scholarly journals A Survey of Citrus Viroids in Campania (Southern Italy)

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 434-434
Author(s):  
M. Malfitano ◽  
M. Barone ◽  
D. Alioto ◽  
N. Duran-Vila
Keyword(s):  
Southern Italy ◽  
Sweet Orange ◽  
Poncirus Trifoliata ◽  
Sour Orange ◽  
Campania Region ◽  
First Report ◽  
Hop Stunt Viroid ◽  
Washington Navel ◽  
Viroid Infection ◽  
Citrus Viroids

Within a certification program of citrus, a survey covering 14 citrus fields not previously screened were randomly selected in seven areas of the Campania Region of southern Italy to evaluate the presence and distribution of citrus viroids in the region. During the last 3 years, 112 trees were visually inspected and sampled including 14 ‘Navelina’, 8 ‘Washington navel’, 13 ‘Biondo Commune’, 10 ‘Tarocco’, 6 ‘Valencia late’, 1 ‘Sanguinello’, and 1 ‘Vanilla’ sweet oranges (Citrus sinensis), four sour oranges (C. aurantium), 21 ‘Commune’ and 7 ‘Monreale’ clementines (C. clementina), 8 ‘Common’ and 2 ‘Avana’ mandarins (C. reticulata), 8 ‘Ovale di Sorrento’ and 6 ‘Zagara’ lemons (C. lemon), 2 Tangelos (C. reticulata × C. paradisi), and 1 grapefruit (C. paradisi). Nearly all (37 of 38) mandarin and clementine trees showed cachexia-like symptoms. Severe bark scaling that is characteristic of exocortis disease was observed on a single ‘Ovale di Sorrento’ lemon, the only tree incidentally found to be grafted onto the exocortis-sensitive trifoliate orange (Poncirus trifoliata) rootstock, since sour orange (C. aurantium) is the main rootstock used in Campania. Samples (104 of 112) that had been graft-inoculated into Arizona 861-S1 ‘Etrog citron’ (C. medica L.) on rough lemon (C. jambhiri Lush.) rootstock showed typical viroid symptoms. Viroid infection was confirmed by sequential polyacrylamide gel electrophoresis analysis (2) and molecular hybridization of imprinted membranes (1). Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd), and Citrus viroid III (CVd-III) were the most frequently detected, accounting respectively, for 67.9, 86.6, and 84.8% of the infected samples. Citrus viroid IV (CVd-IV) and Citrus bent leaf viroid (CBLVd) were found in 24.1 and 13.4% of the sources. CBLVd was detected in sweet orange (‘Tarocco’ and ‘Biondo Commune’) and lemon (‘Ovale di Sorrento’ and ‘Zagara’), while CVd-IV was detected in sweet orange (‘Tarocco’, ‘Biondo Commune’, and ‘Washington navel’), lemon (‘Ovale di Sorrento’ and ‘Zagara’), clementine (‘Commune’), and sour orange. Most trees (82.1%) were infected with more than one viroid species. The most frequent viroid combinations were CEVd + HSVd + CVd-III (40.2%), HSVd + CVd-III (16.1%), and CEVd + CBLVd + HSVd + CVd-III + CVd-IV (12.5%). To our knowledge, this is the first report of CEVd, CBLVd, HSVd, CVd-III, and CVd-IV in the Campania Region and the first report of CBLVd and CVd-IV in Italy. References: (1) A. Palacio et al. Eur. J. Plant Pathol.105:897, 2000. (2) R. F. Rivera-Bustamante et al. Anal. Biochem. 156:91, 1986.

scholarly journals Viroid Prevalence in Tunisian Citrus

Plant Disease ◽  
2004 ◽  
Vol 88 (11) ◽  
pp. 1286-1286 ◽  
Author(s):  
A. Najar ◽  
N. Duran-Vila
Keyword(s):  
Sweet Orange ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sour Orange ◽  
Citrus Industry ◽  
Stunt Viroid ◽  
Hop Stunt Viroid ◽  
Washington Navel ◽  
Viroid Infection ◽  
Csiro Publishing ◽  
The Mediterranean Basin

The citrus industry in Tunisia is based mainly on the production of local cultivars of sweet orange (Citrus sinensis), common mandarin (C. reticulata), clementine (C. clementina), and lemon (C. limon). Sour orange (C. aurantium) is the only rootstock presently being used in the major growing area located at Cap Bon where 80% of citrus is being produced. The presence of tristeza disease in the Mediterranean basin is a threat to the Tunisian citrus industry, and new rootstocks giving tristeza tolerant rootstock/scion combinations are urgently needed as an alternative to sour orange. Since some promising rootstocks are known to be sensitive to viroids (1), a survey was conducted to determine if the cultivars grown presently in Tunisia were infected with viroids. Following a preliminary report (2), an extensive survey was conducted from 1995-2001 that included 174 symptomless sources being grown at Cap Bon: 26 Maltaise demi-sanguine, 9 Maltaise sanguine, 20 Maltaise blonde, 4 orange doublefine, 16 Washington navel, 12 Valencia late, 29 common mandarin, 42 Cassar clementine, 5 Lunari lemon, and 11 Eureka lemon. These sources were graft-inoculated into Etrog citron that subsequently developed symptoms characteristic of viroid infection. Sequential polyacrylamide gel electrophoresis analysis and molecular hybridization using viroid-specific probes (1) revealed that all sources were infected with at least two viroids. Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd), and Citrus viroid III (CVd-III) were widespread and accounted for 68.4, 67.8, and 81.0% of the sources tested, respectively. Citrus bent leaf viroid (CBLVd) and Citrus viroid IV (CVd-IV) were only found in 32.7 and 2.3% of the sources. The most frequent viroid combinations were CEVd+HSVd+CVd-III (17.8%) and CEVd+CVd-III (17,2%), whereas HSVd+CVd-IV and CEVd+CBLVd+CVd-III+CVd-IV were found in a single source (0.6%). References: (1) N. Duran-Vila and J. S. Semancik. Pages 178–194 in: Viroids. CSIRO Publishing, Australia, 2003. (2) A. Najar et al. Pages 398–400 in: Proc. 15th Conf. Int. Org. Citrus Virol, 2002.

scholarly journals Citrus Viroids: Symptom Expression and Performance of Washington Navel Sweet Orange Trees Grafted on Carrizo Citrange

Plant Disease ◽  
2015 ◽  
Vol 99 (1) ◽  
pp. 125-136 ◽  
Author(s):  
N. Murcia ◽  
S. M. Bani Hashemian ◽  
P. Serra ◽  
J. A. Pina ◽  
N. Duran-Vila
Keyword(s):  
Sweet Orange ◽  
Fruit Production ◽  
Symptom Expression ◽  
Trifoliate Orange ◽  
Carrizo Citrange ◽  
Hop Stunt Viroid ◽  
Washington Navel ◽  
Canopy Volume ◽  
Viroid Infection ◽  
Orange Trees

Citrus are natural hosts of several viroid species. Citrus exocortis viroid (CEVd) and Hop stunt viroid (HSVd) are the causal agents of two well-known diseases of citrus, exocortis and cachexia. Other viroids have been found to induce specific symptoms and different degrees of stunting in trees grafted on trifoliate orange and trifoliate orange hybrids. A field assay was initiated in 1989 to establish the effect of CEVd, HSVd, Citrus bent leaf viroid (CBLVd), Citrus dwarfing viroid (CDVd), and Citrus bark cracking viroid (CBCVd) on Washington navel sweet orange trees grafted on Carrizo citrange rootstock. Here we report the effect of viroid infection on symptom expression, tree size, fruit production and quality evaluated from 2004 to 2007. Vegetative growth was affected by viroid infection with height and canopy volume being reduced. No bark scaling symptoms were observed in CEVd-infected trees albeit they presented lesions and blisters in the roots. Bark cracking symptoms were consistently observed in CBCVd-infected trees that were smaller with enhanced productivity and fruit size. No major effects were found as a result of infection with CBLVd, HSVd, or CDVd. The quality of the fruits was not affected by viroid infection, except for the low diameter of the fruits harvested from HSVd-infected trees. An interesting effect was identified in terms of tree productivity increase (yield/canopy volume) as a result of infection with CEVd, CDVd, and especially CBCVd.

scholarly journals Effect of a Field-Source Mixture of Citrus Viroids on the Performance of ‘Nules’ Clementine and ‘Navelina’ Sweet Orange Trees Grafted on Carrizo Citrange

Plant Disease ◽  
2009 ◽  
Vol 93 (7) ◽  
pp. 699-707 ◽  
Author(s):  
S. M. Bani Hashemian ◽  
P. Serra ◽  
C. J. Barbosa ◽  
J. Juárez ◽  
P. Aleza ◽  
...  
Keyword(s):  
Sweet Orange ◽  
Poncirus Trifoliata ◽  
Soluble Solids ◽  
Vitro Assay ◽  
Field Source ◽  
Carrizo Citrange ◽  
Hop Stunt Viroid ◽  
Citrus Viroids ◽  
Orange Trees

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 larger than those from noninfected trees; (ii) clementine fruits from infected trees differed in shape from those of noninfected trees; (iii) sweet orange fruits from infected trees had maturity indexes and juice contents higher than those from noninfected trees; (iv) in both species, the density of the juice, the amount of soluble solids, and the acidity of the fruits from infected trees were lower than those of fruits from noninfected trees. Infected trees had a poorly developed root system with fibrous roots containing fewer amyloplasts than noninfected trees. The results of an in vitro assay on the induction and development of roots in cultured explants are discussed.

scholarly journals Occurrence of Four Citrus Viroids in Chongqing, China

Plant Disease ◽  
2008 ◽  
Vol 92 (6) ◽  
pp. 978-978 ◽  
Author(s):  
X. F. Wang ◽  
C. Y. Zhou ◽  
K. Z. Tang ◽  
Z. A. Li
Keyword(s):  
Rapid Development ◽  
Poncirus Trifoliata ◽  
Rt Pcr ◽  
Genome Sequences ◽  
First Report ◽  
Chongqing Municipality ◽  
Rough Lemon ◽  
Hop Stunt Viroid ◽  
Two Samples ◽  
Citrus Viroids

Chongqing Municipality, located in the superior citrus belt of the upper-middle Yangtze River, is one of the most important citrus-producing areas in China. A survey was performed to evaluate the occurrence and distribution of citrus viroids in this area, where Poncirus trifoliata is the main rootstock. From 2002 to 2006, 72 samples of sweet oranges (Citrus sinensis), lemons (C. jambhiri), mandarins (C. reticulata), and mandarin hybrids, which showed stunting, bark scaling, and cracking symptoms on the rootstock, were collected and graft inoculated into Arizona 861-S1 Etrog citron (C. medica) on rough lemon rootstock and maintained in a greenhouse at 28 to 32°C. Fifty-one of the seventy-two samples were cultivars imported from abroad, and the remaining samples were all local cultivars. Sixty samples induced symptoms typical of citrus viroids on the Etrog indicator plants. To identify the causal agent(s), a one-step reverse transcription (RT)-PCR protocol, using five primer pairs (1) targeting the complete genome sequences, was used to detect Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), Hop stunt viroid (HSVd), Citrus viroid III (CVd-III), and Citrus viroid IV (CVd-IV) (2). All 72 samples were infected by citrus viroids. Sixty-five and thirty-five of the seventy-two samples were positive for HSVd and CVd-III, respectively. CEVd and CBLVd were found, respectively, in 20 and 11 of 72 samples, whereas CVd-IV was not detected. Of 72 samples, 12 without typical symptoms on Etrog citrons were infected by HSVd and CBLVd. Nearly all (70 of 72) infected citrus plants harbored more than one viroid species, and two plants were both infected by CEVd, CBLVd, HSVd, and CVd-III. RT-PCR products were purified and ligated into pGEM T-Easy Vector (Promega, Madison, WI) and three clones for each of the four viroid species were sequenced and deposited in GenBank: CEVd (Accession Nos. EU382202, U382203, and EU382204); CBLVd (Accession Nos. EU382211, EU382212, and EU382213); HSVd (Accession Nos. EU382208, EU382209, and EU382210); and CVd-III (Accession Nos. EU382205, EU382206, and EU382207). BLAST analysis showed that these nucleotide sequences had greater than 94% nucleotide identity to the most similar genome sequences in GenBank. Sweet orange was more frequently infected by viroids than the other citrus cultivars. To our knowledge, this is the first report of CBLVd, HSVd, and CVd-III in Chongqing and the first report of CBLVd in China. The high incidence of citrus viroids in Chongqing necessitates rapid development of a system of propagation and testing to reduce the incidence of viroids and the associated loss of citrus production. References: (1) L. Bernard and N. Duran-Vila. Mol. Cell. Probes 20:105, 2006. (2) K. Z. Tang et al. Acta Hortic. Sin. 32:408, 2005.

scholarly journals Detection of Multiple Infections of Citrus exocortis viroid, Citrus viroid III, and Hop stunt viroid Variants in Hunan Province, China

Plant Disease ◽  
2007 ◽  
Vol 91 (9) ◽  
pp. 1205-1205 ◽  
Author(s):  
S. Rizza ◽  
A. Catara ◽  
X. F. Ma ◽  
Z. Deng
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Leaf Roll ◽  
Poncirus Trifoliata ◽  
Hunan Province ◽  
Variable Degree ◽  
Rt Pcr ◽  
Stunt Viroid ◽  
Citrus Exocortis Viroid ◽  
Hop Stunt Viroid ◽  
Citrus Viroids

Citrus cultivation in China has increased since the late 1970s, with China now having the largest area of citrus in culture in the world that is spread in 22 provinces and municipalities. Hunan Province has undergone a program to become one of the major citrus producers in China. Poncirus trifoliata is the main rootstock, so citrus viroids are a limiting factor for further citriculture development. In mainland China, only the presence of Citrus exocortis viroid (CEVd) has been reported from Etrog citron indexing, sPAGE (sequential polyacrylamide gel electrophoresis) analysis (2), and reverse transcription (RT)-PCR (3). Three viroid-like RNAs, a1, b1, and d, based on sPAGE patterns were detected years ago in our laboratory in budsticks received from Sichuan Province. To identify different viroids and determine their distribution, a survey has been undertaken. Field trees showing stunting, bark scaling and cracking of the rootstock, and poor yield were tested using biological indexing and PCR for the most frequent citrus viroids. Samples from six trees of a local sweet orange variety and three of a Clementine variety introduced from abroad, both grafted on P. trifoliata and showing a variable degree of bark scaling and cracking, were collected near Changsha and in the County of Xin Ning at the end of summer 2006. Small pieces of bark were inserted in stems of young E. citron budwood grafted on rough lemon and maintained in a warm greenhouse (24 to 32°C). Indexing on E. citron showed mild epinasty and leaf roll typical of citrus viroid infections. To identify specific viroids, bark was ground to a fine powder with liquid nitrogen and total RNA was extracted with TRIZOL Reagent (Invitrogen, San Diego, CA) and tested by RT-PCR to detect CEVd, Hop Stunt viroid (HSVd), and Citrus viroid III (CVd-III), as well as to identify the cachexia variants of HSVd. Four primer pairs were used to test the RNA extracts by RT-PCR (1). All samples were infected by HSVd, eight with CVd-III, and six with CEVd. The cachexia variants of HSVd were detected in four of nine samples. Mixed infections were as follows: one sample had CEVd and HSVd, eight had HSVd and CVd-III, and five were infected by the three viroids. A second sampling 3 months after inoculation gave the same amplification patterns. The results show that at least three viroids are present in citrus orchards in Hunan Province. To our knowledge, this is the first report of cachexia variants of HSVd and CVd-III in China. The common occurrence of these viroids supports the need for proper indexing of mother trees and a specific shoot tip grafting program to create healthy budwood sources to provide healthy plants. References: (1) L. Bernard and N. Duran-Vila. Mol. Cell. Probes, 20:105, 2006. (2) L. Han et al. Viroids. CSIRO Publishing, Melbourne, 283, 2003. (3). Q. Hu et al. Acta Bot. Sin. 39:613, 1997.

scholarly journals Horticultural Evaluation of New Citrus latipes Hybrids as Rootstocks for Citrus

HortScience ◽  
2009 ◽  
Vol 44 (3) ◽  
pp. 595-598 ◽  
Author(s):  
Giuseppe Reforgiato Recupero ◽  
Giuseppe Russo ◽  
Santo Recupero ◽  
Roberto Zurru ◽  
Bruno Deidda ◽  
...  
Keyword(s):  
Fruit Quality ◽  
Female Parent ◽  
Poncirus Trifoliata ◽  
Growth And Yield ◽  
Sour Orange ◽  
Trifoliate Orange ◽  
Plant Yield ◽  
Volkamer Lemon ◽  
Washington Navel ◽  
Swingle Citrumelo

In 1968, the CRA-Research Center for Citriculture and Mediterranean Crops (CRA-ACM) started a research program aimed at breeding citrus rootstocks. The monoembryonic species C. latipes (Swing.) Tan. was used as the female parent; trifoliate orange [Poncirus trifoliata (L.) Raf.], sour orange, and volkamer lemon (C. volkameriana Pasq.) were used as male parents. The behavior of some of these hybrids tested with other standard rootstocks in Sicily and Sardinia was evaluated. The cultivars under comparison included ‘Washington’ navel orange and ‘SRA 92’ clementine in Sardinia and ‘Tarocco’ orange in Sicily. Our results showed the dramatic influence of rootstock on plant growth and yield; only minor effects on fruit quality were observed. Among the standard rootstocks tested, Swingle citrumelo provided the highest yield. Some of the tested hybrids (F5 P12, F6 P12, and F6 P13) may improve plant yield, thus maintaining good fruit quality. Encouraging data obtained with these hybrids may justify the use of monoembryonic species of the Papeda subgenus for breeding citrus rootstocks.

scholarly journals Performance of ‘Valencia’ Sweet Orange Trees on 12 Rootstocks at Two Locations and an Economic Interpretation as a Basis for Rootstock Selection

HortScience ◽  
2010 ◽  
Vol 45 (4) ◽  
pp. 523-533 ◽  
Author(s):  
William S. Castle ◽  
James C. Baldwin ◽  
Ronald P. Muraro ◽  
Ramon Littell
Keyword(s):  
Financial Analysis ◽  
Sweet Orange ◽  
Poncirus Trifoliata ◽  
Soluble Solids ◽  
Juice Quality ◽  
Sour Orange ◽  
Central Florida ◽  
Carrizo Citrange ◽  
Acid Ratio ◽  
Fruit Samples

Two field experiments with ‘Valencia’ sweet orange [Citrus sinensis (L.) Osb.] trees propagated on 12 rootstocks were conducted in commercial orchards. The objectives were to compare rootstock horticultural performance between two locations with soils representative of the Central Florida Ridge (AP) and coastal flatwoods (I), the major citrus-growing regions in Florida, and to see if financial analysis would provide an improved basis for interpreting rootstock performance. The randomized complete-block trials involved six-tree plots replicated eight or 10 times at planting densities of 358 trees (AP) or 252 trees (I)/ha, respectively. Tree growth and survival, yield, and juice quality were measured for 15 years. When losses occurred, trees were replaced annually with another one on the same rootstock. The data of seven rootstocks were subjected to a financial interpretation of three scenarios: tree loss and tree loss with or without tree replacement using the discounted cash flow and internal rate of return methods at a 15% rate. At the flatwoods location, when differences among replications became apparent on several rootstocks, soil data were collected to study its possible association to tree performance; also in this trial, 400-kg fruit samples were differentially harvested in 2 successive years from mature trees on each of five commercial rootstocks when the juice soluble solids/acid ratio was near 15. The juice was extracted, pasteurized, and evaluated for flavor by an experienced taste panel. The horticultural data obtained for trees on specific well-studied rootstocks [Volkamer (C. volkameriana Ten. & Pasq.)] and rough (C. jambhiri Lush.) lemons, Carrizo citrange [C. sinensis × Poncirus trifoliata (L.)], sour orange [C. aurantium (L.)], Cleopatra mandarin (C. reshni Hort. ex Tan.), trifoliate orange (P. trifoliata), a selection of sweet orange (C. sinensis), and Swingle citrumelo (C. paradisi Macf. × P. trifoliata) at both locations were typical of their well-documented performance in Florida and elsewhere. Tree losses were virtually only from citrus blight and ranged from none (sour orange) to greater than 50% (Volkamer and rough lemons) at both locations, although tree loss began later at the Central Florida location. ‘Valencia’ cuttings (only at the flatwoods site) were long-lived and cropped well for their smaller size compared with the budded trees. Taste panelists were not able to distinguish differences over two seasons among pasteurized ‘Valencia’ juices produced from trees on different rootstocks and normalized by soluble solids/acid ratio. Yield and planting density were the main factors affecting financial outcome; also, in the highly variable soils of the coastal flatwoods, trees growing in sites with greater depth to an argillic layer had 30% to 200% higher yields. Trees on Volkamer lemon had only ≈50% survival at both locations but had the highest ($7,338/ha I) or one of the highest cash flows ($13,464/ha AP) as compared with one of the commercial standards, Carrizo citrange ($6,928 I; $16,826 AP), which had only ≈25% tree loss. Inclusion of financial analysis, with certain limitations, was concluded to considerably improve rootstock selection decisions compared with selection based only on horticultural data.

Growth, yield and fruit composition of Washington Navel and Late Valencia orange trees, as affected by rootstock and root temperature

1977 ◽  
Vol 17 (85) ◽  
pp. 336
Author(s):  
PR Cary ◽  
PGJ Weerts
Keyword(s):  
Sweet Orange ◽  
Growth Yield ◽  
Poncirus Trifoliata ◽  
The Other ◽  
Root Temperature ◽  
Rough Lemon ◽  
Washington Navel ◽  
C 30 ◽  
Increasing Temperature ◽  
Orange Trees

Wahington Navel and Late Valencia scions were budded onto three clonal rootstocks (rough lemon, sweet orange and Poncirus trifoliata) mist propagated and grown in sand. The six scion/rootstock combinations were grown in containers in a glasshouse with three root temperature treatments (19�C, 25�C, 30�C). Juvenile characteristics, evident for 5-6 years when scions are budded onto seedling rootstocks, were less marked when clonal rootstocks were used. Highest yield of fruit was produced by Late Valencia/sweet orange. This yield was 30 per cent better than previously obtained with Late Valencia grown from rooted cuttings under similar conditions. The yield from Washington Navel/sweet orange was about 30 per cent less than from Late Valencia/sweet orange; and the yields from the other scion/rootstock combinations were about 50 per cent of that from Washington Navel/ sweet orange. For most combinations more total dry matter was produced at a root temperature of 25�C than at 19�C, but there was little benefit from increasing temperature to 30�C. With either scion on rough lemon, fruit abscission was marked if root temperature treatments were imposed early (in late August). The effect was particularly severe at 25� and 30�C. Root temperature treatments for the other rootstocks were not imposed until mid-October when fruitlets were about 15 mm in diameter; under these conditions there was negligible fruit drop.

scholarly journals Multiple Citrus Viroids in Citrus from Japan and Their Ability to Produce Exocortis-Like Symptoms in Citron

2002 ◽  
Vol 92 (5) ◽  
pp. 542-547 ◽  
Author(s):  
Takao Ito ◽  
Hiroyuki Ieki ◽  
Katsumi Ozaki ◽  
Toru Iwanami ◽  
Kenji Nakahara ◽  
...  
Keyword(s):  
Polyacrylamide Gel Electrophoresis ◽  
Poncirus Trifoliata ◽  
Trifoliate Orange ◽  
Chain Reaction ◽  
Hop Stunt Viroid ◽  
Citrus Viroids ◽  
Citrus Medica ◽  
Polymerase Chain ◽  
Scaling Characteristic ◽  
Citrus Trees

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 other than CEVd in complex. This indicates that certain exocortis-like diseases in Japan were caused by some combination of citrus viroids not including CEVd.

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