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 Population changes of Macrophomina phaseolina in amended soils(Transactions of the British Mycological Society, 1980-06) Santos Filho, Edgar; Dhingra, Onkar D.Population changes of Macrophomina phaseolina (Tassi) Goid. were followed in two soils amended with either wheat, corn, bean or alfalfa straw, or with nitrogen-enriched wheat straw or glucose and sodium nitrate at different C:N ratios. The population declined significantly initially in both soils with any amendment but later increased in soils amended with wheat or corn straw and in one soil amended with bean or alfalfa straw. Population declined with no subsequent increase when soil was amended with nitrogen-enriched wheat straw or glucose and sodium nitrate at C:N ratios equal to that of the natural plant residues. In general the population declined more rapidly when soil was amended with nitrogen-enriched wheat straw or glucose and nitrogen than if amended with either corn, bean or alfalfa straw and when soil was amended with low C:N ratios.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 Effect of soil temperature, moisture, and nitrogen on competitive saprophytic ability of Macrophomina phaseolina Author links open overlay panel(Transactions of the British Mycological Society, 1981) Dhingra, Onkar D.; Chagas, DaniloThe effect of soil temperature, moisture and nitrogen on saprophytic colonization of bean or wheat stems by Macrophomina phaseolina was studied in two soils. Maximum colonization of the substrate units occurred at 15–20° and decreased with increasing soil temperature. At 15° more wheat than bean stems were colonized whereas at higher temperatures the reverse occurred. Maximum colonization of substrates occurred at 15–25% of moistureholding capacity, and percentage colonization decreased with increasing soil moisture. Addition of nitrogen to soil completely inhibited saprophytic colonization.Item Effect of herbicides on competitive saprophytic colonization by Macrophomina phaseolina of soybean stems(Transactions of the British Mycological Society, 1982-10) Dhingra, O. D.; Cerkauskas, R. F.; Sinclair, J. B.The effect of paraquat, glyphosate and sodium chlorate : sodium borate (50:50), applied at commercial rates was tested on the competitive saprophytic colonization by Macrophomina phaseolina of greenhouse and field grown soybean stems at three different growth stages in two soils. A significant difference in colonization was recorded between herbicide treatments and controls in soil with a high organic content but no significant difference in colonization was found between herbicides. The highest levels of stem colonization occurred 10 days after incubation in soil. Colonization in treated and untreated stems progressively declined at similar rates for all growth stages and in both soil types. In both soils, field stems had greater levels of colonization when sampling time and herbicide factors were excluded. The nonpersistence of M. phaseolina in stems in soil suggests that the saprophytic activity of the fungus does not effectively increase its inoculum density in soil.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.
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