettuce (TSWV‐LE) was collected in Yunnan in 2012. Surprisingly, this isolate of TSWV induced systemic necrosis on pepper carrying the Tsw resistance gene. Novel TSWV isolates, collected in 2015, included a tomato isolate (TSWV‐YN18) and a tobacco isolate (TSWV‐YN53) that also overcame Tsw‐mediated resistance. TSWV‐YN18 induced systemic ringspots, whereas TSWV‐YN53 caused systemic chlorotic mottling. Variations in the TSWV nonstructural (NSs) protein are the key determinants associated with Tsw resistance‐breaking isolates. It was found that TSWV‐LE NSs retained the hypersensitive response (HR) induction, whereas TSWV‐YN18 and TSWV‐YN53 NSs were unable to induce HR. However, the NSs of all three RB isolates suppressed RNA silencing. Sequence analysis of the NSs revealed that RB isolates of Yunnan have no amino acid mutation sites common to other previously reported RB isolates. However, two amino acids (F74 and K272) on TSWV‐LE NSs make it distinct from TSWV‐YN18 and TSWV‐YN53. The occurrence of different RB isolates and the failure of Tsw‐mediated resistance control pose serious threats to domestic pepper crops in southwest China.  相似文献   

5.
Recombination has played an important role in evolution and genetic diversity of Sugarcane yellow leaf virus (SCYLV) isolates sequenced to date. This study found that three newly sequenced SCYLV sorghum isolates from the USA underwent intraspecies recombination. No statistical significance on probable progeny–parent relationships involving SCYLV sorghum isolates were found in possible interspecies recombination with 18 members of the Luteoviridae family. Sorghum isolates deposited in the GenBank database under accession numbers KT960995, KT960996 and KT960997 were phylogenetically closely related to SCYLV genotypes IND, CUB and CHN1, all members of phylogroup II. Networked relationships among the sorghum isolates showed that numerous incompatibilities occurred in the sequences. These conflicting signals were probably due to recombination, especially in KT960997, which was heavily impacted by recombination. The KT960997 accession was positioned on a distinct branch compared to other members of phylogroup II, suggesting that it has probably emerged as a new genotype. Future studies on molecular evolution may reveal further insights into the adaptation capacity of these SCYLV lineages to new environments.  相似文献   

6.
Wild and cultivated Fragaria chiloensis ssp. chiloensis (Fcc) plants were collected at different locations in southern Chile in order to determine the current viral status of this native strawberry. The following aphidborne viruses (ABVs): Strawberry mild yellow edge virus (SMYEV), Strawberry mottle virus (SMoV), Strawberry crinkle virus (SCV) and Strawberry vein banding virus (SVBV), were found in wild and cultivated Fcc plants, but severe symptoms were not associated with viral infection. Furthermore, partial gene sequences of these ABV isolates were determined and displayed a high degree of conservation with virus isolates reported previously. In addition, partial gene sequences of SCV and SVBV from southernmost South American populations of Fcc are described for the first time. High‐throughput parallel sequencing (Illumina) of double‐stranded RNA was used to provide viral profiles of Fcc from different locations. Although strong evidence of novel viruses affecting Fcc was not found, it was confirmed that ABVs are the most frequent viruses affecting this subspecies. The information provided will help in the development of high‐quality molecular tools for virus detection and control in Fcc.  相似文献   

7.
为明确我国黄瓜花叶病毒株系分化及系统进化基本情况,从湖南、新疆、青海和海南4省区采集1 367个样品对其进行酶联免疫和RT-PCR检测,并对分离获得的15个黄瓜花叶病毒(Cucumber mosaic virus,CMV)纯化分离物CP、MP、2b核苷酸序列进行相似性和进化树分析及生物学性状比较。结果表明,辣椒、龙葵和黄瓜的CMV阳性检出率较高,分别为54.13%、29.19%和18.46%。进化树分析显示CMV-Q5与CMV亚组II的亲缘性较高;CMV-N7为新发现的重组株系,其CP、2b基因属于CMV亚组IB,MP基因却属于CMV亚组II;其余13个分离物均属于CMV亚组IB。CMV-N7和CMV-Q5在系统寄主心叶烟和枯斑寄主苋色藜上引发的症状相似,但比对照株系CMV-P3613(IB)的发病时间要晚1~2 d,系统花叶较温和,枯斑较小。表明在以上4省区常见农作物上广泛流行的CMV存在分子变异。  相似文献   

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9.
Alstroemeria plants were surveyed for viruses in Japan from 2002 to 2004. Seventy-two Alstroemeria plants were collected from Aichi, Nagano, and Hokkaido prefectures and 54.2% were infected with some species of virus. The predominant virus was Alstroemeria mosaic virus, followed by Tomato spotted wilt virus, Youcai mosaic virus (YoMV), Cucumber mosaic virus (CMV), Alstroemeria virus X and Broad bean wilt virus-2 (BBWV-2). On the basis of nucleotide sequence of the coat protein genes, all four CMV isolates belong to subgroup IA. CMV isolates induced mosaic and/or necrosis on Alstroemeria. YoMV and BBWV-2 were newly identified by traits such as host range, particle morphology, and nucleotide sequence as viruses infecting Alstroemeria. A BBWV-2 isolate also induced mosaic symptoms on Alstroemeria seedlings.  相似文献   

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12.
Four Cucumber mosaic virus (CMV) (CMV-HM 1–4) and nine Tomato mosaic virus (ToMV) (ToMV AH 1–9) isolates detected in tomato samples collected from different governorates in Egypt during 2014, were here characterized. According to the coat protein gene sequence and to the complete nucleotide sequence of total genomic RNA1, RNA2 and RNA3 of CMV-HM3 the new Egyptian isolates are related to members of the CMV subgroup IB. The nine ToMV Egyptian isolates were characterized by sequence analysis of the coat protein and the movement protein genes. All isolates were grouped within the same branch and showed high relatedness to all considered isolates (98–99%). Complete nucleotide sequence of total genomic RNA of ToMV AH4 isolate was obtained and its comparison showed a closer degree of relatedness to isolate 99–1 from the USA (99%). To our knowledge, this is the first report of CMV isolates from subgroup IB in Egypt and the first full length sequencing of an ToMV Egyptian isolate.  相似文献   

13.
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14.
In surveys conducted in 2011 and 2012 to identify the viruses causing diseases on pepper and tomato in the department of Alibori in northern Benin, 451 samples of pepper and tomato were analyzed by ELISA using 11 specific antibodies. The highest virus incidence among the surveyed districts was recorded on pepper in Malanville (56.18%), followed by Karimama (39.32%). The most frequently found viruses were Pepper veinal mottle virus (PVMV), Cucumber mosaic virus (CMV), and Potato virus Y-necrotic (PVY-n), accounting respectively for 22.39%, 21.73% and 15.96% of the collected samples. Tomato yellow leaf curl virus (TYLCV) was detected in only 2.43% of the samples, whereas Alfalfa mosaic virus (AMV), Chilli veinal mottle virus (ChiVMV), Tomato mosaic virus (ToMV) and Tomato spotted wilt virus (TSWV) were not detected in any of the samples tested. Double and triple infections involving different virus combinations were found, respectively, in 14.86% and 4% of the samples. Five plant species (Euphorbia hirta Linnaeus, Moringa oleifera Lam, Leucas martinicencis (Jacquin) R. Brown, Combretum micranthum G. Don, Abelmoschus esculentus L. Moench.) out of 30 samples belonging to 13 botanical families, collected within or nearby tomato and pepper fields, were found infected with PVMV, PVY-n, and CMV. Control measures to reduce the impact of viruses on pepper and tomato production are discussed. This is the first report of viruses infecting pepper and tomato in Benin.  相似文献   

15.
Cucumber mosaic virus (CMV) has resulted in much damage to Danshen (Salvia miltiorrhiza Bunge) crops in China. A 5-year survey was conducted in Hebei, Shandong, Sichuan, Shanxi, Henan and Gansu Provinces, all major Danshen-growing areas. A total of 156 Danshen plant samples with CMV symptoms were collected and tested for the presence of CMV by a double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) using polyclonal antibodies against CMV and a positive control, according to the supplier’s instructions (Agdia). They were confirmed to be CMV by amplification of complete coat protein gene and analysis of the gene sequence. The results showed that 122 samples were infected by CMV and all of these CMV isolates belonged to subgroup IB. http://www.phytoparasitica.org posting May 19, 2008. Joint first authors.  相似文献   

16.
Tomato yellow leaf curl disease is one of the most devastating viral diseases affecting tomato crops worldwide. This disease is caused by several begomoviruses (genus Begomovirus, family Geminiviridae), such as Tomato yellow leaf curl virus (TYLCV), that are transmitted in nature by the whitefly vector Bemisia tabaci. An efficient control of this vector‐transmitted disease requires a thorough knowledge of the plant–virus–vector triple interaction. The possibility of using Arabidopsis thaliana as an experimental host would provide the opportunity to use a wide variety of genetic resources and tools to understand interactions that are not feasible in agronomically important hosts. In this study, it is demonstrated that isolates of two strains (Israel, IL and Mild, Mld) of TYLCV can replicate and systemically infect A. thaliana ecotype Columbia plants either by Agrobacterium tumefaciens‐mediated inoculation or through the natural vector Bemisia tabaci. The virus can also be acquired from A. thaliana‐infected plants by B. tabaci and transmitted to either A. thaliana or tomato plants. Therefore, A. thaliana is a suitable host for TYLCV–insect vector–plant host interaction studies. Interestingly, an isolate of the Spain (ES) strain of a related begomovirus, Tomato yellow leaf curl Sardinia virus (TYLCSV‐ES), is unable to infect this ecotype of A. thaliana efficiently. Using infectious chimeric viral clones between TYLCV‐Mld and TYLCSV‐ES, candidate viral factors involved in an efficient infection of A. thaliana were identified.  相似文献   

17.
The development of plant diseases is associated with biophysical and biochemical changes in host plants. Various sensor methods have been used and assessed as alternative diagnostic tools under greenhouse conditions. Changes in photosynthetic activity, spectral reflectance and transpiration rate of diseased leaves, inoculated with Cucumber mosaic virus (CMV), Cucumber green mottle mosaic virus (CGMMV), and the powdery mildew fungus Sphaerotheca fuliginea were assessed by the use of non‐invasive sensors during disease development. Spatiotemporal changes in leaf temperature related to transpiration were visualized by digital infrared thermography. The maximum temperature difference within a leaf was an appropriate parameter to differentiate between healthy and diseased plants. The photosynthetic activity of healthy and diseased cucumber plants varied as measured by chlorophyll fluorescence and compared to the actual chlorophyll content. Hyperspectral imaging data were analysed using spectral vegetation indices. The results from this study confirm that each pathogen has a characteristic influence on the physiology and vitality of cucumber plants, which can be measured by a combination of non‐invasive sensors. Whereas thermography and chlorophyll fluorescence are unspecific indicators for plant diseases, hyperspectral imaging offers the potential for an identification of plant diseases. In a sensor data fusion approach, an early detection of each pathogen was possible by discriminant analysis. Although it still needs to be validated under real conditions, the combination of information from different sensors seems to be a promising tool.  相似文献   

18.
Cherry leaf roll virus (CLRV) isolates from Malus domestica, Ribes rubrum, Rubus idaeus, Rumex obtusifolius and Vaccinium darrowii were characterized based on nucleotide sequences of a 371 bp fragment of the 3′ untranslated region (UTR) of their genomic RNAs, symptoms in the herbaceous hosts, Chenopodium amaranticolor, Chenopodium quinoa, Nicotiana benthamiana, Nicotiana occidentalis and Nicotiana tabacum, and seed transmission in N. occidentalis. The different isolates induced a range of localized and systemic disease symptoms, of varying severity, in the herbaceous hosts. The isolates from M. domestica, R. rubrum, R. obtusifolius and V. darrowii all showed greater than 80% seed transmission in N. occidentalis, but no seed transmission was observed for the R. idaeus isolate. Based on symptoms and seed transmission, the isolates appear to be biologically distinct strains of CLRV. Phylogenetic analysis of the nucleotide sequences from the 3′ UTR, commonly used to detect CLRV, showed that four isolates from M. domestica, R. rubrum, R. idaeus and V. darrowii were almost identical but an isolate from R. obtusifolius exhibited a pairwise nucleotide difference of up to 5·4% when compared to these isolates. There was no obvious correlation between sequence differences and symptomatology.  相似文献   

19.
Cannas are tropical and subtropical flowering perennial plants. The genus contains many species but most commercially grown cultivars are interspecific hybrids selected for their attractive foliage and flowers. Canna production is so lucrative that there are farmers and nurseries dedicated solely to its production. The specific issue that the canna industry faces is virus diseases. In this study, rhizomes of 24 canna cultivars were gathered and diagnostics conducted to detect Bean yellow mosaic virus (BYMV, Potyvirus), Canna yellow mottle virus (CaYMV, Badnavirus), Canna yellow streak virus (CaYSV, Potyvirus), Cucumber mosaic virus (CMV, Cucumovirus) and Tomato aspermy virus (TAV, Cucumovirus). Visual assessment of disease symptoms and diagnostic tests were carried out to identify the prevalent diseases and describe the symptoms that are associated with virus infection. BYMV, CaYMV and CaYSV caused severe mosaic and necrosis either in the leaf lamina or veins of infected leaves. Potyvirus infection suppressed red colouration in the foliage of some varieties. CaYMV and CaYSV often appeared in the same plant, suggesting they might represent a viral complex. CMV and TAV were rarely seen in these populations. Interestingly, CaYMV but not CaYSV could be mechanically inoculated to Phaseolus vulgaris plants.  相似文献   

20.
Little is known about the natural occurrence and genetic variability of nepovirus large satellite RNA (satRNA). This study screened 71 Grapevine fanleaf virus (GFLV) isolates mainly from Slovenia, but also from other countries in Europe and the USA, for the presence of satRNA, using a newly developed RT‐PCR assay. GFLV satRNA (satGFLV) was detected in 72% of naturally GFLV‐infected grapevines analysed, which is the highest frequency of occurrence of satGFLV reported to date. From 39 naturally GFLV‐infected grapevines, 122 satGFLV clones were sequenced and compared to publicly available sequences of satGFLVs and the closely related satRNAs from Arabis mosaic virus (satArMVs). Phylogenetic analyses of these satRNAs revealed that their evolution was driven by substitutions, insertions, deletions, recombinations and reassortments between closely related helper viruses. Phylogenetic relationships of the satGFLVs and satArMVs show their separate and subsequent common evolution. Furthermore, the satGFLVs varied in size and showed higher variability at the amino acid level than at the nucleotide level, just as the 2AHP gene of their helper virus. This study shows that satGFLVs are also similar to their helper virus with respect to their quasispecies nature and their transmission route through anthropogenic exchange of propagation material.  相似文献   

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