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1.
Vernière C Perrier X Dubois C Dubois A Botella L Chabrier C Bové JM Vila ND 《Phytopathology》2006,96(4):356-368
ABSTRACT Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), a noncachexia variant of Hop stunt viroid (HSVd), Citrus viroid III (CVd-III), and Citrus viroid IV (CVd-IV) were co-inoculated as two-, three-, four-, and five-viroid mixtures to Clementine trees grafted on trifoliate orange to evaluate their effect on symptom expression, tree growth, and fruit yield. Most trees infected with CEVd-containing viroid mixtures developed exocortis scaling symptoms, as did CEVd alone, whereas most trees infected with HSVd- or CVd-IV-containing mixtures developed bark-cracking symptoms. Trees infected with mixtures containing both CEVd and CVd-IV revealed the existence of antagonism between these two viroids in terms of the expected bark-scaling and cracking symptoms. Synergistic interactions also were identified in trees infected with certain viroid combinations that, in spite of lacking CEVd, expressed exocortis-like scaling symptoms. Viroid interactions also affected the expected response of trees in terms of vegetative growth and fruit yield. Trees infected with viroid combinations containing CEVd or CVd-III were smaller and produced less fruit than trees infected with mixtures not containing these viroids. Viroid interactions on scion circumference and cumulative fruit yield, in terms of additivity of their effects, were statistically confirmed using a factorial analysis of variance model with two mean estimation approaches. In single-viroid infections, CEVd, CVd-III, and, to a lesser extent, CBLVd consistently and significantly reduced tree size and fruit yield. Conversely, HSVd and CVd-IV slightly increased fruit yield and reduced scion circumference. Rare and not consistent significant interactions were detected with the five-, four-, and three-viroid combinations. Antagonistic interactions between CEVd and CVd-III or CBLVd and CVd-III were revealed over the years with consistent significance. The antagonistic interaction between CEVd and CVd-IV was highly significant over the years when additional viroids were present; however, this antagonism appeared much later in the case of an exclusive interaction. HSVd and CVd-IV showed a consistent and significant synergistic interaction on yield only when both viroids were exclusively present. These results demonstrate antagonistic or synergistic relationships between citrus viroids depending on the viroid mixtures present in the host. 相似文献
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J. Wang I. N. Boubourakas A. E. Voloudakis T. Agorastou G. Magripis T. L. Rucker P. E. Kyriakopoulou G. Vidalakis 《European journal of plant pathology / European Foundation for Plant Pathology》2013,137(1):17-27
Seventy four percent of the budwood tree sources samples from the Greek national citrus germplasm foundation collection were positive for one or more viroids. Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd), the two potentially damaging viroids for the Greek citriculture, especially after transitioning to Citrus tristeza virus resistant/tolerant rootstocks and scions, were detected along with Citrus bark cracking viroid, Citrus bent leaf viroid (CBLVd), and Citrus dwarfing viroid (CDVd). All samples tested negative for Citrus viroid V (CVd-V), CVd-VI and CVd-I-LSS (CBLVd variant). An HSVd isolate related to the non-cachexia variant contained two critical cachexia-related nucleotide changes, while two more isolates were unique among the previously reported HSVds. Unusual CDVd isolates with altered RNA secondary structure were identified in trees additionally co-infected with CEVd and HSVd. Budwood sources that had previously undergone therapy tested negative for all targeted viroids, suggesting that budwood sources in Greece can be protected against graft-transmissible pathogens, even under severe inoculum pressure. Therapied and tested citrus propagative material requires a comprehensive program not available currently in Greece, involving regulators, scientists, and the private sector, for the establishment and successful operation of a national citrus germplasm collection. 相似文献
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Xuefeng Wang Changyong Zhou Kezhi Tang Yan Zhou Zhongan Li 《European journal of plant pathology / European Foundation for Plant Pathology》2009,124(1):175-180
Citrus plants are natural hosts of five viroid species and large numbers of sequence variants. In this paper a simple and
sensitive one step multiplex RT-PCR protocol with an internal control was utilised to simultaneously detect and differentiate
five citrus viroids: Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), Hop stunt viroid (HSVd), Citrus viroid-III (CVd-III) and Citrus viroid-IV (CVd-IV). In addition, a micro and rapid total nucleic acid extraction method was developed and the protocol applied to evaluate
the occurrence and distribution of citrus viroids in China. 相似文献
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Arizona 861-S1 citron ( Citrus media L.) infected with a severe exocortis isolate containing four citrus viroids was used as source of tissue for shoot-tip grafting in vitro. Out of 51 attempts, 25 successful grafts were obtained. Only 16 plants survived transplanting and of these 12 were viroid-free. The viroid profile of the other four plants showed fewer viroids than the original field source. The significance of these results, as compared with previous reports on the recovery of viroid-free plants, is discussed. The results show the usefulness of shoot-tip grafting in vitro as a tool to recover single viroid isolates from complex field sources. 相似文献
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Oded Cohen Ozgur Batuman Yoni Moskowits Alexander Rozov Elisha Gootwine Munir Mawassi Moshe Bar-Joseph 《Phytoparasitica》2005,33(2):141-148
Mechanical inoculations with contaminating tools and propagation of infected budwood were considered the main causes for the
omnipresence of multiple viroid species among citrus and other Middle Eastern and Mediterranean fruit trees and grapevines.
However, neither means could explain viroid infections of wild trees — scattered on terrains inaccessible to humans — nor
the finding of similar viroids among graft-incompatible plants. Northern hybridization of RNA extracts made of scrapings from
the surfaces of goat (Capra hircus) horns that were rubbed against etrog (Citrus medica) stems infected with a citrus viroids complex, revealed accumulation of considerable amounts ofCitrus exocortis viroids (CEVd) andHop stunt viroids (HSVd). Experimental transmission of both CEVd and HSVd was obtained by rubbing healthy citrus plants with goat horns that
had been rubbed 24 h earlier on infected etrog stems. These results implicate goats as possible vectors of viroids. Transmissionvia goats could have facilitated the long-range spread of viroids among cultivated and wild plants andvice versa and also among graft-incompatible plants. 相似文献
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Four viroids were isolated in crops of tomato, eggplant, carrot and turnip. They were detected only after inoculation of 'Rutgers' tomato with nucleic acid extracts from field plants and were characterized as variants of citrus exocortis viroid (CEVd). The size of the variants ranged from 371 to 374 nucleotides and they contained nucleotide exchanges and insertions affecting all structural domains. Symptoms were induced in tomato and carrot whereas eggplant and turnip responded as symptomless carriers. As the samples came from an area where no citrus is grown, it appears that these viroids have a reproductive cycle independent of this crop, and perhaps involving wild plants or other vegetables. 相似文献
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In studies to identify genotypes resistant to infection with citrus viroids, Eremocitrus glauca and Microcitrus australis were selected because their evolution in their habitat in Australia and New Guinea may have led to the selection of unusual traits. The movement and accumulation of Citrus exocortis viroid (CEVd), Hop stunt viroid, Citrus bent leaf viroid, Citrus dwarfing viroid, Citrus bark cracking viroid and Citrus viroid V (CVd‐V) in self‐rooted as well as in graft‐ propagated E. glauca and M. australis plants was assessed by northern hybridization, RT‐PCR and by topworking to the sensitive selection 861‐S1 of Etrog citron. In both plant species the inoculated viroids were undetectable unless these plants were grafted to a susceptible Citrus partner, the rough lemon rootstock and/or the topworked Etrog citron, which acted as viroid sources. The results obtained indicate that M. australis and in particular E. glauca are poor viroid hosts in which viroid replication/accumulation does not occur or is extremely inefficient. However, viroid downward and upward movement to grafted Citrus partners in which viroid replication and accumulation occurs efficiently was not impaired. Eremocitrus glauca and M. australis showed differences regarding their properties as viroid hosts, but for both species CEVd seemed to have the lowest affinity among the viroid species tested and CVd‐V the highest. Even though E. glauca and M. australis do not appear to be truly resistant to viroid infection, they are interesting genotypes for further characterization of the mechanisms involved in viroid infection. 相似文献
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ABSTRACT Citrus exocortis viroid (CEVd) is the casual agent of citrus exocortis disease, and has been found in naturally infected citrus and noncitrus hosts. Field isolates of CEVd may infect susceptible hosts as a complex of genetically related sequence variants (haplotypes). In the present work, a CEVd isolate recovered from a symptomless broad bean plant was characterized as a heterogeneous population with a nucleotide diversity of 0.026, which did not contain a predominant haplotype. When nucleic acid extracts of this infected broad bean were used to inoculate tomato, the plants displayed symptoms and the CEVd population was more homogeneous, with a nucleotide diversity of 0.007. However, when nucleic acid extracts from this tomato isolate were back inoculated to new broad bean plants, this isolate did not revert to the original population, because it showed low nucleotide diversity (0.001) and induced symptoms in the broad bean plants. Symptomless broad bean plants may act as reservoirs of highly heterogeneous populations of CEVd variants, providing an excellent inoculum source in terms of its potential to infect a broad range of putative hosts. The epidemiological implications are discussed. 相似文献
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ABSTRACT Citrus viroid (CVd) group II is comprised of hop stunt viroid (HSVd)-related variants of 295 to 302 nucleotides. Included in this group are the cachexia-inducing agents citrus cachexia viroid (or CVd-IIb), CVd-IIc, Ca-903, and Ca-909 as well as the non-cachexia-inducing variant CVd-IIa. The cachexia indexing hosts 'Parson's Special' mandarin and 'Orlando' tangelo as well as Citrus macrophylla responded with symptoms of gumming, discoloration, and stem pitting when infected by CVd-IIb, CVd-IIc, or Ca-903. However, 'Palestine' sweet lime, the indicator host used to describe the xyloporosis disease, displayed a distinctly different fine-pitting reaction and no discoloration or gumming when infected by the same viroids. Cachexia-inducing variants contain a number of nucleotide changes more similar to hop-type HSVd sequences than to the citrus-type HSVd sequences, as typified by CVd-IIa. The nucleotide sequence of CVd-IIc was identical to CVd group II isolates common to trees expressing xyloporosis. Experimental evidence indicates that either CVd-IIb or CVd-IIc can cause citrus diseases known as cachexia and xyloporosis and that the two disease designations reflect the distinct responses of different indexing hosts to the same viroids. 相似文献
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柑橘衰退病毒(Citrus tristeza virus,CTV),柑橘碎叶病毒(Citrus tatter\|leaf virus,CTLV),柑橘裂皮病类病毒(Citrus exocortis viroid,CEVd)和柑橘黄龙病(Huanglongbing, HLB)亚洲种病原(Candidatus liberobacter asiaticus)是重要的柑橘嫁接传播病原。本文建立了同时检测HLB病菌、CTV、CEVd 和CTLV 4种柑橘嫁接病原的一步法、双温多重PCR检测技术体系,同时在体系中设置内参基因。应用该体系快速评价了4种嫁接传播病原在田间侵染情况,结果表明28个田间样品CTV、CEVd、CTLV和HLB感染率分别为89.3 %、17.9 %、10.7 %和28.6 %,接近半数样品为混合感染。并且将该方法应用于快速评价茎尖嫁接苗病毒的脱除情况。 相似文献
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ANASTASIA P. KYRIAKOU 《Plant pathology》1992,41(1):20-24
A survey for citrus exocortis viroid (CEV) was conducted in commercial groves of the main citrus-producing areas of Cyprus during 1987–1990. Of 573 trees sampled, representing 25 species and varieties, 506 (88.3%) were found to be infected when indexed by grafting to seedlings of'Etrog' citron (Citrus medica) , selection Arizona 861. Levels of infection by CEV were lower in newer introductions than in introductions made before the 1940s. In greenhouse tests, CEV was readily transmitted from citron to healthy citron and gynura (Gynura aurantiaca) by knife-blade inoculation. Retransmission of CEV from infected gynura back to citron was successful. 相似文献
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Qiong Wu Mengji Cao Huanan Su Sagheer Atta Fangyun Yang Xuefeng Wang Changyong Zhou 《European journal of plant pathology / European Foundation for Plant Pathology》2014,139(1):13-17
CVd-I-LSS (low sequence similarity), a variant of Citrus bent leaf viroid (CBLVd), was first discovered in Japan, and its distribution is currently limited to Japan and Iran. In the present study, seven CVd-I-LSS isolates were detected from different citrus hosts (Citrus sinensis, C. reticulata and C. limettioides) in Pakistan and China. Genetic diversity analysis of 49 cDNAs of CVd-I-LSS isolates showed that the Pakistan population was more diverse than that tested from Japan or China. Phylogenetic analysis clustered the predominant sequences examined into three main clades. Only sequences from the Pakistan isolates were found in all three clades, suggesting Pakistan may be the original source of CVd-I-LSS. Cultivar import records and the close phylogenetic relationship found between CVd-I-LSS from China and Japan suggested that the viroid isolated from China might have originated from Japan. 相似文献
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T. Kapari-Isaia A. Kyriakou L. Papayiannis D. Tsaltas S. Gregoriou I. Psaltis 《Plant pathology》2008,57(2):348-353
A new laboratory technique combining shoot-tip grafting in vitro and biological indexing on indicator plants was explored for the detection of citrus exocortis and related viroids. Τhree in vitro laboratory methods were used and compared with the classical biological method. With the classical in vivo method, diagnosis is based on the expression of symptoms on indicators 11–14 weeks after inoculation. In contrast, with the first in vitro method, microindexing in vitro of citron seedlings by graft inoculation, diagnosis was possible 12 days after inoculation; with the second method, microindexing in vitro of citron cuttings by graft inoculation, 20 days after inoculation; and with the third method, microindexing in vitro of citron cuttings by injection inoculation, 40 days after inoculation. Inoculated Etrog citron plantlets grown in vitro and tested by RT-PCR showed the same viroid content as the source plants. Of the three in vitro viroid indexing methods, microindexing on cuttings by grafting was easier and more reliable than microindexing either on seedlings or on cuttings by injection. 相似文献
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A. B. Sahana H. Nagaraja P. K. Maheshwar M. Y. Sreenivasa M. N. Nagendra Prasad C. R. Adkar-Purushothama 《Phytoparasitica》2014,42(4):519-527
Plant pathogens like ‘Ca. Liberibacter’, phytoplasma, viruses and viroids cause diseases to almost all economically important plants. A simple and fast sap-mediated polymerase chain reaction (PCR) method for the detection of these pathogens infecting various plant hosts is described in the present study. Sap from selected plants was drawn aseptically on parafilm, from the mid-rib of young leaves. Depending on the type of host plant, sap was diluted to optimal concentration before PCR analysis. ‘Ca. Liberibacter’, Citrus tristeza virus (CTV) and Citrus exocortis viroid (CEVd) infecting citrus, and ‘Ca. Phytoplasma’ infecting pepper and sandal trees were tested by sap-mediated PCR. The reliability of this procedure was evaluated by comparing the findings with previously described protocols. The sap-mediated nucleic acid template preparation for PCR assay is devoid of laborious nucleic acid extraction and expensive chemicals. Hence the present method is rapid, economical and so can be employed for diagnosis of large number of plant samples. 相似文献
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A. Palacio-Bielsa X. Foissac N. Duran-Vila 《European journal of plant pathology / European Foundation for Plant Pathology》1999,105(9):897-903
A method based on the hybridisation of tissue imprints was developed for routine indexing of citrus viroids. For maximum sensitivity and reliability, the inoculation of Citrus medica (Etrog citron) as a viroid amplification host is required. Hybridisation against Digoxigenin-labelled RNA- or DNA-probes followed by detection of viroid-probe hybrids using anti-DIG-alkaline phosphate conjugate and the chemiluminescence substrate CSPD was suitable for the detection of all citrus viroids with the same sensitivity as other available methods. The overall process is extremely simple and allows quick analysis of large numbers of samples by easily trained personnel and minimum equipment. 相似文献