Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Influência de semeaduras sucessivas de feijoeiro na severidade da mancha-angular e ferrugem e perdas na produção(Pesquisa Agropecuária Brasileira, 1999-08) Rodrigues, Fabrício de Ávila; Fernandes, Jonas Jäger; Martins, MaurícioA mancha-angular (Phaeoisariopsis griseola) e a ferrugem (Uromyces appendiculatus) são algumas das mais prejudiciais doenças do feijoeiro na região do Triângulo Mineiro, Minas Gerais. O objetivo deste estudo foi determinar a influência das semeaduras sucessivas na severidade da mancha-angular e da ferrugem, bem como as perdas na produção em decorrência dessas doenças. Os experimentos foram conduzidos em condições de campo, nas safras outono-inverno (1994) e das águas (1994/95), cada uma com três semeaduras sucessivas de feijão. A severidade da mancha-angular e da ferrugem aumentou significativamente da primeira para a terceira semeadura, atingindo nível mais elevado na última. As semeaduras anteriores foram a fonte de inóculo para os cultivos subseqüentes. Aplicações de fungicida foram eficientes no controle das doenças, permitindo um aumento significativo da produção de grãos, quando comparado com o controle. A mancha-angular apresentou maior incidência no outono-inverno e nas águas, e a ferrugem, apenas no outono-inverno. Nessas safras as condições climáticas (temperatura e umidade relativa) favoreceram a evolução das doenças, resultando num aumento da severidade. Houve uma correlação negativa e altamente significativa entre a severidade da mancha-angular e da ferrugem com a produção de grãos nas duas safras.Item Efeito do silicato de cálcio e da autoclavagem na supressividade e na conducividade de dois solos à Rhizoctonia solani(Pesquisa Agropecuária Brasileira, 1999-08) Corrêa, Gilberto Fernandes; Korndörfer, Gaspar Henrique; Santos, Maria Amelia dos; Datnoff, Lawrence Elliot; Rodrigues, Fabrício de ÁvilaObjetivou-se verificar o efeito da aplicação de silicato de cálcio e da esterilização na supressividade natural de um Latossolo Vermelho-Escuro (LEa) álico textura muito argilosa e na conducividade natural de uma Terra Roxa Estruturada eutrófica (TRe) ao fungo Rhizoctonia solani, em condições de casa de vegetação. Utilizou-se o delineamento inteiramente casualizado em esquema fatorial 2 x 3 x 2. Os fatores foram: duas classes de solo (LEa e TRe - 0-20 cm); três tratamentos (esterilização ou não por autoclavagem, aplicação de silicato e testemunha) e infestação ou não com R. solani, com três repetições e 16 plântulas de feijoeiro por parcela. A aplicação de silicato foi feita incorporando 0,63 g do produto em 1 kg de cada material de solo, seguido de incubação por 30 dias. Para promover a infestação artificial, foram colocados 800 mg de inóculo em 1 kg de cada material de solo. O silicato de cálcio aumentou os teores de Ca trocável e a soma de bases nos dois solos. Um decréscimo na saturação por Al de 70 para 19% e um aumento na saturação por bases de 9 para 21% alteraram significativamente a supressividade natural do LEa à R. solani. Com relação à TRe, a aplicação de silicato não teve nenhum efeito na sua conducividade, dado ao seu natural caráter eutrófico, o qual já é favorável ao desenvolvimento deste fungo. A esterilização não influiu no desenvolvimento de R. solani, o que sugere que os fatores abióticos foram os responsáveis pela supressividade ou conducividade desses solos.Item A new species of Diorchidiella with a spermogonial state(Mycological Research, 1995-07) Ferreira, F. A.; Carvalho, A. O.Diorchidiella verlandii sp. nov. on Mimosa schomburqkii is described as the second species of Diorchidiella. It has spermogonia of type 5 and at least one beaked cell on its bicellulur teliospores. This is the first report of a spermogonial state in Diorchidiella.Item The mycobiota of the weed Lantana camara in Brazil, with particular reference to biological control(Mycological Research, 1995-07) Barreto, Robert W.; Evans, Harry C.; Ellison, Carol A.A survey of the fungi associated with the tropical weed Lantana camara was conducted during 1988 and 1989 in part of its native range in southern Brazil. The sampling activity was concentrated mainly in the state of Rio de Janeiro, covering 70 sites located in different climatic or ecological zones. The survey continued and was extended to the Amazon and northeast regions. Nine fungal species were identified as members of the mycobiota, including the previously undescribed fungi: Ceratobasidium lantanae-camarae sp. nov., Dendryphiella aspera sp. nov. and Micropustulomyces mucilaginosus gen. et sp. nov. Perisporiopsis lantanae, which has not been recorded previously in Brazil, has its anamorph described for the first time. The rusts Aecidium lantanae were also recorded. Field observations suggest that several fungal pathogens have potential as classical biocontrol agents of the weed in the Old World tropics: Ceratobasidium lantanae-camarae and Puccinia lantanae in lowland humid climates; Mycovellosiella lantanae, Prospodium tuberculatum and Micropustulomyces mucilaginosus in more elevated or subtropical areas. In addition, databases and herbaria were consulted in order to compile a world list of fungal pathogens associated with L. camara.Item The mycobiota of the weed Mikania micrantha in southern Brazil with particular reference to fungal pathogens for biological control(Mycological Research, 1995-03) Barreto, Robert Weingart; Evans, Harry CharlesA survey of the fungi associated with the tropical weed Mikania micrantha was conducted during 1988 and 1989 in part of its native range in southern Brazil. Sampling was concentrated mainly in the state of Rio de Janeiro, covering 70 sites in different climatic or ecological zones. Nine species were identified, including the recently described downy mildew species Basidiophora montana and the previously undescribed Mycosphaerella mikania-micranthae sp. nov. with its anamorph Septoria mikania-micranthae. Asperisporium mikaniae comb. nov., Asperisporium mikaniigena comb. nov., Pseudocercospora plunketii comb. nov., and Cercospora mikaniacola are new records for Brazil. Field observations indicate that Basidiophora montana has potential as a classical biological control agent of the weed in Old World subtropical or montane climates, whilst Mycosphaerella mikania-micranthae and the microcyclic rust Puccinia spegazzinii appear to be equally damaging to the host but to have a wider climatic range and thus are highly promising agents for introduction throughout the Palaeotropics.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 Fungal pathogens of Calotropis procera (rubber bush), with two new records from Brazil(Australasian Plant Pathology, 1999-06) Barreto, Robert W.; Pomella, Alan W. V.; Evans, Harry C.Fungal pathogens associated with the asclepiadaceous weed Calotropis procera (rubber bush) are documented from published, as well as unpublished sources. Two new host-pathogen associations from Brazil; Phaeoramularia calotropidis and Puccinia obliqua, are recorded. The latter species infects the host systemically and induces the formation of conspicuous and damaging witches’ brooms. The rust appears to exert some control of C. procera in the more humid areas of Brazil and the biocontrol potential of this and the other listed pathogens is discussed.Item Mycobiota of the weed Cyperus rotundus in the state of Rio de Janeiro, with an elucidation of its associated Puccinia complex(Mycological Research, 1995-04) Barreto, R. W.; Evans, H. C.A survey of the fungi associated with the pantropical weed Cyperus rotundus was conducted during 1988 and 1989 in part of its exotic range in southern Brazil. The sampling activity was concentrated in the state of Rio de Janeiro, covering 70 sites located in different climatic or ecological zones. Five species were identified as members of the pathogenic mycobiota: Cercospora caricis, Cintractia limitata, Dactylaria higginsii, Duosporium cyperi and Puccinia canaliculata. All are reported here for the first time in Brazil and Duosporium cyperi is a new record from Cyperus rotundus. The complex of six rust species belonging to Puccinia which have been described from C. rotundus was critically re-examined and three of these, Puccinia conclusa, P. cypericola and P. philippinensis are considered to be synonyms of P. canaliculata. The implications for biological control of C. rotundus are discussed.Item Nimbya alternantherae and Cercospora alternantherae: two new records of fungal pathogens on Alternanthera philoxeroides (alligatorweed) in Brazil(Australasian Plant Pathology, 1999-06) Barreto, Robert W.; Torres, André N. L.Alternanthera philoxeroides is an amphibious herbaceous weed (alligatorweed) of the Amaranthaceae, and is a native of South America. It has become a very aggressive invader in many regions of the world. A preliminary survey for fungal pathogens to be used as biocontrol agents for this weed of five Brazilian States yielded two species, Nimbya alternantherae and Cercospora alternantherae. This is the first report of these species from Brazil. The pathogenicity of these fungi was tested against plants from Brazilian and Australian biotypes of A. philoxevoides. N. alternantherae was shown to be very damaging and appears to have biocontrol potential.Item A new bacterial disease of tomato in Viçosa, Minas Gerais state(Revista Ceres, 1995-05) Oliveira, José Rogério de; Miguel, Dulândula Silva; Romeiro, Reginaldo da SilvaIn 1991 it was observed a new disease of tomato in commercial plantations at the region of Viçosa, Minas Gerais State, Brazil. The disease shows up as necrotic lesions in leaves, either irregularly round or along leaf borders, initially small and increasing in size with age. These lesions are usually surrounded by a chlorotic halo. Drop exsudate tests indicated a bacterial etiology for the disease. From such lesions, it was consistently isolated a bacterium that gives rise to clear, opaque, regular, elevated and shinning colonies. Inoculations tests rendered HR in leaves of coffee, tobacco, bean and passion fruit as well as typical disease symptoms in tomato leaves. The bacterium is a single, regular, straight, Gram-negative, strictly aerobic rod, unable to use asparagine as sole C and N source, unable to produ-ce xanthomonadins, does not induce hipertrOphic growth in the host, produces a blue fluorescent pigment, grows easily in routine culture media and was positioned in the genus Pseudomonas, fluorescent group. Biochemical, staining and biological tests indicate the pathogen belongs to the species Pseudomonas syríngae pv. tomato,