CITRUS TRISTEZA (CITRUS TRISTEZA VIRUS): A SERIOUS THREAT TO THE MEDITERRANEAN CITRUS INDUSTRY

This document is one in a series designed to provide important information on the causal agent, symptoms, and transmission of exotic citrus diseases. This information can be used as an educational tool to raise awareness about these diseases and for scouting and identification efforts. Disseminating information about the diseases to the citrus industry may prevent their introduction and spread in Florida. This document will focus on the exotic viral disease caused by isolates of citrus tristeza virus–stem pitting (CTV-SP). Original version: Chung, Kuang-Ren, and Ronald Brlansky. 2006. “Citrus Diseases Exotic to Florida: Citrus Tristeza Virus– Stem Pitting (CTV-SP)”. EDIS 2006 (7). https://doi.org/10.32473/edis-pp149-2006.

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The First Citrus tristeza virus Outbreak Found in a Relevant Citrus Producing Area of Sicily, Italy

Plant Disease ◽

10.1094/pdis.2003.87.3.314a ◽

2003 ◽

Vol 87 (3) ◽

pp. 314-314 ◽

Cited By ~ 10

Author(s):

S. Davino ◽

M. Davino ◽

A. Sambade ◽

M. Guardo ◽

A. Caruso

Keyword(s):

Citrus Tristeza Virus ◽

Polyclonal Antibodies ◽

Accurate Estimation ◽

Enzyme Linked Immunosorbent Assay ◽

Sour Orange ◽

Citrus Industry ◽

Aphid Vectors ◽

History Of ◽

Tristeza Virus ◽

Citrus Tristeza

In the course of a survey to select superior old citrus lines in the area of Siracusa (Sicily, Italy), trees in several blocks of Fortune (Citrus reticulata Blanco), Nova (C. reticulata Blanco), Satsuma (C. unshiu (Macfad.) mandarins Marc.), and Marsh grapefruit (C. paradisi Macfad.) propagated on sour orange (C. aurantium L.) rootstock showed stunting, decline, dieback, and small-sized fruits. Stunting was particularly evident in grapefruit. Declined plants consistently showed pin-holing in the cambial face of sour orange bark below the bud union line, which is often associated with Citrus tristeza virus (CTV) infection. Young shoots from 600 Fortune, 300 Nova, 400 Satsuma, and 20 Marsh grapefruit plants showing decline were analyzed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) (Loewe Phytodiagnostica Biochemica, Sauerlach, Germany) and by immunoprinting-ELISA (Agritest Srl Valenzano-Bari-Italy) using CTV specific polyclonal antibodies. All decline tree samples reacted positively with both techniques while healthy greenhouse controls were negative. Total RNA was extracted from 50 of those plants, 25 Fortune and 15 Nova mandarins, 5 Satsuma, and 5 Marsh grapefruit (Qiagen RNeasy Plant minikit, Qiagen S.P.A., Milan, Italy), and tested in reverse transcription-polymerase chain reaction (RT-PCR) using specific primers for genes p20 (forward 5′-CGA GCT TAC TTT AGT GTT A-3′ from CTV T36 genomic position 17767-17786 and reverse 5′-TAA TGT CAA ACT GAC CGC from CTV T36 position 18269-18286) and p23 (forward 5′-ACT AAC TTT AAT TCG AAC A-3′ from CTV T36 position 18347-18286 and reverse 5′-AAC TTA TTC CGT CCA CTT C-3′ from CTV T36 position 19026-19044) (2). In all cases, DNA fragments of the expected size were amplified. Equivalent samples from CTV-free greenhouse control plants did not react in ELISA and yielded no DNA after amplification with the same primers. When the history of the plants in the affected blocks was traced, it was found that all Fortune, Nova, satsuma and Marsh grapefruit trees had been propagated from budwood illegally imported from Spain 10 years before, suggesting the possibility that the imported buds were infected with CTV. The estimated number of infected plants in the area of Siracusa is approximately 10,000, and some evidence suggests that the virus might be spreading in the area (work in progress). Only scattered CTV-infected trees had been detected in Italy previously (1). To our knowledge, this is the first report of an important CTV outbreak in Italy. Additional surveys are being conducted to get a more accurate estimation of the CTV incidence, to determine if the virus is being dispersed by aphid vectors, and to biologically and molecularly characterize the virus strains present in the affected area. Presently, there are approximately 100,000 ha of citrus in Sicily, mostly grown on decline susceptible sour orange rootstock. The presence and potential spread of CTV is a major threat for this citrus industry. References: (1) M. Davino and G. Terranova. Frutticoltura 61:18, 1999. (2) A. Sambade et al. Plant Pathol. 51:257, 2002.

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Occurrence of Stem-Pitting Strains of Citrus tristeza virus in Croatia

Plant Disease ◽

10.1094/pd-89-0342b ◽

2005 ◽

Vol 89 (3) ◽

pp. 342-342 ◽

Cited By ~ 2

Author(s):

S. Černi ◽

D. Škorić ◽

M. Krajačić ◽

Ž Gatin ◽

C. Santos ◽

...

Keyword(s):

Mediterranean Basin ◽

Citrus Tristeza Virus ◽

Enzyme Linked Immunosorbent Assay ◽

Cp Gene ◽

Plant Pathol ◽

The Mediterranean ◽

Tristeza Virus ◽

Stem Pitting ◽

The Mediterranean Basin ◽

Citrus Tristeza

Citrus is grown in Croatia (approximately 1,500 ha of citrus groves) on the Dalmatian Coast and Islands between 42 and 43°30′N. The major species, Citrus unshiu Marc. (Satsuma mandarin), is grafted on trifoliate rootstock. The presence of Citrus tristeza virus (CTV) in Satsumas in the Neretva Valley Region was previously reported (3). During the course of a biomolecular characterization of isolates from Croatia, 15 budsticks were collected from field-infected, enzyme-linked immunosorbent assay (ELISA)-positive sources during the autumn of 2003 near Kaštela, Split, Metković (Neretva Valley), and on the island of Vis. Isolates were propagated by graft transmission to Madam Vinous sweet orange (SwO) and maintained in an insect-proof greenhouse at 21 to 33°C. Eight months later, the bark of terminal twigs was peeled off, and the wood was examined for the occurrence of pits. Typical tristeza stem-pitting (SP) was observed in four isolates originating from cvs. Fukumoto navel, Washington navel, and Ichimaru Satsuma and C. wilsonii. The bark from the infected sources was analyzed using immunocapture reverse transcription-polymerase chain reaction (RT-PCR) with primers CTV1 and CTV10 (1), targeting the whole coat protein (CP) gene. The PCR products of the expected size (669 nucleotides) were obtained and TA cloned (pGEM-T Easy Vector; Promega, Madison, WI) in E. coli cells. Thirty-two clones harboring the CTV CP gene were sequenced. Two of the SP isolates contained four genomic variants that differed an average of 2.0% from the severe SwO SP strains SY568 and Nuaga (4) from California and Japan, respectively. The other two SP isolates contained four variants that differed as little as 1.6% from the severe SwO SP from India, CTV-Puna, and CTV-Bangalore (2). The net average distance between these two clusters of sequences is 5.2%. One sequence from each of the four SP isolates was deposited in GenBank (Accession Nos. AY791841 to AY791844). These findings were confirmed by direct observation of SP symptoms in a Satsuma orchard in the Neretva Valley during the spring of 2004. No other conspicuous symptoms that could be attributed to CTV were observed in the field. Most Satsumas were introduced to the Neretva Region from Japan between 1964 and 1984. Together with the fact that the related Nuaga strain was also isolated from Satsumas in Japan (4), our results suggest that SwO SP strains were introduced into Croatia at the same time and have been spreading for several decades. It has been generally believed that this kind of CTV strains either do not exist in the Mediterranean basin or, when found (e.g., Spain), are immediately eradicated. The findings reported here suggest that the epidemiological scenario for the Mediterranean Basin requires revision. References: (1) G. Nolasco et al. Eur. J. Plant Pathol. 108:293, 2002. (2) A. Roy et al. Arch. Virol. 148:707, 2003. (3) A. Šarić and I. Dulić. Agric. Conspectus Sci. 55:171, 1990. (4) G. Suastika et al. J. Gen. Plant Pathol. 67:73, 2001.

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