Tomato-infecting begomoviruses have been reported throughout Brazil since the introduction of the B biotype of Bemisia tabaci. Here, we report a large scale survey on the distribution and genetic diversity of tomato-infecting begomoviruses. Tomato samples with typical begomovirus symptoms were collected in seven different states, comprising the major tomato growing areas of the country. Viruses were detected by polymerase chain reaction (PCR) using universal primers for the genus Begomovirus. PCR-amplified fragments were cloned and sequenced. Based on sequence comparisons and phylogenetic analyses, at least seven previously undescribed species of begomoviruses were found. Four of the new viruses were found exclusively in the Southeastern states, two exclusively in the Northeastern states, and one was found in both regions. Sequence comparisons reveal strong evidence of recombination among the Brazilian begomoviruses. Together, the results indicate the existence of a high degree of pre-existing genetic diversity among tomato-infecting begomoviruses in Brazil and suggest that these viruses have emerged after being transferred from natural hosts to tomatoes, due to the introduction into Brazil of a novel polyfagous biotype of the whitefly vector.

The genetic diversity of begomovirus isolates from tomato (Lycopersicon esculentum) fields in the Southeastern region of Brazil was analyzed by direct sequencing of PCR fragments amplified by using universal oligonucleotides for the begomovirus DNA-A, and subsequent computer-aided phylogenetic analysis. Samples of tomato plants and associated weeds showing typical symptoms of virus infection were collected at seven locations in the states of Minas Gerais, Espírito Santo and Rio de Janeiro. A total of 137 out of 369 samples were infected with a begomovirus based on PCR analysis. Phylogenetic analysis indicated a high degree of genetic diversity among begomoviruses infecting tomatoes in the sampled area. One species (Tomato chlorotic mottle virus, TCMV) occurs predominantly in Minas Gerais, whereas in Rio de Janeiro and Espírito Santo a distinct species, not yet fully characterized, predominates. Phylogenetic analysis further indicates the presence of an additional four possible new species. This high degree of genetic diversity suggests a recent transfer of indigenous begomovirus from wild hosts into tomatoes. The close phylogenetic relationship verified between begomovirus infecting tomato and associated weeds favors this hypothesis.

Geminiviruses are characterized by a circular, single-stranded DNA genome and twinned icosahedral particles. Begomoviruses (whitefly-transmitted geminiviruses) are a major constraint to crop production worldwide. In Brazil, tomato-infecting begomoviruses emerged as serious pathogens over the last 10 years, due to the introduction of a new biotype of the insect vector. Tomato yellow spot virus (ToYSV) is a newly described begomovirus originally isolated from tomato, but phylogenetically closer to viruses from Sida sp. A study was performed to determine the viability of pseudorecombinants formed between the DNA components of ToYSV and other weed-and tomato-infecting begomoviruses from Brazil. Despite its closer relationship to weed-infecting viruses, ToYSV was only capable of forming viable pseudorecombinants with tomato viruses. An infectious pseudorecombinant formed between ToYSV DNA-A and tomato crinkle leaf yellows virus (TCrLYV) DNA-B induced severe symptoms in Nicotiana benthamiana. This was attributed, at least in part, to the fact that the origins of replication of both components had identical Rep-binding sequences. However, this was not the case for another infectious pseudorecombinant formed between tomato golden mosaic virus (TGMV) DNA-A and ToYSV DNA-B, which have different Rep-binding sequences. These results reinforce the notion that pseudorecombinant formation cannot be explained solely on the basis of phylogenetic relationships and conserved iteron sequences, and suggest that the TGMV Rep protein may be more versatile in terms of recognizing heterologous DNA components than that of ToYSV.

Citrus leprosis (CL) is a serious threat to the citrus industry, especially for sweet oranges. For a long time, Citrus spp. were considered the only susceptible hosts. However, other plant species were also found either experimentally or naturally to be susceptible to Citrus leprosis virus C (CiLV-C). To assess the experimental host range of CiLV-C, a large number of plant species were inoculated with Brevipalpus phoenicis, viruliferous to CiLV-C, under experimental conditions. Out of the 140 tested species (43 families), 59 species (24 families) developed localized chlorotic and/or necrotic lesions upon inoculation of leaves with viruliferous mites, and 40 species (18 families) of them yielded positive results for CiLV-C detection in at least one of the following assays: ELISA, RT-PCR, transmission electron microscopy and immunfluorescence. For those that developed lesions and yielded negative results in CiLV-C detection assays, the results may be attributed to the small number of lesions and their necrotic state with very little viral material. The fact that a considerable number of plant species are susceptible to the virus after mite inoculation brings up implications for the epidemiology, quarantine and evolution of the citrus leprosis pathosystem.

-The objective of this work was the biological and molecular characterization of a begomovirus detected in São Joaquim de Bicas, Minas Gerais, Brazil, named , by determining its host range, complete nucleotide sequence and phylogenetic relationships with other begomoviruses. Biological characterization consisted of a host range study using either sap inoculation or particle bombardment as inoculation methods. The yellow spot virus can infect plants in Solanaceae and Amaranthaceae, including economically importat crops as sweet pepper, and weeds as Datura stramonium and Nicotiana silvestris. For the molecular characterization, the fulllength genome (DNA-A and DNA-B) was amplified, cloned and completely sequenced. Sequence comparisons and phylogenetic analyses indicated that TGV-[Bi2] constitutes a novel begomovirus species named Tomato yellow spot virus (ToYSV), closely related to Sida mottle virus (SiMoV).Index terms: Lycopersicon esculentum, Bemisia tabaci, ToYSV, molecular biology, geminivirus, whitefly. Caracterização do Tomato yellow spot virus, um novo begomovírus isolado de tomateiro no Brasil