Complete genome sequence of two tomato-infecting begomoviruses in Venezuela: evidence of a putative novel species and a novel recombinant strain.

At least six begomovirus species have been reported infecting tomato in Venezuela. In this study the complete genomes of two tomato-infecting begomovirus isolates (referred to as Trujillo-427 and Zulia-1084) were cloned and sequenced. Both isolates showed the typical genome organization of New World bipartite begomoviruses, with DNA-A genomic components displaying 88.8% and 90.3% similarity with established begomoviruses, for isolates Trujillo-427 and Zulia-1084, respectively. In accordance to the guidelines for begomovirus species demarcation, the Trujillo-427 isolate represents a putative new species and the name "Tomato wrinkled mosaic virus" is proposed. Meanwhile, Zulia-1084 represents a putative new strain classifiable within species Tomato chlorotic leaf distortion virus, for which a recombinant origin is suggested.

Complete genome sequence of jacquemontia yellow vein virus, a novel begomovirus infecting Jacquemontia tamnifolia in Venezuela.

Wild plants of the family Convolvulaceae are hosts for a few New World begomoviruses (genus Begomovirus, family Geminiviridae). In this work, we report the complete genome sequence of a new begomovirus infecting the wild convolvulaceous plant Jacquemontia tamnifolia in Venezuela. The cloned bipartite genome showed the organization of typical New World begomoviruses and was found to be phylogenetically related to those of begomoviruses from Venezuela and other Caribbean countries. Several recombination events have been shown to have occurred involving genome fragment exchange with related begomoviruses infecting crops such as tomato and cucurbits and wild plants, including Jacquemontia sp. We propose the name jacquemontia yellow vein virus (JacYVV) for this new begomovirus.

Molecular and biological characterization of a new Tomato mild yellow leaf curl Aragua virus strain producing severe symptoms in tomato.

Tomato mild yellow leaf curl Aragua virus (ToMYLCV) is a begomovirus first reported infecting tomato (Solanum lycopersicum) and milkweed (Euphorbia heterophylla) in Venezuela. In this study, a ToMYLCV isolate (Zulia-219) was completely sequenced and its host range was evaluated. The DNA-A and DNA-B components of isolate Zulia-219 showed 93 and 85% nucleotide sequence identity with the respective counterparts of the ToMYLCV type strain. According to current demarcation criteria for begomovirus species, Zulia-219 is a new strain of ToMYLCV. Interestingly, tomato plants inoculated with ToMYLCV Zulia-219 displayed severe symptoms, including severe chlorotic leaf curling, in contrast to mild symptoms associated with the type strain of this begomovirus. These results indicate potential risks associated with this new ToMYLCV strain for tomato production in Venezuela.

Complete genome sequence of Jacquemontia yellow mosaic virus, a novel begomovirus from Venezuela related to other New World bipartite begomoviruses infecting Convolvulaceae.

The complete genome of a bipartite begomovirus (genus Begomovirus, family Geminiviridae) infecting Jacquemontia sp. (Convolvulaceae) in Venezuela has been cloned and sequenced. Sequence comparison and phylogenetic analysis have shown that it represents an isolate of a novel species with closest relatives being two New World bipartite begomoviruses that infect Convolvulaceae, Jacquemontia mosaic Yucatan virus and Merremia mosaic virus. The DNA-As of these begomoviruses, however, share only 77.0-78.4 % nucleotide sequence identity with the DNA-A of the isolate described here, for which a recombinant origin is suggested. Based on the symptoms observed in the field, the name Jacquemontia yellow mosaic virus (JacYMV) is proposed for this novel bipartite begomovirus.

Complete genome sequences of two begomoviruses infecting weeds in Venezuela.

The complete sequences of isolates of two new bipartite begomoviruses (genus Begomovirus, family Geminiviridae) found infecting weeds in Venezuela are provided. The names proposed for these new begomoviruses are "Datura leaf distortion virus" (DLDV), isolated from a Datura stramonium L. (family Solanaceae) plant, and "Dalechampia chlorotic mosaic virus" (DCMV), isolated from infected Dalechampia sp. (family Euphorbiaceae) and Boerhavia diffusa L. (family Nyctaginaceae) plants. Phylogenetic analysis showed that these new begomoviruses segregated in two distinct clades of New World begomoviruses. To our knowledge, this is the first record of a begomovirus infecting Dalechampia sp. plants. Also, this is the first report of a begomovirus infecting Boerhavia spp. and Datura spp. in Venezuela.

Complete genome sequences of two novel begomoviruses infecting common bean in Venezuela.

The complete genome sequences of isolates of two new bipartite begomoviruses (genus Begomovirus, family Geminiviridae) found infecting common bean in Venezuela are provided. The names proposed for each of these viruses are "bean yellow chlorosis virus" (BYCV) and "bean white chlorosis mosaic virus" (BWCMV). Phylogenetic analysis showed that they segregated in two distinct clades of New World begomoviruses. This is the first report of begomoviruses infecting common bean in Venezuela.

Tomato chlorotic leaf distortion virus, a new bipartite begomovirus infecting Solanum lycopersicum and Capsicum chinense in Venezuela.

Virus isolate T217L was obtained from a diseased tomato (Solanum lycopersicum) plant showing leaf deformation and chlorotic mottle symptoms near Maracaibo in the state of Zulia, Venezuela. Full-length DNA-A and DNA-B molecules of T217L were cloned and sequenced. The genome organization of T217L was identical to the bipartite genomes of other begomoviruses described from the Americas. Characteristic disease symptoms were reproduced in S. lycopersicum and Capsicum annum plants inoculated using the cloned viral DNA-A and DNA-B components, confirming disease aetiology. A sequence analysis of DNA-A showed that the T217L isolate has the highest sequence identity (84%) with sida yellow mosaic Yucatan virus (SiYMYuV), sida golden mosaic Honduras virus (SiGMHV) and bean dwarf mosaic virus (BDMV) isolates. This is less than the 89% identity in the DNA-A component that has been defined as the threshold value for the demarcation of species in the genus Begomovirus. The molecular data show that isolate T217L belongs to a novel tentative begomovirus species, for which the name tomato chlorotic leaf distortion virus is proposed. TCLDV was also detected in symptomatic C. chinense plants growing near the T217L-infected plant.

Tomato Twisted Leaf Virus: A Novel Indigenous New World Monopartite Begomovirus Infecting Tomato in Venezuela.

Begomoviruses are one of the major groups of plant viruses with an important economic impact on crop production in tropical and subtropical regions. The global spread of its polyphagous vector, the whitefly Bemisia tabaci, has contributed to the emergence and diversification of species within this genus. In this study, we found a putative novel begomovirus infecting tomato plants in Venezuela without a cognate DNA-B component. This begomovirus was genetically characterized and compared with related species. Furthermore, its infectivity was demonstrated by agroinoculation of infectious clones in tomato (Solanum lycopersicum) and Nicotiana benthamiana plants. The name Tomato twisted leaf virus (ToTLV) is proposed. ToTLV showed the typical genome organization of the DNA-A component of New World bipartite begomoviruses. However, the single DNA component of ToTLV was able to develop systemic infection in tomato and N. benthamiana plants, suggesting a monopartite nature of its genome. Interestingly, an additional open reading frame ORF was observed in ToTLV encompassing the intergenic region and the coat protein gene, which is not present in other closely related begomoviruses. A putative transcript from this region was amplified by strand-specific reverse transcription-PCR. Along with recent studies, our results showed that the diversity of monopartite begomoviruses from the New World is greater than previously thought.

Characterization of Non-coding DNA Satellites Associated with Sweepoviruses (Genus Begomovirus, Geminiviridae) - Definition of a Distinct Class of Begomovirus-Associated Satellites.

Begomoviruses (family Geminiviridae) are whitefly-transmitted, plant-infecting single-stranded DNA viruses that cause crop losses throughout the warmer parts of the World. Sweepoviruses are a phylogenetically distinct group of begomoviruses that infect plants of the family Convolvulaceae, including sweet potato (Ipomoea batatas). Two classes of subviral molecules are often associated with begomoviruses, particularly in the Old World; the betasatellites and the alphasatellites. An analysis of sweet potato and Ipomoea indica samples from Spain and Merremia dissecta samples from Venezuela identified small non-coding subviral molecules in association with several distinct sweepoviruses. The sequences of 18 clones were obtained and found to be structurally similar to tomato leaf curl virus-satellite (ToLCV-sat, the first DNA satellite identified in association with a begomovirus), with a region with significant sequence identity to the conserved region of betasatellites, an A-rich sequence, a predicted stem-loop structure containing the nonanucleotide TAATATTAC, and a second predicted stem-loop. These sweepovirus-associated satellites join an increasing number of ToLCV-sat-like non-coding satellites identified recently. Although sharing some features with betasatellites, evidence is provided to suggest that the ToLCV-sat-like satellites are distinct from betasatellites and should be considered a separate class of satellites, for which the collective name deltasatellites is proposed.

[Transmission of tomato Venezuela virus by Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), in Maracaibo, Venezuela]. / Transmisión del tomato Venezuela virus por Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), en Maracaibo, Venezuela.

The biological transmission of Tomato Venezuela virus (ToVEV) by biotype B of the whitefly species Bemisia tabaci (Gennadius) increased (21.7-95.0%), and the time for symptom expression decreased (16-12.6 days) as the number of viruliferous whiteflies allowed access for inoculation to susceptible tomato plants increased from 1 to 20 adults/plant. When acquired only as a nymph, adults of this biotype transmitted the virus to 88.3% of susceptible tomato plants, using 15 viruliferous individuals per test plant, corroborating the circulative nature of the transmission. Disease incidence further increased (up to 100%) when the individuals were allowed to feed again on a virus-infected plant as adults. Leaf area, plant height and dry matter were significantly affected in ToVEV infected tomato plants.

Transmisión del tomato Venezuela virus por Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), en Maracaibo, Venezuela / Transmission of tomato Venezuela virus by Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), in Maracaibo, Venezuela

The biological transmission of Tomato Venezuela virus (ToVEV) by biotype B of the whitefly species Bemisia tabaci (Gennadius) increased (21.7-95.0 percent), and the time for symptom expression decreased (16-12.6 days) as the number of viruliferous whiteflies allowed access for inoculation to susceptible tomato plants increased from 1 to 20 adults/plant. When acquired only as a nymph, adults of this biotype transmitted the virus to 88.3 percent of susceptible tomato plants, using 15 viruliferous individuals per test plant, corroborating the circulative nature of the transmission. Disease incidence further increased (up to 100 percent) when the individuals were allowed to feed again on a virusinfected plant as adults. Leaf area, plant height and dry matter were significantly affected in ToVEV infected tomato plants.

Efecto de algunos insecticidas sobre la mota blanca del guayabo, Capulinia SP. (Hemiptera: Eriococcidae) / Effects of some insecticides on guava cottony scale, Capulinia SP. (Hemiptera: Eriococcidae)

Durante ene-mar 2004 y jun-jul 2005, dos ensayos fueron realizados para evaluar el efecto de algunos insecticidas sobre Capulinia sp. En el primero, realizado en el laboratorio, los tratamientos incluidos fueron clorpirifos (0,06 por ciento v/v i.a.), imidacloprid (0,06 por ciento p/v i.a.), azadirachtina (0,45 por ciento p/v i.a.), Bauveria bassiana (2x10¹² conidias/100g; 2,5g/l) y un testigo absoluto. A las mezclas de insecticidas les fue añadido un surfactante (Extravón 200 0,5 por ciento v/v). Para el segundo ensayo, realizado fuera del laboratorio, fue incluido un tratamiento adicional consistente en surfactante+agua solamente. Se contó el número de individuos vivos y muertos, previo a la aplicación de tratamientos y a las 48, 72, 96h postaplicaciones, seguido de seis y siete conteos semanales, para el primer y segundo ensayo, respectivamente. El porcentaje de mortalidad fue significativamente superior sobre plantas tratadas con clorpirifós y con imidacloprid, bajo los cuales todas las plantas llegaron al final de los ensayos en buenas condiciones, contrastando con los restantes tratamientos, donde hubo tallos necrosados debido al daño causado por el insecto. A pesar de la efectividad demostrada, el uso de estos dos insecticidas debe ser considerado dentro de la racionalidad del manejo integrado de plagas.