Incidência e progresso de begomovirose do tomateiro sob diferentes sistemas de manejo da mosca-branca em Florestal, MG

• Autor(a) principal: Malta, Antônio Wilson de Oliveira
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1029
• topic: Tomateiro; Geminiviridae; Begomovirus; Mosca-branca; Incidência; Progresso; Tomatoes; Geminiviridae; Begomovirus; Whitefly; Incidence; Progress; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::FITOSSANIDADE::FITOPATOLOGIA

The genus Begomovirus in the Geminiviridae family includes ssDNA viruses transmitted by the whitefly Bemisia tabaci (Homoptera: Aleyrodidae) to dicot hosts. After the introduction of the B biotype of B. tabaci in Brazil in the early 1990's, begomovirus epidemics became common in tomato crops throughout the country. However, incidence and progress of the disease is highly variable along successive growing seasons in different regions. The objectives of this work were to determine the viral species present in the field and to investigate the spatial and temporal dynamics of the disease under different whitefly management strategies, during 2006 and 2007, in the city of Florestal, Minas Gerais state. Treatments consisted on the combinations of three management strategies (conventional, organic and no management) and two F1 hybrids ('Carmen', susceptible to begomoviruses, and Thaty‟, carrying the Ty-1 gene and which is tolerant to the viruses present in the field in Brazil). The experiment was set up in a randomized block design with 6 replications, in a 3x2 factorial scheme. Ten target plants were mapped in each experimental unit. Whitefly populations were monitored on a weekly basis. A leaf disk was collected from each target plant every two weeks for DNA extraction and begomovirus detection and identification. Visual observations of symptomatic target plants were also registered. Five consecutive plantings were carried out from Jan 2006 until Jan 2008. Only in the fifth and last planting did whitefly populations and begomovirus incidence reach epidemic levels. The following begomoviruses were detected in tomato plants during the fifth planting: Sida micrantha x mosaic virus (SiMMV), Tomato chlorotic mottle virus (ToCMoV), Tomato rugose mosaic virus (ToRMV) and Tomato yellow spot virus (ToYSV). Moreover, Euphorbia yellow mosaic virus (EuMV) was detected in a sample of the ubiquitous weed Euphorbia heterophylla, and ToCMoV in a sample of Sida micrantha. Therefore, four distinct begomoviruses were found in tomatoes. ToCMoV was detected both in tomato and Sida micrantha, and EuMV was detected only in a weed. At the first evaluation (35 days after planting, dap), 73 plants were infected, but only 13 of those were showing symptoms. Disease incidence increased from 35 dap until 80 dap, and then decreased until 95 dap in all treatments, becoming stable until the last evaluation at 110 dap. No statistically significant effects were observed for whitefly management strategy or F1 hybrid, and it was not possible to fit the progress curves obtained into any epidemiological model. Likewise, analysis of the area under the disease progress curve for the different treatments did not indicate any significant effects of either management strategy or F1 hybrid. Based on these results, it is possible to conclude that: (i) the Florestal area has a great species diversity of begomoviruses in tomato; (ii) symptoms in the field are unreliable as indicators of begomovirus incidence and disease progress; (iii) disease progress studies should be carried out along with vector monitoring in the target host in assays with a preestablished spatial distribution; (iv) begomovirus epidemics in tomatoes have the potential to cause significant yield losses when peaking during the flowering stages of the crop, independently of whitefly management practices.