Citrus Viroids: Symptom Expression and Effect on Vegetative Growth and Yield of Clementine Trees Grafted on Trifoliate Orange (original) (raw)
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Phytopathology, 2006
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 respons...
Plant Disease, 2009
A field-source mixture of citrus viroids was characterized and shown to contain Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd), Citrus bent leaf viroid (CBLVd), and Citrus dwarfing viroid (CDVd). Sequencing results showed that: (i) CEVd contained the PL and PR characteristic of class A variants; (ii) HSVd was a noncachexia variant; (iii) CBLVd was related to CVd-Ia variants; (iv) CDVd was a mixture of two types (CVd-IIIa and CVd-IIIb) of variants. The presence of the same type of variants in inoculated clementine (Citrus clementina ‘Nules’) and sweet orange (C. sinensis ‘Navelina’) trees on Carrizo citrange (Poncirus trifoliata × C. sinensis) rootstocks was confirmed. The effect of infection was determined by assessing the performance of infected and noninfected trees growing in the field. Infection resulted in small trees with reduced canopy, yielding a reduced crop. Fruit characteristics were also affected: (i) clementine and sweet orange fruits from infected trees were l...
Properties of Citrus Viroids: Symptom Expression and Dwarfing
International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2002
Single viroid sources were selected from the viroid collection maintained at Instituto Valenciano de Investigaciones Agrarias (IVIA) to evaluate the field performance of infected trees. The assays were conducted in Corsica and Spain using the same viroid sources. Trifoliate orange seedlings infected with Citrus exocortis viroid (CEVd) showed severe stunting, yellow blotching of the twigs and bark scaling symptoms characteristic of exocortis disease. Bark scaling and stunting were also observed when trifoliate orange was used as a rootstock. Trifoliate orange seedlings and rootstocks infected with three different variants of Citrus viroid II (CVd-II), IIa, IIb and IIc, showed characteristic bark cracks. Only CVd-IIb and CVd-IIc variants induced cachexia symptoms on Orlando tangelo seedlings and on the scion of Clementine trees grafted on trifoliate orange. Citrus viroid I (CVd-I) and especially Citrus viroid III (CVd-III) caused a considerable reduction in size of trifoliate orange seedlings also observed when this species was used as a rootstock. No bark symptoms were associated with CVd-I and CVd-III infections. Citrus viroid IV (CVd-IV) infection also caused bark cracking symptoms and size reduction on Clementine trees grafted on trifoliate orange but these effects were not apparent on trifoliate orange seedlings. The results of these studies confirm that only CEVd induces the exocortis symptoms as initially described. The bark cracking symptoms and the reduced size resulting from infection with other citrus viroids should not be equated with "exocortis".
Phytopathology, 2002
Sequential polyacrylamide gel electrophoresis analyses showed many viroid-like RNAs in samples collected from citrus trees in Japan. Reverse transcription polymerase chain reaction and sequencing analyses of the amplified fragments verified that they were derived from variants of six citrus viroids, Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd) including CVd-I-LSS (a distinct variant of CBLVd), Hop stunt viroid, Citrus viroid III, Citrus viroid IV, and Citrus viroid OS. The samples induced symptoms with variable severity in Arizona 861-S1 ‘Etrog’ citrons (Citrus medica L.) likely due to the varying accumulation patterns produced by the different viroids. Some of the symptoms caused by the samples harboring the citrus viroids other than CEVd were as severe as those caused by CEVd. Some source citrus trees showing the severe bark scaling characteristic of exocortis disease in trifoliate orange (Poncirus trifoliata (L.) Raf.) rootstocks contained only citrus viroids o...
Identification and characterization of viroids in 'Navelina ISA 315' sweet orange
Tropical Plant Pathology, 2013
To date, seven species of viroids have been described infecting Citrus. However, only Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd) and Citrus dwarfing viroid (CDVd) have been reported in this crop in Brazil. The aim of our work was to identify and characterize viroids infecting plants of 'Navelina ISA 315' sweet orange cultivar grafted on 'Rangpur' lime from field experiments located in Bebedouro, SP, that showed gumming in the bark and wood symptoms. Biological indexing was done on the indicator host 'Clemelin 1120' tangor plants that reacted with typical gumming symptoms. Viroid infection was assessed by graft-inoculation of buds from the field trees on 'Etrog' citron plants grafted on 'Rangpur' lime, followed by RNA extraction and sPAGE analysis. RNAs were subjected to RT-PCR with primers for citrus viroids. The full-length amplified products were sequenced and compared to those available in the GenBank. The trees were found to be infected with cachexia (Ca) variants of HSVd-Ca or HSVd-Ca plus CDVd. The results indicate that efforts have to be made to increase and stimulate the indexing programs, to maintain plants healthy and to develop sanitary programs focused on reducing the spread of viroids and other graft-transmissible agents.
Detection and Characterization of Citrus Viroids in Uruguay
International Organization of Citrus Virologists Conference Proceedings (1957-2010), 2000
Citrus trees in Uruguay are mainly grafted on trifoliate orange after the dissemination of citrus tristeza virus in the 1940s. Trifoliate orange is very susceptible to citrus exocortis viroid (CEVd), but the occurrence of typical rootstock symptoms are difficult to find in citrus orchards in Uruguay. Several samples from orange and grapefruit trees grafted on trifoliate orange, with dwarfing and rootstock bark scaling were chosen, as well as asymptomatic trees to determine the presence of citrus viroids. The detection of viroids was done by biological assays on Etrog citron Arizona 861, herbaceous hosts and sequential polyacryamide gel electrophoresis. Several cDNA probes labeled with 32 P or digoxigenin were tested and were hybridized with samples from different isolates collected from citrus orchards. The cDNA probe was produced from a severe Uruguayan CEVd isolate (CEVd-Uy1) which had been previously cloned and sequenced. The following citrus viroids were found: CEVd, CVd-Ia, CVd-Ib, CVd-IIa, CVd-IIIa and CVd-IIIb; no CVd-IV was found in the samples collected. Several viroid combinations were found in the same trees. Characterization of the citrus viroids is an important step for the control and prevention of these agents in Uruguayan citrus industry that is 90% grafted on a susceptible rootstock.
Viroid Diseases of Citrus in India
International Organization of Citrus Virologists Conference Proceedings (1957-2010)
Exocortis disease of citrus in India has been known to occur for more than two decades but studies on its causal viroid have not been accomplished. The results of analysis of samples showing exocortis-like symptoms in R-PAGE revealed presence of two viroid species, one belonging to Indian Tomato bunchy top viroid (ITBVd) and the other to citrus B (CVd-IIa) group of viroids. This is for the first time in India that viroids have been found infecting citrus plantings.
Journal of General Virology, 1988
Recovery of highly purified citrus cachexia viroid (CCaV) was accomplished by serial elution following CF-11 cellulose chromatography of a 2 i-LiCl-soluble nucleic acid preparation. The alternative herbaceous host, cucumber (Cucumis sativus cv. Suyo), yielded greater quantities of the viroid than the highest yielding citrus host, citron (Citrus medica cv. Etrog). A randomly primed cDNA probe to CCaV purified from cucumber reacted positively to extracts from citron and cucumber inoculated with the same isolate of CCaV. When tested against a broad range of other citrus viroids, the CCaV cDNA hybridized to only one, CV-IIa, which has been identified as the causal agent of a mild form of the citrus exocortis disease. Because of the apparent homology between the nucleotide sequences of CV-IIa and CCaV, and a size difference of only five to ten nucleotides, these RNAs can be considered as members of a common subgroup of citrus viroids. These two viroids have been classified by bioassay reactions as the causal agents of two distinct types of citrus disease, an 'exocortis-like' syndrome and cachexia. The properties of and relationships between these two members of the citrus viroid II group and the definition of the exocortis and cachexia (xyloporosis) diseases are presented.