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1.
Euphorbia mosaic virus (EuMV), a tentative species within the genus Begomovirus, was isolated from Euphorbia heterophylla plants growing in the Yucatan Peninsula, Mexico. The complete bipartite genome was cloned from total DNA extracts and the nucleotide (nt) sequence was determined. The DNA-A sequence of the EuMV-Yucatan Peninsula (EuMV-YP) isolate shared 95% nt identity with the partially characterized type EuMV isolate from Puerto Rico. The EuMV-YP genome organization was like that of other New World, bipartite begomoviruses. The DNA-A component was 2613 nt in size, while the DNA-B component was 2602 nt long. The 165-nt common region (CR) sequence for the DNA-A and DNA-B components shared a lower than expected nt identity of 86%. The organization and iterons of the putative AC1 binding site of EuMV-YP were similar to those of begomoviruses in the Squash leaf curl virus (SLCV) clade. Characteristic disease symptoms were reproduced in E. heterophylla plants inoculated at the seedling stage using the cloned viral DNA-A and DNA-B components, confirming disease aetiology. Results of an experimental host-range study for EuMV-YP indicated that it infected at least five species in three plant families, including the Euphorbiaceae ( E. heterophylla ), Solanaceae ( Datura stramonium , pepper, tomato) and Fabaceae (bean). Phylogenetic analysis of the DNA-A and DNA-B components indicated that EuMV-YP is a New World begomovirus and that it is a new member of the SLCV clade.  相似文献   

2.
Begomoviruses were detected in Nicaraguan fields of tomato ( Lycopersicon esculentum ) and adjacently growing plants of pepper ( Capsicum annuum ), chilli pepper ( C . baccatum ), cushaw ( Cucurbita argyrosperma ) and Mexican fireplant ( Euphorbia heterophylla ) using polymerase chain reaction (PCR) and universal begomovirus primers. All tomato and Mexican fireplant plants showing symptoms were infected with begomoviruses, while only 30–46% of the pepper, chilli pepper and cushaw plants showing symptoms tested virus-positive. No begomoviruses were found in potato. The virus species were provisionally identified by sequencing 533 bp of the viral coat protein gene ( AV1 ). Tomato severe leaf curl virus (ToSLCV), Tomato leaf curl Sinaloa virus (ToLCSinV) and Pepper golden mosaic virus (PepGMV) were found to infect both tomato and pepper. A new provisional species designated Tomato leaf curl Las Playitas virus (ToLCLPV) was detected in a tomato plant. Squash yellow mottle virus (SYMoV) and PepGMV were found in cucurbits, the latter for the first time in this host. Euphorbia mosaic virus (EuMV) was detected in Mexican fireplant. Sequencing of a larger number of PCR-amplified clones from selected plants revealed intraspecific viral sequence variability, and also multiple begomovirus infections which could represent up to three species in a single tomato or cushaw plant. Phylogenetic grouping of virus sequences did not correlate with the host of origin.  相似文献   

3.
Genomic characterization using nonradioactive probes, polymerase chain reaction with degenerate primers for whitefly transmitted geminiviruses and nucleotide sequencing were used to describe a new bipartite geminivirus, associated with dwarfing and leaf curling of tomatoes and peppers in Jamaica. Partial DNA-A and DNA-B clones were obtained. DNA sequence analysis showed that tomato and pepper samples have a similar geminivirus associated with them. Nucleotide sequence identity > 92% between the common regions of DNA-A and DNA-B confirmed the bipartite nature of the Jamaican geminivirus isolates. Nucleotide sequence comparisons of DNA-A and DNA-B with those of geminiviruses representing the major phylogenetic groups of Western Hemisphere geminiviruses showed the greatest similarity to potato yellow mosaic virus and members of the Abutilon mosaic virus cluster of geminiviruses. This new virus is given the name tomato dwarf leaf curl virus (TDLCV) because of the dwarfing and leaf curling symptoms associated with infected tomato plants. Polymerase chain reaction and Southern hybridization showed mixed infections of TDLCV with tomato yellow leaf curl virus from Israel in 16% of the field samples of tomatoes and peppers.  相似文献   

4.
In West and Central Africa, as in many regions of the world, vegetables are severely affected by geminivirus diseases. In Burkina Faso, observation of various virus-like symptoms, especially on tomato, suggests the involvement of several geminiviruses and underlines the pressing need for additional information on their diversity, distribution, prevalence and host plant reservoirs. Large-scale surveys conducted in Burkina Faso confirmed the presence of tomato (yellow) leaf curl diseases (ToLCD-TYLCD) and geminiviruses in all localities with mean prevalences of 25% and 45%, respectively. Five geminiviruses including four begomoviruses (pepper yellow vein Mali virus (PepYVMLV), tomato leaf curl Burkina Faso virus, tomato leaf curl Mali virus and tomato leaf curl Ghana virus) and a dicot-infecting mastrevirus (chickpea chlorotic dwarf virus) were characterized on tomato. In addition, PepYVMLV and cotton leaf curl Gezira virus (CLCuGeV) were characterized on pepper and okra, respectively, in combination or not with alphasatellites and betasatellites for CLCuGeV. The most severe, prevalent and widely distributed virus on vegetables was PepYVMLV, which was characterized for the first time in combination with a genetically divergent DNA-B component that may constitute a key factor of PepYVMLV pathogenicity. Of the eight weeds identified as potential reservoir hosts of begomoviruses, four host PepYVMLV. The results confirm the importance of geminivirus diseases on vegetable crops in Burkina Faso and highlight the complex association of geminiviruses and satellites. The detection of begomoviruses in weeds growing close to crops points to the increasing necessity to consider reservoir plants and virus communities in the control of virus diseases.  相似文献   

5.
<正>番茄黄化曲叶病毒(Tomato yellow leaf curl virus,TYLCV)在世界范围内可危害多种作物,造成植株矮化、叶片皱缩变形、局部黄化等症状。该病毒自1964年首次报道以来已蔓延至世界多地。在我国2006年上海首次报道该病毒[1],随后江苏、山东、安徽、北京、河北、天津等地相继报道,危害严重。TYLCV为双生病毒科(Geminiviridae)菜豆金色花叶病毒属(Begomovirus)成员,基因组为单组  相似文献   

6.
ABSTRACT Three isolates of the bipartite begomovirus Pepper golden mosaic virus (PepGMV) were characterized for genomic and biological properties. The complete nucleotide sequences of the DNA-A and DNA-B components were determined from infectious clones of PepGMV-Serrano (PepGMV-Ser), PepGMV-Mosaic (PepGMV-Mo), and PepGMV-Distortion (PepGMV-D). Nucleotide sequence identity among PepGMV components ranged from 91 to 96% for DNA-A and from 84 to 99% for DNA-B, with each PepGMV component most closely related to the corresponding component of Cabbage leaf curl virus (CaLCV). However, phylogenetic relationships among begomovirus components were incongruent because DNA-A of PepGMV and CaLCV share an inferred evolutionary history distinct from that of DNA-B. The cloned components of PepGMV-Ser, -Mo, and -D were infectious by biolistic inoculation to pepper but differed in symptom expression: PepGMV-Ser exhibited a bright golden mosaic, PepGMV-Mo produced a yellow-green mosaic, and PepGMV-D caused only a mild mosaic and foliar distortion followed by a "recovery" phenotype in which leaves developing after initial symptom expression appeared normal. Differences in symptoms also were observed on tomato, tobacco, and Datura stramonium. Progeny virus derived from clones of PepGMV-Ser and -Mo were transmitted from pepper to pepper by the B biotype of Bemisia tabaci; progeny virus derived from PepGMV-D clones was not transmissible by the B biotype. Reassortant genomes derived from heterologous DNA components of the three isolates were infectious in all possible pairwise combinations, with symptom phenotype in pepper determined by the DNA-B component. Collectively, these results indicate that the three virus isolates examined may be considered distinct strains of PepGMV that have the capacity to exchange genetic material.  相似文献   

7.
ABSTRACT Five Capsicum species were tested for susceptibility to Tomato yellow leaf curl virus (TYLCV) and the mild strain of TYLCV (TYLCV-Mld). TYLCV was able to infect 30 of 55 genotypes of C. annuum, one of six genotypes of C. chinense, one of two genotypes of C. baccatum, and the only genotype of C. frutescens tested but was unable to infect the one genotype of C. pubescens tested. This is the first evidence for the susceptibility of C. baccatum, C. chinense, and C. frutescens to TYLCV. Unlike TYLCV isolates, TYLCV-Mld was unable to infect C. chinense. No host differences were observed between the Israeli and Florida isolates of TYLCV. None of the Capsicum species showed symptoms after infection with TYLCV or TYLCV-Mld. TYLCV was detected in fruits of C. annuum, but whiteflies were unable to transmit virus from fruits to plants. White-flies were able to transmit both TYLCV and TYLCV-Mld from infected pepper plants to tomato plants. Pepper plants in research plots were found infected with TYLCV at rates as much as 100%. These data demonstrate the ability of some genotypes of pepper to serve as reservoirs for the acquisition and transmission of TYLCV and TYLCV-Mld.  相似文献   

8.
The molecular and biological characterization of a begomovirus infecting the common weed Macroptilium lathyroides from Jamaica are reported. The virus showed 92% sequence identity to an isolate of Macroptilium yellow mosaic virus (MaYMV) from Cuba, but was distinct from the two other begomoviruses isolated from M. lathyroides , namely Macroptilium yellow mosaic Florida virus (80% identity) and Macroptilium mosaic Puerto Rico virus (68% identity). Hence, the Jamaican begomovirus was considered an isolate of MaYMV and called Macroptilium yellow mosaic virus -[Jamaica] (MaYMV-[JM]). In infectivity studies using cloned DNA-A and DNA-B genomic components, MaYMV-[JM] infected red kidney bean ( Phaseolus vulgaris ) and produced mild symptoms in Scotch Bonnet pepper ( Capsicum chinense ), but did not infect cabbage ( Brassica oleracea ). This information has implications for the development of strategies to control begomovirus diseases in Jamaica and elsewhere.  相似文献   

9.
The tomato chlorosis virus (ToCV), transmitted by whitefly species of the genera Bemisia and Trialeurodes in a semipersistent manner, causes significant losses in solanaceous crops including tomato (Solanum lycopersicum) and sweet pepper (Capsicum annuum). Worldwide reports of natural and experimental infection of sweet pepper plants with ToCV are contradictory, raising the question of whether the critical factor determining infection is related to the susceptibility of sweet pepper cultivars or the genetics of virus isolates. In this work, ToCV isolates obtained from different hosts and geographical origins were biologically and molecularly analysed, transmitted by B. tabaci MEAM1 and MED, and the reaction of different sweet pepper cultivars was evaluated under different environmental conditions. Brazilian ToCV isolates from tomato, potato (S. tuberosum), S. americanum, and Physalis angulata did not infect plants of five sweet pepper cultivars when transmitted by B. tabaci MEAM1. Temperatures did not affect the sweet pepper susceptibility to tomato-ToCV isolates from São Paulo, Brazil, and Florida, USA. However, sweet pepper-ToCV isolates from Spain and São Paulo, Brazil, were transmitted efficiently to sweet pepper plants by B. tabaci MEAM1 and MED. Although the results indicated that ToCV isolates from naturally infected sweet pepper plants seem to be better adapted to plants of C. annuum, phylogenetic analyses based on the complete nucleotide sequences of RNA1 and RNA2 as well as the p22 gene did not reveal significant nucleotide differences among them. Additional studies are needed to identify intrinsic characteristics of ToCV isolates that favour infection of sweet pepper plants.  相似文献   

10.
中国番木瓜曲叶病毒南宁分离物的基因组结构特征   总被引：2，自引：0，他引：2  
 从广西南宁田间表现曲叶症状的番木瓜植株上分离到病毒分离物G4,经三抗体夹心ELISA (TAS-ELISA)检测,G4与粉虱传双生病毒的抗体呈阳性反应。对G4 DNA-A全序列测定和分析表明,G4 DNA-A全长2 748个核苷酸,共编码6个ORFs。同源性比较及系统进化关系分析表明,G4 DNA-A与在亚洲发现的粉虱传双生病毒关系较近,其中与我国报道的中国番木瓜曲叶病毒(PaLCuCNV)同源性最高,达到98.0%。进一步比较发现,G4 DNA-A编码的AV1、AV2、AC1、AC2、AC3和AC4与PaLCuCNV相应ORFs的氨基酸同源性分别为98.4%、95.7%、97.5%、97.8%、94.1%和94.6%,表明G4应属于PaLCuCNV的一个分离物。G4编码的ORFs与中国胜红蓟黄脉病毒(AYVCNV)、辣椒曲叶病毒(PepLCV)及烟草曲茎病毒(TbCSV)有较高的氨基酸同源性,可能起源于共同的祖先。利用DNA-B及卫星DNAβ的保守引物均未能从G4分离物中扩增出相应的组分。  相似文献   

11.
河北省番茄黄化曲叶病毒病的分子鉴定初报   总被引：5，自引：1，他引：4  
双生病毒是一类具有孪生颗粒形态的植物单链病毒,目前双生病毒病害已在多个国家和地区的作物上造成严重危害。近年来,我国多省报道作物上有这类病毒的发生,且有逐年加重和扩散的趋势。根据危害番茄的双生病毒DNA A序列保守区设计简并引物,对2009年4月采自河北省魏县表现叶片黄化、曲叶症状的4个番茄样品进行PCR检测,均为双生病毒阳性,对样品的扩增片断进行了克隆测序,经序列比对分析,与番茄黄化曲叶病毒（Tomato leaf curl virus,TYLCV）山东分离物（FJ646611.1）序列相似性为99.25%~99.55%,说明河北番茄黄化曲叶病由TYLCV引起。  相似文献   

12.
ABSTRACT Tomato chlorotic mottle virus (ToCMoV) is an emerging begomovirus species widely distributed throughout tomato-growing regions of Brazil. ToCMoV appears to have expanded its geographic range recently, invading tomato-growing areas that were free of begomovirus infection before 2004. We have determined the first complete genome sequence of an infectious ToCMoV genome (isolate BA-Se1), which is the first begomovirus species isolated in the northeast of Brazil. When introduced by particle bombardment into tomato, the cloned ToCMoV-[BA-Se1] DNA-A and DNA-B components caused typical chlorotic mottle symptoms. The cloned virus was whitefly-transmissible and, although it was infectious in hosts such as Nicotiana benthamiana, pepper, tobacco, and Nicandra physaloides, it was unable to infect Arabidopsis thaliana, bean, N. glutinosa, and Datura metel. Sequence and biological analyses indicate that ToCMoV-[BA-Se1] is a typical New World begomovirus sp. requiring both DNA-A and DNA-B components to establish systemic infections. Although evidence of multiple recombination events was detected within the ToCMoV-[BA-Se1] DNA-A, they apparently occurred relatively long ago, implying that recombination probably has not contributed to the recent emergence of this species.  相似文献   

13.
A viral complex causing golden mosaic and leaf distortion (rugosity) in tomato plants was obtained from viruliferous whiteflies, and named TGV-Ub1. This complex was sap-transmitted from tomato to Nicotiana benthamiana . PCR amplification using universal begomovirus primers yielded two distinct fragments for DNA-A, suggesting that the TGV-Ub1 complex comprised at least two distinct viruses. Clones corresponding to full-length viral genomes were obtained from tomato plants infected with TGV-Ub1. Comparisons of the complete sequences of clones pUb1-49 (DNA-A), pUb1-62 and pUb1-81 (both DNA-B) indicated that they constitute novel western hemisphere begomoviruses. Clones pUb1-49 and pUB1-81 have identical common regions, thus representing the cognate DNA-A and -B of a novel begomovirus, named Tomato rugose mosaic virus (ToRMV). Clone pUb1-62 has a distinct common region from ToRMV and all other geminiviruses. A cognate DNA-A for pUb1-62 was not found. Clones containing 1·8 copies of the genomic components were constructed. Infectivity assays of these clones in tomato and N. benthamiana demonstrated that the clones corresponding to ToRMV systemically infected both hosts. Symptoms were analogous to those observed when using the pure isolates obtained in this study. The combination of pUb1-49 and -62 did not result in systemic infection, indicating that these components do not form a viable virus. ToRMV was sap-transmitted from N. benthamiana to N. benthamiana , and by grafting to Solanum tuberosum and Datura stramonium . ToRMV-A and ToRMV-B were detected in plants of Nicandra physaloides and Phaseolus vulgaris , respectively, growing in nearby tomato fields, in association with distinct DNA components.  相似文献   

14.
ABSTRACT The biological and molecular properties of Tomato leaf curl Gujarat virus from Varanasi, India (ToLCGV-[Var]) were characterized. ToLCGV-[Var] could be transmitted by grafting and through whitefly transmission in a persistent manner. The full-length genome of DNA-A and DNA-B of ToLCGV-[Var] was cloned in pUC18. Sequence analysis revealed that DNA-A (AY190290) is 2,757 bp and DNA-B (AY190291) is 2,688 bp in length. ToLCGV-[Var] could infect and cause symptoms in tomato, pepper, Nicotiana benthamiana, and N. tabacum when partial tandem dimeric constructs of DNA-A and DNA-B were co-inoculated by particle bombardment. DNA-A alone also is infectious, but symptoms were milder and took longer to develop. ToLCGV-Var virus can be transmitted through sap inoculation from infected tomato plants to the above-mentioned hosts causing the same symptoms. Open reading frames (ORFs) in both DNA-A and DNA-B are organized similarly to those in other begomoviruses. DNA-A and DNA-B share a common region of 155 bp with only 60% sequence identity. DNA-B of ToLCGV-[Var] shares overall 80% identity with DNA-B of Tomato leaf curl New Delhi virus-Severe (ToLCNDV-Svr) and 75% with ToLCNDV-[Lucknow] (ToLCNDV-[Luc]). Comparison of DNA-A sequence with different begomoviruses indicates that ToLCGV-[Var] shares 84% identity with Tomato leaf curl Karnataka virus (ToLCKV) and 66% with ToLCNDV-Svr. ToLCGV-[Var] shares a maximum of 98% identity with another isolate of the same region (ToLCGV-[Mir]; AF449999) and 97% identity with one isolate from Gujarat (ToLCGV-[Vad]; AF413671). All three viruses belong to the same species that is distinct from all the other geminivirus species described so far in the genus Begomovirus of the family Geminiviridae. The name Tomato leaf curl Gujarat virus is proposed because the first sequence was taken from an isolate of Gujarat, India.  相似文献   

15.
广东黄秋葵黄脉曲叶病样中检测到烟粉虱传双生病毒   总被引：6，自引：1，他引：5  
黄秋葵是近几年来从日本和我国台湾引进的一种蔬菜作物。近期,广东的黄秋葵上发生了黄脉曲叶病。病株的典型症状表现为叶脉黄化,在叶片正面形成网络状,在叶背面叶脉肿大突起明显,病株幼叶小且向下卷曲,甚至整片幼叶黄化。植株早期被感染表现矮化。在发生黄脉曲叶病的黄秋葵田间,其病株率高达60%以上。用烟粉虱传双生病毒简并引物对随机采集的病样进行PCR检测,从这些病样中均能扩增出1条预期大小为570 bp的特异片段;基因克隆及测序分析结果表明,与该特异片段同源的均属双生病毒科菜豆金色花叶病毒属病毒DNA,其中与木尔坦棉花曲叶病毒（Cotton leaf curl Multan virus, CLCuMV）分离物G6相似性最高,为99%。这些研究结果表明,广东黄秋葵黄脉曲叶病中存在烟粉虱传双生病毒,该病害可能也是由CLCuMV侵染引起的。  相似文献   

16.
ABSTRACT Bean calico mosaic virus (BCMoV), a whitefly-transmitted geminivirus from Sonora, Mexico, was purified, and the genome components were cloned and sequenced. Purified viral fractions and cloned genome components were infectious by biolistic inoculation to bean, completing Koch's postulates for both. The B biotype of the whitefly Bemisia tabaci efficiently transmitted both native virus and progeny virus derived from cloned DNA inoculum. Host ranges of native virus and of progeny virus derived from cloned DNA were identical based upon whitefly and biolistic mediated transmission, respectively. BCMoV has a relatively wide experimental host range among begomoviruses known to infect bean, encompassing genera and species within the Fabaceae, Malvaceae, and Solanaceae. BCMoV has a bipartite genome, as do other New World begomoviruses. BCMoV DNA-A shared highest nucleotide sequence identities with squash leaf curl virus-E strain (SLCV-E) and cabbage leaf curl virus (CaLCV) at 80.1 and 80.7%, respectively. BCMoV DNA-B shared highest nucleotide sequence identity with SLCV-E at 70.7%. The common region (CR) sequences of BCMoV and SLCV-E are 73 to 76% identical; however, modular cis-acting elements within the CR involved in replication origin function and recognition are 100% conserved. Phy-logenetic analysis indicated that BCMoV DNA-A shares a most recent common ancestor with the DNA-A of two viruses that also occur in the Sonoran Desert, SLCV-E and Texas pepper virus (TPV-TAM), and CaLCV from Florida. In contrast, a phylogenetic analysis indicated that BCMoV DNA-B shares a most recent common ancestor with SLCV-E; whereas DNA-B of CaLCV clustered in a separate clade with pepper hausteco virus. Collectively, biological and molecular characteristics indicate that BCMoV is a distinct begomovirus species with the northernmost distribution of any begomovirus isolated from bean in the Americas. Furthermore, the phylogenetic relationships of begomovirus cognate components are not necessarily identical, suggesting that DNA-A and DNA-B of some begomoviruses may have different evolutionary histories.  相似文献   

17.
粉虱传双生病毒的TAS-ELISA及PCR快速检测   总被引：37，自引：5，他引：32  
 利用粉虱传双生病毒(WTGs)多克隆抗体及单克隆抗体,建立了三抗体夹心ELISA (TAS-ELISA)检测WTGs的方法,并发现了单克隆抗体SCR18可广泛用于我国WTGs的检测。利用根据WTGs基因组上基因间隔区及外壳蛋白基因保守序列设计的引物,建立了PCR特异检测WTGs的方法。对田间病样的TAS-ELISA和PCR检测表明,粉虱传双生病毒在云南省烟草、番茄和南瓜上均存在,2种方法的测定结果是一致的。  相似文献   

18.
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   

19.
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   

20.
Classification of 32 Verticillium dahliae isolates originating from 19 plant species in eight different botanical families to races and determination of host range pathogenicity were carried out. The physiological races of isolates were identified using the two differential tomato cultivars ??Belladonna?? (susceptible to both races 1 and 2 of V. dahliae) and ??Ace 55VF?? (resistant to race 1, susceptible to race 2 of V. dahliae). Among these isolates, 14 were race 2 (43.8%), 12 race 1 (37.5%) and six nonpathogenic (18.7%) on tomato. The host range pathogenicity of isolates was determined using four differential hosts (eggplant, turnip, tomato (Ve ? ) and sweet pepper). Among isolates, five were pathogenic to both eggplant and turnip (15.6%), 21 to eggplant, turnip and tomato (65.6%), five to eggplant, turnip, tomato and sweet pepper (15.6%) and one was pathogenic to eggplant, turnip and sweet pepper (3.2%). The pathogenicity of isolates on the aforementioned five hosts was investigated on the basis of external symptoms and by calculating the relative areas under disease progress curves (relative AUDPC). Results showed that eggplant was the most susceptible, followed by turnip and tomato cv. Belladonna, while sweet pepper and tomato cv. Ace 55VF were less susceptible to all the isolates used. The pathogenicity of isolates varied from highly to mildly virulent on eggplant and turnip while on Belladonna, Ace 55VF and sweet pepper it varied from highly virulent to nonpathogenic. Belladonna exhibited a similar level of susceptibility to races 1 and 2 of V. dahliae, but was more susceptible than Ace 55VF to race 2. Interestingly, the isolates originating from eggplant were clearly more virulent than those originating from tomato and black nightshade on all solanaceous plants tested.  相似文献   

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