Fitopatologia - Artigos
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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 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 Sensibilidade de fitobactérias às substâncias com propriedades antimicrobianas presentes em extratos de folhas de fumo inoculadas do patógeno incompatível Pseudomonas syringae pv. pisi(Revista Ceres, 1990-05) Silva, Talmir Duarte da; Romeiro, Reginaldo da SilvaPlantas de fumo (Nicotiana tabacum cv. 'Turkish' foram inoculadas de uma suspensão de células do patógeno incompatível Pseudomonas syringae pv. pisi. Vinte e quatro horas após, porções do limbo foliar, com sintomas típicos de reação de hipersensibilidade, foram submetidas à extração, pelo método de difusão facilitada (17), em etanol, a 40%. O extrato etanólico, concentrado, a vácuo, foi fracionado com acetato de etila. A fração acetato de etila revelou conter substâncias com propriedades antimicrobianas. Fitobactérias patogênicas para o fumo revelaram-se insensíveis à atividade presente no extrato, ao passo que as não-patogênicas para o fumo tiveram sua mutiplicação inibida.Item Effect of kind and method of fungicidal treatment of bean seed on infections by the VA-mycorrhizal fungus Glomus macrocarpum and by the pathogenic fungus Fusarium solani(Plant and Soil, 1991-04) Gonçalves, E. J.; Muchovej, J. J.; Muchovej, Rosa M. C.To test the effect of seed treatment with fungicides on the development of mycorrhizal fungi, bean seeds were treated with fungicide dry or vehicled in the organic solvents, ethanol or dichloromethane and then planted in soil inoculated with the mycorrhizal fungus Glomus macrocarpum and/or the plant pathogenic fungus Fusarium solani. Measurements were made at 4 day intervals, to assess the presence of mycorrhizae or disease in the roots as well as top dry weight, root fresh weight and root length. Fungicidal seed treatment did not affect the initial occurrence of mycorrhizae, number of spores of G. macrocarpum in the soil or root length. Fresh weights of roots and dry weights of tops were greater in the presence of the mycorrhizal fungus. The onslaught of symptoms by F. solani was significantly retarded by treatment with fungicides plus mycorrhizal fungi or fungicides plus organic solvents.Item Compostos fenólicos, idade da folha e resistência do cafeeiro a Pseudomonas cichorii e Pseudomonas syringae, pv. garcae(Revista Ceres, 1991-11) Oliveira, José Rogério de; Romeiro, Reginaldo da silvaÉ fato, experimentalmente estabelecido, que folhas. novas de cafeeiro são mais suscetíveis à mancha aureolada (P. syringae pv. garcae) e mais resistentes ao crestamento-bacteriano (P. cichorii), ocorrendo o oposto com folhas velhas. Na pressuposição de que compostos fenólicos poderiam estar envolvidas nessa resistência, procedeu-se à extração de fenóis totais de folhas novas e velhas de cafeeiro (variedade 'Catuaí'). Bioensaios de difusão em gel mostraram que extratos de folhas velhas inibiam: P. syringae pv. garcae, mas não P. cichorii. Contudo, não aconteceu o inverso sem extratos de folhas novas. Cromatografia de camada fina de sílica-gel, seguida de bioautografia, com o fungo-teste Thielaviopsis paradoxa, revelou serem extratos de folhas novas o velhas diferentes, no que tange à composição, em substâncias com propriedade antimicrobiana. Se compostos fenólicos podem explicar a suscetibilidade diferencial aos ásia patógenos exibida por folhas velhas de cafeeiro, deve haver outros mecanismos de resistência suscetibilidade que governam o fenômeno inverso em folhas novas.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 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 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,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 Detecção, isolamento e identificação de fungos predadores de nematóides em amostras de solo de diferentes regiões do Brasil(Revista Ceres, 1995-11) Dias, Waldir Pereira; Ferraz, Silamar; Muchovej, James JohnCento e cinquenta amostras de solo procedentes de diferentes regiões do Brasil foram examinadas para se detectar a presença de fungos predadores de nematóides. Obtiveram-se 12 isolados de Arthrobotrys muszjformis, quatro de A. conoides, dois de A. robusta, um de A. thaumasia, um de Monacmsporium gephympagum e um outro isolado de Monacrosporium, que se trata de uma espécie nova. Todos os fungos formam redes adesivas como órgão de captura dos nematóides, exceto a espécie de Monacrosporium ainda não identificada, que o faz por meio de nódulos adesivos.Item Nematóides associados ao cafeeiro no estado do Espírito Santo(Revista Ceres, 1996-11) Dias, Waldir Pereira; Liberato, José Ricardo; Fonseca, Aymbré Francisco Almeida daA nematological survey was carried out in 1992 in the coffee production area of Espírito Santo State, Brazil, to know the different genera of coffee parasitic nematodes in that State. The phytonematodes found and their frequencies (%) in the samples were: 1)Coffea arabica: Helicotylenchus sp. (68.8), Meloidogyne ' exigua (35.5), Aphelenchus sp. (33.3), Criconemellazsp. (20.0), Xiphinema sp. (13.3), Pratylenchussp. (13.3), Ditylenchus sp. (17.7), Aphelenchoides sp. (17.7), Tylenchus sp. (4.4), Meloidogyne sp. (juveniles) (2.0) and Rotylenchulus sp. (2.2). 2)Coffea canephora var. kouillou: Aphelenchus sp. (56.3), Helicotylenchus sp. (25.0), Ditylenchus sp. (21.9), Meloidogyne sp. (iuveniles) (20.3), Pratylenchus sp. (17.2), Tylenchus sp. (15.6), Aphelenchoides sp. (14.0), Cri- conemella sp. ( 10.9), Rotylenchulus Sp. (10.9) and Xiphinema sp. (1.5).Item Isoenzyme analysis of Arthrobotrys, a nematode-trapping fungus(Brazilian Journal of Medical and Biological Research, 1997-06-28) Araújo, J.V.; Junghans, T.G.; Alfenas, A.C.; Gomes, A.P.S.Extraction and isoenzyme analysis of four isolates of rthrobotrys including A. musiformis, A. robusta and A. conoides were conducted. Among the 14 enzymes studied by starch gel electrophoresis, using morpholine-citrate as gel/electrode buffer, the following nine enzymes showed interpretable banding patterns: α-esterase, fumarase, hexokinase, isocitrate dehydrogenase, leucine aminopeptidase, malate dehydrogenase, 6-phosphogluconate dehydrogenase, phosphogluco- mutase and phosphoglucoisomerase. All isolates studied displayed typical isoenzyme phenotypes for each species. Two isolates of A. conoides differed in their α-isoesterase banding patterns, but no differences were observed for the other enzymes. The assay was satisfactory for enzyme extraction and resolution of Arthrobotrys and could be used in future taxonomic and genetic studies of this organism.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 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 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.Item Atividade bacteriocinogênica entre isolamentos de Xanthomonas campestris pv. Arracaciae(Revista Ceres, 1999-01) Siqueira, Marita Francisca de; Romeiro, Reginaldo da SilvaTwenty four isolates of Xanthomonas campestris pv. arracaciae were tested against each other for production and sensibility of bacteriocins, Only five isolates behaved as producers and two did work as indicators. This is the first report on bacteriocin production by the pathovar.Item Queima bacteriana (Xanthomonas campestris) do alho-poró (Allium porrum) em Minas Gerais, Brasil(Revista Ceres, 1999-01) Moura, Andréa Bittencourt; Romeiro, Reginaldo da SilvaA leek disease found in Vicosa, Minas Gerais, showed pale apical lesions progressing downward from the leaf apex which later became necrotic. These leaves are completely taken up by the infection, dry up and fall off, while the plant remains alive. One bacterium producing medium yellow, shining, regularly edged, elevated colonies was isolated in a standard culture medium. It was unable to induce HR in beans, coffee, passion fruit, tobacco and tomato but induced the same observed leaf symptoms when reinoculated into healthy leek plants. The isolated bacteria are straight, regular, rod-shaped, Gram-negative cells, unable to use asparagine, strict aerobes, xanthomonadin-producers, non tumorogenic and can be positioned in Xanthomonas. Biochemical tests identified X. campestris as the species. The disease may be seed transmitted.