Occurrence of Citrus leprosis virus in Llanos Orientales, Colombia

In Colombia, citrus is cultivated in mostly small plantings that total 55,000 ha by approximately 25,000 farmers. Production includes 1,200 tons of fresh fruits and 60 tons of juice for domestic consumption, resulting in a net worth of US$650,000 per year. Most of the production comes from areas located between the Cordillera Occidental and Cordillera Central mountain ranges (departments of Antioquia, Caldas, Quindio, and Risaralda) near coffee plantations. The departments of Meta and Casanare, located at the east plains (Llanos Orientales), include a zone parallel (4 to 5°N, 72 to 74°W) to the east mountain range and generate approximately 10% of the total Colombian citrus production. Suspected citrus leprosis symptoms on leaves and fruits of sweet oranges (Citrus sinensis (L.) Osb.) were first observed by plant pathologists for CORPOICA (Colombian National Agricultural Research Organization) in citrus orchards in Casanare in 2003, and later in 2004, in Meta. To confirm the visual identification, leaves and fruits from Valencia sweet orange exhibiting typical lesions of leprosis were collected from several locations in the departments of Casanare (Yopal, Aguazul) and Meta (Guamal, Villavicencio, and Cumaral). Samples were fixed in cacodylate-buffered paraformaldehyde/glutaraldehyde solution and subsequently processed for examination in thin sections using electron microscopy. Samples were processed and examined at the Citrus Research and Educational Center (CREC) of the University of Florida, Lake Alfred, and the Agricultural College (ESALQ) of the Universidade de São Paulo at Piracicaba, SP, Brazil. Some leaf samples collected in Meta were also dried and used for detection of Citrus leprosis virus, cytoplasmic type (CiLV-C) by reverse transcription-polymerase chain reaction (RT-PCR) at the Centro APTA Citros Sylvio Moreira at Cordeirópolis (CAPTACSM). The RT-PCR was performed with primers that specifically amplify a fragment of the viral genome that codes for the putative cell-to-cell movement protein (1). Locations at CREC and ESALQ each observed, using electron microscopy, cell changes characteristic of CiLV-C that include short bacilliform particles in the endoplasmic reticulum and dense, vacuolated, and irregularly shaped viroplasm in the cytoplasm (2) in samples from Casanare and Meta. RT-PCR amplified cDNA fragments of the expected size for samples collected in Meta and one of the amplicons was sequenced (GenBank Accession No. DQ272491). The sequence obtained was found to have 98% nucleotide sequence identity to the Brazilian CiLV-C isolate (GenBank Accession No. AY289190.1). Mites collected from affected plants from the department of Meta were identified at ESALQ as Brevipalpus phoenicis (Geijskes), a known principal vector of CiLV-C (2). These several lines of evidence confirmed that the symptoms observed in sweet oranges at Meta and Casanare are due to the infection by CiLV-C. To our knowledge, this is the first report of this virus in Colombia. References:(1) E. C. Locali et al. Plant Dis. 87:1317, 2003, (2) J. C. V. Rodrigues et al. Exp. Appl. Acarol. 30:161, 2003.

Occurrence of Citrus leprosis virus in Llanos Orientales, Colombia

In Colombia, citrus is cultivated in mostly small plantings that total 55,000 ha by approximately 25,000 farmers. Production includes 1,200 tons of fresh fruits and 60 tons of juice for domestic consumption, resulting in a net worth of US$650,000 per year. Most of the production comes from areas located between the Cordillera Occidental and Cordillera Central mountain ranges (departments of Antioquia, Caldas, Quindio, and Risaralda) near coffee plantations. The departments of Meta and Casanare, located at the east plains (Llanos Orientales), include a zone parallel (4 to 5°N, 72 to 74°W) to the east mountain range and generate approximately 10% of the total Colombian citrus production. Suspected citrus leprosis symptoms on leaves and fruits of sweet oranges (Citrus sinensis (L.) Osb.) were first observed by plant pathologists for CORPOICA (Colombian National Agricultural Research Organization) in citrus orchards in Casanare in 2003, and later in 2004, in Meta. To confirm the visual identification, leaves and fruits from Valencia sweet orange exhibiting typical lesions of leprosis were collected from several locations in the departments of Casanare (Yopal, Aguazul) and Meta (Guamal, Villavicencio, and Cumaral). Samples were fixed in cacodylate-buffered paraformaldehyde/glutaraldehyde solution and subsequently processed for examination in thin sections using electron microscopy. Samples were processed and examined at the Citrus Research and Educational Center (CREC) of the University of Florida, Lake Alfred, and the Agricultural College (ESALQ) of the Universidade de São Paulo at Piracicaba, SP, Brazil. Some leaf samples collected in Meta were also dried and used for detection of Citrus leprosis virus, cytoplasmic type (CiLV-C) by reverse transcription-polymerase chain reaction (RT-PCR) at the Centro APTA Citros Sylvio Moreira at Cordeirópolis (CAPTACSM). The RT-PCR was performed with primers that specifically amplify a fragment of the viral genome that codes for the putative cell-to-cell movement protein (1). Locations at CREC and ESALQ each observed, using electron microscopy, cell changes characteristic of CiLV-C that include short bacilliform particles in the endoplasmic reticulum and dense, vacuolated, and irregularly shaped viroplasm in the cytoplasm (2) in samples from Casanare and Meta. RT-PCR amplified cDNA fragments of the expected size for samples collected in Meta and one of the amplicons was sequenced (GenBank Accession No. DQ272491). The sequence obtained was found to have 98% nucleotide sequence identity to the Brazilian CiLV-C isolate (GenBank Accession No. AY289190.1). Mites collected from affected plants from the department of Meta were identified at ESALQ as Brevipalpus phoenicis (Geijskes), a known principal vector of CiLV-C (2). These several lines of evidence confirmed that the symptoms observed in sweet oranges at Meta and Casanare are due to the infection by CiLV-C. To our knowledge, this is the first report of this virus in Colombia. References:(1) E. C. Locali et al. Plant Dis. 87:1317, 2003, (2) J. C. V. Rodrigues et al. Exp. Appl. Acarol. 30:161, 2003.

Transmissibility of Citrus leprosis virus by Brevipalpus phoenicis to Solanum violaefolium

Citrus leprosis virus (CiLV) constitutes one of the most important viruses in citrus in the areas where it occurs. Two morphological types of virus particles have been described from associated leprosis symptoms, nuclear (CiLV-N) and cytoplasmic (CiLV-C) (4). The CiLV-C is more common, representing more than 99% of samples collected from South and Central America (E. W. Kitajima and J. C. V. Rodrigues, unpublished). Both virus types are associated with the mite vector, Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae). So far, CiLV-C has only been naturally transmitted by these mites to citrus (3). Plants of Solanum violaefolium Schott (Solanaceae) and ornamental and sweet orange seedlings were infested with viruliferous adult female mites, colony no. 61 (GenBank Accession No. AY320027) that were previously maintained on citrus seedlings infected with CiLV-C according to Rodrigues et al. (3). Fifteen days after the mites were transferred, spotted yellowish symptoms were observed on leaves of plants of S. violaefolium and similar symptoms were observed after 25 days on citrus leaves. The symptomatic tissues were studied using transmission electron microscopy. Particles typical of CiLV-C were observed in samples from both plant species. To our knowledge, this is the first reported case of mites transmitting CiLV-C to a noncitrus host. Subsequent experiments showed that mites were able to transmit the virus between plants of S. violaefolium. Attempts to transmit the virus by mites from S. violaefolium to citrus were unsuccessful. The dsRNA viral electrophoresis profile showed differences between the two host plants. Reverse transcription-polymerase chain reaction (RT-PCR) and sequencing assays with primers designed to detect CiLV-C (2) amplified DNA fragments of the expected size and base composition. These data suggest the loss or alteration of some viral components from the Solanum sp. host that might be essential for the transmission or infection in citrus. Such a mechanism may explain why, despite the ever-increasing number of Brevipalpus-transmitted viruses in a large number of different host plant species (1), cross transmission is not common. This information shows one of the potential routes for CiLV to invade citrus orchards, and suggests one alternative host plant that allows rapid multiplication of the virus for characterization. References: (1) E. W. Kitajima et al. Exp. Appl. Acarol. 30:135, 2003. (2) E. C. Locali et al. Plant Dis. 87:1317, 2003. (3) J. C. V. Rodrigues et al. Proc. Int. Org. Citrus Virol. 174, 2000 (4) J. C. V. Rodrigues et al. Exp. Appl. Acarol. 30:161, 2003.

First Report of Citrus leprosis virus on Citrus in Santa Cruz, Bolivia

The citrus crop is rapidly expanding in the Province of Santa Cruz de la Sierra, Bolívia. Citrus, mostly planted by small growers, currently comprises approximately 15,000 ha. Sweet oranges (Citrus sinensis) and mandarins (C. reticulate) are the main citrus-types grown primarily for internal consumption. Recently, there has been an increase in incidence of leprosis-like symptoms (round to elliptic lesions on the leaves, chlorotic to necrotic lesions in young twigs, and depressed small lesions on the fruits). These symptoms were associated with infestations by the tenuipalpid mite Brevipalpus sp. To verify if Citrus leprosis virus was the causal agent of the observed symptoms, leaf and fruit samples (mostly from Valencia sweet orange) were collected from commercial groves in El Torno, 32 km south of Santa Cruz, and Yapacani and Colónia San Juan, 130 km northwest of Santa Cruz. Small fragments of these samples were placed immediately in a mixture of glutaraldehyde and paraformaldehyde in cacodylate buffer and later processed with transmission electron microscopy at ESALQ, Piracicaba, SP, Brazil. Some of the leaf samples were dried at 35°C and used for reverse transcription-polymerase chain reaction (RT-PCR) with primers that specifically amplify portions of the genome of Citrus leprosis virus, cytoplasmic type (CiLV-C) (1) at Centro APTA Citros, Cordeirópolis, SP, Brazil. Brevipalpus sp. mites were also collected and kept in 90% ethanol for further identification at the University of Florida, Gainesville and ESALQ. In the samples from the three surveyed areas, transmission electron microscopy confirmed the presence of short bacilliform particles within endoplasmic reticulum cisternae and electron dense viroplasms in the cytoplasm, typical of infection by CiLV-C (2). CiLV-C specific primers amplified DNA fragments of expected sizes in RT-PCR from dried leaf samples that came from these three localities. Direct sequencing of at least three amplicons of each sample confirmed the identity of the virus. The consensus sequence of the putative movement protein gene in samples from Yapacani and Colónia San Juan (GenBank Accessions Nos. AY960216 and AY960215, respectively) were identical and exhibited 99% nucleotide and 98% amino acid homology with the Brazilian isolate sequence available at GenBank (Accession No. AY289190). The consensus sequence of the putative replicase gene found in the sample from El Torno (GenBank Accession No. AY960214) exhibited 96 and 93% nucleotide and amino acid homology, respectively with the Brazilian isolate (GenBank Accession No. AY289191). Sampled mites were identified as B. phoenicis (Geijskes), the known vector of CiLV-C (2). The symptomatology, particle morphology and cytopathology, detection by molecular methods and the association with infestation by B. phoenicis, together indicate that the foliar, stem, and fruit lesions in sweet orange observed in the Santa Cruz region were caused by CiLV-C. To our knowledge, this is the first report of this virus in Bolivia. References: (1) E. C. Locali et al. Plant Dis. 87:1317, 2003. (2) J. C. V. Rodrigues et al. Exp. Appl. Acarol. 30:161, 2003.

Serological Studies Using Polyclonal Antisera Prepared Against the Viral Coat Protein of Four Begomoviruses Expressed in Escherichia coli

Polyclonal rabbit antisera were produced to the coat protein of Bean golden mosaic virus Brazil isolate (BGMV), Cabbage leaf curl virus (CabLCV), Tomato yellow leaf curl virus (TYLCV), and Tomato mottle virus (ToMoV), all expressed in Escherichia coli by the pETh expression vector. The expressed coat protein of each virus was purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for use as an immunogen. The antisera to BGMV, CabLCV, TYLCV, and ToMoV reacted in indirect (plate-trapping) enzyme-linked immunosorbent assay (ELISA) with extracts from begomovirus-infected tissue. The antisera to BGMV, CabLCV, TYLCV, and ToMoV also reacted specifically with the test begomovirus antigens in leaf imprint blots and Western blots. The CabLCV and TYLCV antisera were used to detect Bean golden yellow mosaic virus antigens by immunogold labeling of thin sections of infected bean tissues. In tissue blot immunoassays, the TYLCV antiserum reacted well with TYLCV antigens but not with ToMoV antigens, while CabLCV antiserum reacted well with ToMoV antigens and weakly with TYLCV antigens. The results indicate that polyclonal antisera prepared to expressed begomovirus coat proteins were useful for the detection of begomoviruses in an array of assays.