Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item First record of Cercospora pistiae causing leaf spot of water lettuce ( Pistia stratioites ) in Brazil, with particular reference to weed biocontrol(Mycopathologia, 1998-11) Barreto, R. W.; Evans, H. C.; Hanada, R. E.Pistia stratioites , the water lettuce, is an important pantropical aquatic weed. It has been the target of successful classical biocontrol programmes utilizing an insect natural enemy collected in Brazil and introduced into Australia, Papua New Guinea and South Africa. Little attention was given to the fungal pathogens associated with this weed as potential biocontrol agents. An 11-month field survey in the state of Rio de Janeiro involving repeated visits to 12 sites, and a 2-month survey in the Amazonas Basin (Amazonas state) in Brazil, yielded only one pathogenic fungus on P. stratioites. This was identified as Cercospora pistiae. No previous record of this species has been made in Brazil nor in the New World. The fungus is described and its taxonomy and biocontrol potential discussed herein. C. pistiae is a damaging pathogen of water lettuce. Its distribution was restricted to two interconnected sites in Rio de Janeiro. A literature and herbaria survey yielded few fungi associated to water lettuce (8 species), probably reflecting a lack of adequate collection in the centre of origin of the plant.Item Resistência de cultivares e linhagens de feijão-vagem à antrocnose, mancha-angular e ferrugem(Revista Ceres, 1998-03) Silva, Marcelo B. da; Paula Jr., Trazilbo J.; Pinto, Cleide M. Ferriera; Niestche, Silvia; Carvalho, Geraldo A. de; Faleiro, Fábio G.Objetivou-se, neste trabalho, verificar a resistência de alguns cultivares e linhagens de feijão-vagem do programa de melhoramento da EPAMIG/UFV , especialmente dos materiais de hábito de crescimento determinado, à antracnose, mancha-angular e ferrugem, por meio da inoculação artificial de importantes raças ou isolados dos respectivos agentes causadores dessas doenças. O cultivar Manteiga Maravilha foi resistente às raças 64, 65, 69, 73 e 87 de Colletotrichum lindemuthianum. O Novirex foi resistente às raças 64, 65, 69 e 87, e o Argus às raças 69 e 81. Os demais materiais foram suscetíveis a praticamente todas as raças inoculadas. Nenhum cultivar ou linhagem foi resistente à raça 89 de Colletotrichum lindemuthianum, que ocorre frequentemente em Minas Gerais. O cultivar Manteiga Maravilha também foi resistente às raças 31.21, 31.23, 59.39 e 63.55 de Phaeoisariopsis griseola. Os cultivares Macarrão Preferido e Novirex foram resistentes às raças 31.21, 59.39 e 63.55. Os demais materiais foram suscetíveis a pelo menos quatro das raças inoculadas. Todos os cultivares e linhagens foram suscetíveis à raça 63.23 de P. griseola, uma das mais frequentes em Minas Gerais. O cultivar Macarrão Favorito foi imune aos isolados Ua-l e Ua-4 de Uromyces appendiculatus e suscetível aos demais. Mimoso Rasteiro, por sua vez, foi resistente ao isolado Ua-3 e moderadamente resistente aos outros isolados. Os materiais de hábito de crescimento determinado que se destacaram foram Mimoso Rasteiro, no ensaio com ferrugem, Novirex, nos ensaios com antracnose e mancha-angular, e Argus, no ensaio com antracnose.Item Bacterial blight (Xanthomonas campestris) of suflower (Helianthus annuus), a new disease(Revista Ceres, 1998-05) Romeiro, Reginaldo da Silva; Moura, Andréa BittencourtIn 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.Item Ergosterol accumulation and oil quality changes in stored soybean invaded by Aspergillus ruber (A. glaucus group)(Mycopathologia, 1998-11-03) Dhingra, Onkar D.; Jham, Gulab; Napoleão, Ivani T.Soybean seed samples inoculated with spores of Aspergillus ruber were stored for 20 to 140 days at 25 ± 1 °C with moisture content varying from 11.3% to 17.7%. Seeds were colonised by the fungus within 20 days at all moisture levels. Ergosterol concentration in seeds increased with time of storage, being slow in samples with moisture content of 11.3% to 13.1% and more rapidly in those with higher moisture content. Free fatty acid (FFA) content also increased following the pattern of ergosterol. Equations were used to predict minimum safe storage period of the seeds at 25 °C. The rise in FFA is due to increase of A. ruber mass within the seed. Fungal growth did not affect fatty acids profiles or iodine index of the extracted oil. The results suggest revision of the present recommendations regarding seed moisture during storage. The FFA concentration of a seed lot can be used as a sensitive indicator of seed deterioration due to storage fungi.