UC Riverside International Organization of Citrus Virologists Conference Proceedings (1957-2010) Title Viroid Diseases of Citrus in India Publication Date (original) (raw)
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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.
A Definition of Citrus Viroid Groups and Their Relationship to the Exocortis Disease
Journal of General Virology, 1988
Nucleic acid extracts from citrons (Citrus medica cv. Etrog) displaying mild and moderate symptoms associated with the exocortis disease were analysed by sequential and denaturing PAGE which revealed the presence of several viroids. A comparison was made of electrophoretic patterns displaying one or more distinct citrus viroids from field isolates of citrus with exocortis. Citrus viroids were characterized by the physical parameters of electrophoretic mobility, chromatography on CF-11 cellulose and hybridization to cDNA probes of the well characterized citrus viroids, citrus exocortis viroid, CV-Ib from the 'citron variable viroid' isolate, and citrus cachexia viroid. These characteristic properties combined with biological distinctions in the host range and symptom expression suggested a scheme for the organization of the citrus viroids into five major groups. The association of the symptoms induced by these citrus viroids in citron cv. Etrog, their organization into individual viroid groups and their presumed relationship to the exocortis disease of citrus are discussed.
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...
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.
A Viroid Different from Citrus Exocortis Viroid Found in Commercial Citrus in Sicily
International Organization of Citrus Virologists Conference Proceedings (1957-2010)
A low molecular weight RNA, named citrus "B" viroid (CBV), has been detected alone or associated with citrus exocortis viroid (CEV) in many commercial citrus species and varieties. The electrophoretic mobility of CBV on 5% polyacrylarnide gels under denaturing conditions is between those of CEV and the fast form of coconut cadang cadang viroid (CCCV) RNA1. CBV replicates in zucchini squash, a common host for CEV, but not in ten other herbaceous hosts of CEV. Citrus nucleic acid extracts containing CBV were reacted with full-length CEV-, potato spindle tuber viroid (PSTV)-cDNA probes and with CEV-, PSTV-, tomato apical stunt viroid (TASV)-and tomato planta macho viroid (TPMV)-RNA probes. CBV did not hybridize with any of the probes. Inoculations of partially purified CBV onto different citrus indicator plants gave variable epinasty on Etrog citron, but no symptoms in other indicators.
Nucleic Acids Research, 1987
The primary structure of a grapevine viroid (GVs) isolated in Spain was determined. The sequence consisted of 369 nucleotide residues forming a circular molecule. GVs presented extensive homology with viroids of the potato spindle tuber viroid (PSTV) group, that was specially high in the case of citrus exocortis viroid (CEV) both with variants found in isolates inducing severe (92* with CEV-A) and mild (89* with CEV-DE26) symptoms on tomato. The secondary structure proposed for GVs showed that the changes in the sequence in relation to CEV-A generated modifications of the secondary structure particularly Important in the left terminal (Tl), variable (V) and pathogenesis (P) viroid domains that have been postulated. Nevertheless it was noted 1n GVs a central core in the P domain that is conserved in the class A sequence variants characteristic of severe isolates, but not 1n the class B ones found in mild isolates of CEV. These observations indicate that GVs should be considered as a severe isolate of CEV from grapevine (CEV-g), a suggestion that correlates with the biological properties of CEV-g both in tomato and in Gynura aurantiaca. The presence of this central core in the P domain seems to characterize alI the variants of CEV Inducing severe symptoms in tomato.
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".
Crop Protection, 2019
Citrus exocortis viroid (CEVd) is the causal agent of exocortis disease, the economically important viroid disease of citrus. In this research, CEVd copy number was quantified in sour orange (Citrus aurantium L.) and citrange (Poncirus trifoliata L. Raf. × Citrus sinensis L.) seedlings by absolute real-time PCR. A full-length in vitro transcript of a single-sequence CEVd-S1 variant was synthesized and mechanically inoculated into sour orange and Troyer citrange seedlings as tolerant and sensitive hosts, respectively. CEVd copy number was subsequently monitored at different times after inoculation in the green bark of infected seedlings for up to 16 weeks post inoculation (wpi). CEVd was detected at 3 wpi and totally increased up to 16 wpi. The copy number of CEVd per milligram of bark tissue in both host species was in the range of 10 3 to 10 4 at the third and sixth weeks post inoculation, without any significant differences. Although the viroid titer was remarkably higher in citrange (sensitive host) than in sour orange (tolerant host) at 10-16 wpi, we demonstrated that CEVd titer differed in citrus species depending on the time of sampling and host plant species.
2022
1. Background Citrus plants are prone to infection by different viroids which deteriorate their vigor and production. Citrus viroid V (CVd-V) is among the six citrus viroids, belongs to genus Apscaviroid (family Pospiviroidae) which induces symptoms of mild necrotic lesions and cracks. II. Methods and ResultsA survey was conducted to evaluate the prevalence of CVd-V in core and non-core citrus cultivated areas of Punjab, Pakistan. A total of 154 samples from different citrus cultivars were tested for CVd-V infection by RT-PCR. The results revealed 66.66% disease incidence of CVd-V. Citrus cultivars Palastinia Sweet lime, Roy Ruby, Olenda Valencia, Kaghzi lime, and Dancy were identified as new citrus hosts of CVd-V for the first time from Pakistan. The viroid infection was confirmed by biological indexing on indicator host Etrog citron. The reported primers used for the detection of CVd-V did not amplified, rather showed non-specific amplification, which led to the designing of new p...