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Data inicial: 1998Data final: 1998Tem arquivos: SimAssunto: search.filters.subject.A new disease

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    Bacterial blight (Xanthomonas campestris) of suflower (Helianthus annuus), a new disease
    (Revista Ceres, 1998-05) Romeiro, Reginaldo da Silva; Moura, Andréa Bittencourt
    In Vicosa, Minas Gerais, Brazil, a disease in sunflower (Helianthus annuus) was observed, whose symptoms show up as necrotic lesions, always surrounded by chlorotic haloes, predominately located at the leaf margin and, less frequently, dispersed in the leaf limb. The same lesion patterns were also visualized in stem and flower parts. Lesion fragments mounted in water and observed under the lowest microscope magnification showed cepious bacterial streams indicating a bacterial etiology for the disease. From lesions a bacterium was isolated that produces yellow, shining, regular edges, elevated colonies in standard culture media, able to induce HR in bean leaves and to reproduce original symptoms if inoculated in the host. Isolates are straight, regular, rod-shaped cells, Gram-negative, unable to use asparagine a sole Carbon and/or Nitrogen source, strict aerobes, xanhomonadines producers, are not tumorogenic and can be positioned in the genus Xanthomonas. Biological, biochemical and staining tests lead to the identification of the pathogen as Xanthomonas campestris. Its is not known the way by which the pathogen was introduced in the region but it might be through botanical seeds, Losses to the pathogen are very severe in spite of that fact that plant death was not observed or suppression of flower production. A preposition for creation of a new pathovar "Silvia", being, as a consequence, the name of the pathogen Xanthomonas campestris pv. silvia has been made.