Academic literature on the topic 'Geminivirus. eng'

Whitefly-transmitted geminiviruses are a major constraint on tomato production in Mexico (3). In the Yucatan State, these viruses can cause serious losses in late season plantings. As part of an effort to characterize these viruses, leaf samples from four tomato plants showing symptoms of geminivirus infection, such as stunted growth and leaf mottling and deformation, were collected from a single field in the Yucatan State in February, 1996. Geminivirus nucleic acids were detected in leaf samples from all four plants by squash blot hybridization analysis with a general DNA probe for Western Hemisphere whitefly-transmitted geminiviruses (2). Nicotiana benthamiana plants inoculated with sap prepared with leaf tissue from one plant developed stunted growth and leaf mottling and deformation. When graft-transmitted from N. benthamiana to tomato, the geminivirus(es) induced leaf mottling and deformation, which were similar to symptoms in the field-collected tomato plants. The presence of geminivirus DNA in the sap- and graft-inoculated plants was confirmed with the polymerase chain reaction (PCR) and degenerate primers for the DNA-A (PAL1v1978 and PAR1c496) or DNA-B (PBL1v2040 and PCRc1) components of whitefly-transmitted geminiviruses (4). Using PCR and these degenerate primers, approximately 1.1-kb DNA-A and approximately 0.6-kb DNA-B fragments were amplified from DNA extracts prepared from leaves of each of the four Yucatan tomato plants. No DNA fragments were amplified from these extracts with primers for pepper huasteco geminivirus (pAL1c2329 and pAL1v1471, or pBR1c840 and pBL1v1830). To determine the identity of the geminivirus(es) infecting these tomato plants, the PCR-amplified DNA-A and DNA-B fragments from one of the samples were cloned and sequenced. Comparisons made with these sequences revealed two distinct types of DNA-A and DNA-B clones, indicating a mixed infection of at least two bipartite geminiviruses. DNA-A and DNA-B sequences of one set of clones were >97% identical to sequences of tomato mottle geminivirus (ToMoV) from Florida (1). The presence of ToMoV in all four tomato leaf samples was demonstrated by the PCR-mediated amplification of a 0.9-kb DNA-A fragment with ToMoV-specific primers (pAL1v2295 and pAR1c580). The identity of this 0.9-kb DNA fragment was further confirmed based upon its hybridization with a full-length clone of ToMoV DNA-A under high stringency conditions (2). A data base search made with the sequence of the other type of DNA-A clone revealed sequence identities of <70% with various bipartite geminiviruses (e.g., identities of 70% with tomato mottle, 69% with Sida golden mosaic, 67% with bean dwarf mosaic, and 66% with taino tomato mottle and with potato yellow mosaic), which confirmed that a second geminivirus was present in a mixed infection with ToMoV in this tomato leaf sample. To confirm the bipartite nature of this geminivirus, a DNA-B fragment that contained the common region (CR) sequence was amplified from the same sample with PCR and primers PBL1v2040 and PBR1c970 (a degenerate primer that anneals within the BV1 open reading frame; F. M. Zerbini and R. L. Gil-bertson, unpublished data), cloned, and sequenced. The CR sequence of this DNA-B fragment was 96% identical to that of the DNA-A fragment, which establishes the presence of another bipartite geminivirus in this sample. This is the first report of ToMoV in Mexico. These results also suggest that at least two bipartite geminiviruses may infect tomatoes in the Yucatan Peninsula. References: (1) A. M. Abouzid et al. J. Gen. Virol. 73:3225, 1992. (2) R. L. Gilbertson et al. Plant Dis. 75:336, 1991. (3) J. E. Polston and P. K. Anderson. Plant Dis. 81:1358, 1997. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.

Rhynchosia minima was suspected to be a weed host of Bean golden yellow mosaic virus (BGYMV, previously designated Bean golden mosaic virus type II). Leaf tissue that exhibited yellow mosaic foliar symptoms characteristic of a geminivirus infection was collected in the Comayagua Valley in Honduras in July 1999. Extraction of viral DNA from the symptomatic leaves was accomplished with the DNeasy Plant Mini Kit (Qiagen Inc., Valencia, CA). Subsequent viral DNA amplification was accomplished with degenerative primers for the cp gene (AV494/AC1048) (4). The 570-bp fragment was cloned into the pGEM T-Easy vector (Promega Corp., Madison, WI) producing the recombinant plasmid pRhyb5. The viral insert was sequenced, and from this sequence, specific primers (RHc549 and RHv29) were designed to amplify the remaining part of DNA-A. The 2.1-kb-amplified polymerase chain reaction (PCR) fragment was cloned into the pGEM T-Easy vector producing the recombinant plasmid (pRhya-sp), and the viral insert was sequenced. Nucleotide sequence comparison (GAP program, Wisconsin Package Version 10.0, Genetics Computer Group, Madison, WI) of the complete 2,624-bp DNA-A (GenBank accession no. AF239671) to geminiviruses representing the major phylogenetic clusters (1) showed nucleotide identities ranging from 63 to 82%. Sequence comparisons for the common region and rep, trap, ren, and cp genes with the most closely related geminivirus, Pepper hausteco virus (PHV, X70418), gave 76, 82, 79, 81, and 82% nucleotide identities, respectively. There is a direct repeat (TATCGGT) of 7 nt 5′ (viral sense polarity) of the conserved TATA box, and this repeat is most analogous to that in PHV (1). Specific primers were designed in the complementary sense (RGBc2414, BGBc2553) from the common region DNA-A sequence and used with a degenerative viral sense primer for the DNA-B (PBC1v2039) (3) to amplify a 647-bp fragment. Sequence comparison for the common region (134 nt from the rep gene start codon toward the 3′ end) from the DNA-B sequence had 88% nt identity to the DNA-A sequence, thus indicating that this geminivirus is bipartite. These sequence analyses indicated that this geminivirus isolated from R. minima is distinct from previously described geminiviruses, and we propose the name Rhynchosia golden mosaic virus (RGMV). From rep gene sequence alignments, RGMV has an apparent genome recombination between Old and New World geminiviruses (Tomato yellow leaf curl virus and Bean dwarf mosaic virus) as previously noted for PHV (2). Our results indicate that RGMV is a distinct geminivirus from BGYMV, and, thus, additional studies are needed to establish the importance of R. minima as a reservoir for vegetable-infecting geminiviruses. This study is the first report of another virus in the PHV phylogenetic cluster and is thus of importance in the understanding of recombinant viruses and their phylogenetic relationship to other characterized geminiviruses. References: (1) J. C. Faria et al. Phytopathology 84:321, 1994. (2) M. Padidam et al. Virology 265:218, 1999. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993. (4) S. Wyatt and J. K. Brown. Phytopathology 86:1288, 1996.

Although tomato golden mosaic virus (TGMV) was reported in Brazil more than 20 years ago (3), tomato-infecting geminiviruses have not been of economic significance in the country until recently. However, a sharp increase in the incidence of geminivirus-like symptoms in tomatoes has been reported in several areas of Brazil since 1994. This has coincided with the appearance of the B biotype of Bemisia tabaci, which, as opposed to the A biotype, readily colonizes solanaceous plants (2). We have isolated geminiviruses from symptomatic tomato plants in the Federal District, in two different areas of the state of Minas Gerais, and in the state of Pernambuco. Tomato plants in these areas showed a variety of symptoms, including yellow mosaic, severe leaf distortion, down-cupping, and epinasty. Whitefly infestation was high in all fields sampled, and in some fields, particularly in Pernambuco, incidence of virus-like symptoms was close to 100%, and no tomatoes of commercial value were harvested (1). Using primer pairs PAL1v1978/PAR1c496 and PCRc1/PBL1v2040 (4), DNA-A and -B fragments were polymerase chain reaction (PCR)-amplified from total DNA extracted from diseased plants, cloned, and sequenced. Sequence comparisons of the PCR fragments indicated the existence of at least six different geminiviruses. The nucleotide sequence homologies for DNA-A fragments ranged from 67 to 80% for the 5′ end of the cp gene, and from 44 to 80% for the 5′ end of the rep gene. Data base comparisons indicated the viruses are most closely related to TGMV, bean golden mosaic virus from Brazil (BGMV-Br), and tomato yellow vein streak virus (ToYVSV), although homologies were less than 80% for the fragments compared. A similar lack of a close relationship with each other and other geminiviruses was obtained with two DNA-B component PCR products compared, corresponding to the 5′ end of the BC1 open reading frame. Infectious, full-length genomic clones from the tomato viruses are being generated for biological and molecular characterization. References: (1) I. C. Bezerra et al. Fitopatol. Bras. 22:331, 1997. (2) F. H. França et al., Ann. Soc. Entomol. Bras. 25:369, 1996. (3) J. C. Matyis et al. Summa Phytopathol. 1:267, 1975. (4) M. R. Rojas et al. Plant Dis. 77:340, 1993.

Management of geminiviruses is a worldwide challenge because of the widespread distribution of economically important diseases caused by these viruses. Regardless of the type of agriculture, management is most effective with an integrated pest management (IPM) approach that involves measures before, during, and after the growing season. This includes starting with resistant cultivars and virus- and vector-free transplants and propagative plants. For high value vegetables, protected culture (e.g., greenhouses and screenhouses) allows for effective management but is limited owing to high cost. Protection of young plants in open fields is provided by row covers, but other measures are typically required. Measures that are used for crops in open fields include roguing infected plants and insect vector management. Application of insecticide to manage vectors (whiteflies and leafhoppers) is the most widely used measure but can cause undesirable environmental and human health issues. For annual crops, these measures can be more effective when combined with host-free periods of two to three months. Finally, given the great diversity of the viruses, their insect vectors, and the crops affected, IPM approaches need to be based on the biology and ecology of the virus and vector and the crop production system. Here, we present the general measures that can be used in an IPM program for geminivirus diseases, specific case studies, and future challenges.

Geminiviruses are probably the most important viral pathogen affecting tomatoes and other crops in the Caribbean region. In addition to losses previously caused by native virus populations, the introduction of tomato yellow leaf curl virus (TYLCV) into the area has become a major concern for tomato growers (1). Since the detection of TYLCV in Cuba, and later in Florida (2,3), we have been monitoring the tomato- and pepper-growing areas of the Yucatán Peninsula, México, for TYLCV. We also have reanalyzed samples previously collected. Other geminiviruses (pepper huasteco virus [PHV], Texas pepper virus [TPV], and tomato mottle virus [ToMoV]) in the area can cause symptoms similar to those induced by TYLCV, which led us to refine our analysis of samples, using a polymerase chain reaction (PCR) procedure that can differentiate between monopartite and bipartite begomoviruses based on the size of the amplification product, 750 and 600 bp, respectively. One advantage of using this set of primers is that the PCR product, which includes the amino terminus of the Rep protein, intergenic region, precoat protein, and amino terminus of the coat protein, can be sequenced completely with only one sequencing reaction from each end. Using the primer set, we analyzed samples collected from tomato and pepper fields (as well as from weeds surrounding the fields) from December 1996 until March 1999. In most cases, samples were taken from plants that showed yellowing, curling, and stunting symptoms. Most of the samples that were positive for geminiviruses came from plants infected with PHV or TPV. However, three tomato samples collected during two seasons in Dzidzantun and Yobain counties (northeast of Mérida, Yucatan) produced the larger PCR amplification product (750 bp) expected for monopartite begomoviruses. PCR products were cloned and sequenced to confirm their identity. The sequence was deposited in the GenBank Database (Accession no. AF168709) and compared with all geminivirus sequences deposited in the database. Analysis showed that the amplified fragment from the TYLCV strain present in the Yucatán is 99% identical to the isolate reported in the Dominican Republic and later found in Cuba (2). As previously noted, the isolate is almost identical to TYLCV-Isr (2). In addition to the PCR product, a full-length TYLCV clone was obtained directly from DNA extracts of an infected tomato plant. Further characterization of the full-length clone is underway. The fact that TYLCV was detected in two counties and in samples collected during two seasons confirms the presence of TYLCV in the Yucatán. Interestingly, although the first positive sample for TYLCV was collected during the winter of 1996 and 1997, current incidence is rather low—only two other positive samples have been detected in more recently collected samples. Perhaps the characteristics of the agriculture system in the Yucatán (small, disperse plots) or the presence of other geminiviruses have contributed to a slow spread of the virus. More comprehensive surveys are required to confirm the actual distribution of the pathogen in the area. References: (1) J. E. Polston et al. Plant Dis. 81:1358, 1997. (2) J. E. Polston et al. Plant Dis. 83:984, 1999. (3) P. L. Ramos et al. Plant Dis. 80:1208, 1996.

ABSTRACT Since 1997 two distinct geminivirus species, Tomato yellow leaf curl Sardinia virus (TYLCSV) and Tomato yellow leaf curl virus (TYLCV), have caused a similar yellow leaf curl disease in tomato, coexisted in the fields of southern Spain, and very frequently doubly infected single plants. Tomatoes as well as experimental test plants (e.g., Nicotiana benthamiana) showed enhanced symptoms upon mixed infections under greenhouse conditions. Viral DNA accumulated to a similar extent in singly and doubly infected plants. In situ tissue hybridization showed TYLCSV and TYLCV DNAs to be confined to the phloem in both hosts, irrespective of whether they were inoculated individually or in combination. The number of infected nuclei in singly or doubly infected plants was determined by in situ hybridization of purified nuclei. The percentage of nuclei containing viral DNA (i.e., 1.4% in tomato or 6% in N. benthamiana) was the same in plants infected with either TYLCSV, TYLCV, or both. In situ hybridization of doubly infected plants, with probes that discriminate between both DNAs, revealed that at least one-fifth of infected nuclei harbored DNAs from both virus species. Such a high number of coinfected nuclei may explain why recombination between different geminivirus DNAs occurs frequently. The impact of these findings for epidemiology and for resistance breeding concerning tomato yellow leaf curl diseases is discussed.

Tomato yellow leaf curl virus (TYLCV, formerly TYLCV-Is) and Tomato yellow leaf curl Sardinia virus (TYLCSV, formerly TYLCV-Sar) are geminivirus species of the genus Begomovirus that cause the disease known as tomato yellow leaf curl. In Spain, TYLCV and TYLCSV have coexisted in field and greenhouse tomato (Lycopersicon esculentum) crops since 1996 (2). TYLCV is also the causal agent of the leaf crumple disease of common bean (Phaseolus vulgaris) (1), a species that TYLCSV is unable to infect (2). Analysis of field samples from common bean plants affected by leaf crumple disease collected in Almería (southeastern Spain) during 1999 showed that, unexpectedly, several samples hybridized with TYLCV- and TYLCSV-specific probes prepared to the intergenic region (IR) as previously described (1). Polymerase chain reactions (PCR) performed with total nucleic acids extracted from one of these samples (ES421/99) using primer pairs specific to the IR of TYLCV (MA-30/MA-31) or TYLCSV (MA-14/MA-15) (1) gave no amplification product. However, the combination of MA-30 (5′ end of TYLCV IR) and MA-15 (3′ end of TYLCSV IR) produced a PCR DNA product of the expected size (351 bp). Direct DNA sequencing of this product (GenBank Accession No. AF401478) indicated the presence of a chimeric IR in ES421/99. Comparison of the obtained sequence with those available for isolates reported from Spain showed that the 5′ side (149 nt) from the stem-loop structure conserved in the IR of all geminiviruses was 99% identical to the corresponding region of TYLCV (GenBank Accession No. AF071228) and only 62% identical to TYLCSV (GenBank Accession No. Z25751). In contrast, the 3′ side (124 nt) from the stem-loop was 98% identical to the corresponding region of TYLCSV and only 57% identical to TYLCV. The 33-nt region involved in the stem-loop was 100% identical to TYLCV and showed one nucleotide change in the loop with respect to TYLCSV. Therefore, this DNA sequence data showed evidence of the occurrence in ES421/99 of a natural recombination between TYLCV and TYLCSV. The biological and epidemiological consequences of the presence of this new interspecific recombinant have yet to be determined. References: (1) J. Navas-Castillo et al. Plant Dis. 83:29, 1999. (2) S. Sánchez-Campos et al. Phytopathology 89:1038, 1999.

The amount of tomato yellow leaf curl geminivirus (TYLCV) DNA that accumulated in the vector Bemisia tabaci was studied by quantitative chemiluminescent dot-blot assay, using digoxigenin-labeled specific DNA probes. Large groups of female whiteflies were allowed to feed for 4, 12, 24, or 48 h on TYLCV-infected tomato plants and then were transferred to TYLCV-immune cucumber plants. Insects were sampled at different times during and after acquisition access and tested for TYLCV-DNA content. TYLCV-DNA assays were done either on whole insects oron the head plus prothorax (to include salivary glands) and abdomen separately. The maximum amount of TYLCV DNA, averaging from 0.5 to 1.6 ng per insect, was always attained at the end of the acquisition period. The mean amount then decreased by about 1 to 2% per day, remaining clearly detectable up to 20 days after the end of the acquisition period. Only some whiteflies that were TYLCV-positive in the abdomen were positive for head plus prothorax. In both parts of the body, TYLCV DNA remained detectable up to 18 days after the end of the acquisition period, showing that TYLCV DNA remains in insect tissues much longer than infectivity indicates.

ABSTRACTBoth posttranscriptional and transcriptional gene silencing (PTGS and TGS, respectively) participate in defense against the DNA-containing geminiviruses. As a countermeasure, members of the genusBegomovirus(e.g.,Cabbage leaf curl virus) encode an AL2 protein that is both a transcriptional activator and a silencing suppressor. The related L2 protein ofBeet curly top virus(genusCurtovirus) lacks transcription activation activity. Previous studies showed that both AL2 and L2 suppress silencing by a mechanism that correlates with adenosine kinase (ADK) inhibition, while AL2 in addition activates transcription of cellular genes that negatively regulate silencing pathways. The goal of this study was to clarify the general means by which these viral proteins inhibit various aspects of silencing. We confirmed that AL2 inhibits systemic silencing spread by a mechanism that requires transcription activation activity. Surprisingly, we also found that reversal of PTGS and TGS by ADK inactivation depended on whether experiments were conducted in vegetative or reproductiveNicotiana benthamianaplants (i.e., before or after the vegetative-to-reproductive transition). While AL2 was able to reverse silencing in both vegetative and reproductive plants, L2 and ADK inhibition were effective only in vegetative plants. This suggests that silencing maintenance mechanisms can change during development or in response to stress. Remarkably, we also observed that AL2 lacking its transcription activation domain could reverse TGS in reproductive plants, revealing a third, previously unsuspected AL2 suppression mechanism that depends on neither ADK inactivation nor transcription activation.IMPORTANCERNA silencing in plants is a multivalent antiviral defense, and viruses respond by elaborating multiple and sometimes multifunctional proteins that inhibit various aspects of silencing. The studies described here add an additional layer of complexity to this interplay. By examining geminivirus AL2 and L2 suppressor activities, we show that L2 is unable to suppress silencing inNicotiana benthamianaplants that have undergone the vegetative-to-reproductive transition. As L2 was previously shown to be effective in matureArabidopsisplants, these results illustrate that silencing mechanisms can change during development or in response to stress in ways that may be species specific. The AL2 and L2 proteins are known to share a suppression mechanism that correlates with the ability of both proteins to inhibit ADK, while AL2 in addition can inhibit silencing by transcriptionally activating cellular genes. Here, we also provide evidence for a third AL2 suppression mechanism that depends on neither transcription activation nor ADK inactivation. In addition to revealing the remarkable versatility of AL2, this work highlights the utility of viral suppressors as probes for the analysis of silencing pathways.

Resumo: Tomato severe rugose virus - ToSRV é um vírus pertencente ao gênero Begomovirus da família Geminiviridae, proveniemte de pimentão e transmitido pelo aleirodídeo Bemisia tabaci biótipo B. Este biótipo B foi introduzido no início dos anos 90, é um inseto polífago reproduzindo-se em mais de 500 espécies de plantas anuais e herbáceas. Causa danos diretos como a sucção de seiva com ação toxicogênica e aparecimento de fumagina, e danos indiretos pela transmissão de vírus, principalmente os begomovírus. O presente trabalho teve como objetivo estudar a interação do isolado ToSRV [PJU] com o vetor Bemisia tabaci biótipo B, avaliar a atratividade do inseto à diversos acessos de Capsicum spp., e determinar os biótipos de mosca-branca encontrados no Estado de São Paulo. Para avaliar a eficiência de transmissão do vírus pelo inseto foram realizadas as combinações tomateiro para tomateiro (T/T), tomateiro para pimentão (T/P), pimentão para pimentão (P/P) e pimentão para tomateiro (P/T). As melhores condições de transmissão foram observadas com temperaturas ao redor de 30 ºC, a partir de T/T e P/T. Quando diferentes números de insetos foram utilizados houve um aumento na transmissão, exceto para a combinação de P/P, onde não foi verificada esta correlação. Com relação ao período de acesso à aquisição, foi observado que maiores tempos de aquisição promoveram aumento na transmissão do vírus pela mosca-branca para T/T e P/T, enquanto que na combinação T/P e P/P, menores tempos de aquisição permitiram uma melhor transmissão.Utilizando-se um período de acesso à inoculação mínima de 15 minutos, foi possível a transmissão do vírus pelo inseto, exceto na combinação P/T e quanto maior este período, maior a taxa de transmissão. Não foi possível avaliar o período de latência, utilizando-se apenas um inseto e transferindo-o durante... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Tomato severe rugose virus - ToSRV is a virus belonging to the genus Begomovirus, family Geminiviridae, isolated from sweetpepper and transmitted by the aleyrodideo Bemisia tabaci biotype B. This new biotype B was introduced in the beginning of years 90 and it is an insect that multiplies in more than 500 species of annual and herbaceous plants. It toxicogenic action causes damages by suction the plants, the development of a fungus, fumagina, and these insects are vectors of different species of viruses, mainly begomovirus. The objective of this work, was to evaluate the interaction of the isolate ToSRV[PJU] with the vector Bemisia tabaci biotype B, to evaluate the attractiveness of the insect for the diverse genotypes of Capsicum spp, and to determine the biotype of whitefly in the State of São Paulo. To evaluate the efficiency of transmission of the virus by the insect different combinations were analyzed: tomato for tomato (T/T), tomato for sweetpepper (T/SP), sweetpepper for sweetpepper (SP/SP) and sweetpepper for tomato (SP/T). The best conditions of transmission were observed with temperatures around of 30 °C, from T/T and SP/T. Generally higher numbers of insects increased the transmission of the virus, but in the combination of SP/SP this was not observed. The acquisition access period was analysed and demonstrated that bigger times increased the transmission of the virus by the whitefly in the combinations T/T and SP/T. This was not observed in combination T/SP and SP/SP. The minimum period access of inoculation was of 15 minutes, except in combination SP/T. With one insect it wasn't possible to evaluate the period of latency of the virus. It was verified that the leaves of the apex and intermediary of 38 different Capsicum spp. genotypes are the most attractive places for the whitefly and have the h highest egg concentration. The most attractive access was Capsicum frutescens... (Complete abstract click electronic access below)
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Tomato severe rugose virus – ToSRV é um vírus pertencente ao gênero Begomovirus da família Geminiviridae, proveniemte de pimentão e transmitido pelo aleirodídeo Bemisia tabaci biótipo B. Este biótipo B foi introduzido no início dos anos 90, é um inseto polífago reproduzindo-se em mais de 500 espécies de plantas anuais e herbáceas. Causa danos diretos como a sucção de seiva com ação toxicogênica e aparecimento de fumagina, e danos indiretos pela transmissão de vírus, principalmente os begomovírus. O presente trabalho teve como objetivo estudar a interação do isolado ToSRV [PJU] com o vetor Bemisia tabaci biótipo B, avaliar a atratividade do inseto à diversos acessos de Capsicum spp., e determinar os biótipos de mosca-branca encontrados no Estado de São Paulo. Para avaliar a eficiência de transmissão do vírus pelo inseto foram realizadas as combinações tomateiro para tomateiro (T/T), tomateiro para pimentão (T/P), pimentão para pimentão (P/P) e pimentão para tomateiro (P/T). As melhores condições de transmissão foram observadas com temperaturas ao redor de 30 ºC, a partir de T/T e P/T. Quando diferentes números de insetos foram utilizados houve um aumento na transmissão, exceto para a combinação de P/P, onde não foi verificada esta correlação. Com relação ao período de acesso à aquisição, foi observado que maiores tempos de aquisição promoveram aumento na transmissão do vírus pela mosca-branca para T/T e P/T, enquanto que na combinação T/P e P/P, menores tempos de aquisição permitiram uma melhor transmissão.Utilizando-se um período de acesso à inoculação mínima de 15 minutos, foi possível a transmissão do vírus pelo inseto, exceto na combinação P/T e quanto maior este período, maior a taxa de transmissão. Não foi possível avaliar o período de latência, utilizando-se apenas um inseto e transferindo-o durante...
Tomato severe rugose virus - ToSRV is a virus belonging to the genus Begomovirus, family Geminiviridae, isolated from sweetpepper and transmitted by the aleyrodideo Bemisia tabaci biotype B. This new biotype B was introduced in the beginning of years 90 and it is an insect that multiplies in more than 500 species of annual and herbaceous plants. It toxicogenic action causes damages by suction the plants, the development of a fungus, fumagina, and these insects are vectors of different species of viruses, mainly begomovirus. The objective of this work, was to evaluate the interaction of the isolate ToSRV[PJU] with the vector Bemisia tabaci biotype B, to evaluate the attractiveness of the insect for the diverse genotypes of Capsicum spp, and to determine the biotype of whitefly in the State of São Paulo. To evaluate the efficiency of transmission of the virus by the insect different combinations were analyzed: tomato for tomato (T/T), tomato for sweetpepper (T/SP), sweetpepper for sweetpepper (SP/SP) and sweetpepper for tomato (SP/T). The best conditions of transmission were observed with temperatures around of 30 °C, from T/T and SP/T. Generally higher numbers of insects increased the transmission of the virus, but in the combination of SP/SP this was not observed. The acquisition access period was analysed and demonstrated that bigger times increased the transmission of the virus by the whitefly in the combinations T/T and SP/T. This was not observed in combination T/SP and SP/SP. The minimum period access of inoculation was of 15 minutes, except in combination SP/T. With one insect it wasn´t possible to evaluate the period of latency of the virus. It was verified that the leaves of the apex and intermediary of 38 different Capsicum spp. genotypes are the most attractive places for the whitefly and have the h highest egg concentration. The most attractive access was Capsicum frutescens... (Complete abstract click electronic access below)