Fitopatologia - Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11741
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Item Efeitos de diferentes níveis de matéria orgânica no solo e de inóculo sobre a interação planta-Meloidogyne spp. e a produção massal de Pasteuria penetrans(Summa Phytopathologica, 2007-10) Freitas, Leandro Grassi de; Alves, Fábio Ramos; Martinelli, Paulo Roberto Pala; Meira, Renata Maria Strozi Alves; Ferraz, Silamar; Demuner, Antônio Jacinto; Jesus Júnior, Waldir de Cintra; Borges, Eduardo Euclydes De L.Foram estudados os efeitos de quatro proporções de esterco de curral no solo, 0, 20, 33 e 50% (V:V), e três níveis de inóculo de Meloidogyne spp. (3.000, 6.000 e 9.000 J2 por planta) na concentração de fenóis em raízes de tomateiro, no desenvolvimento das fêmeas, nas células gigantes induzidas por esses patógenos e na infecção e reprodução de Pasteuria penetrans. O experimento foi conduzido em casa-de-vegetação, em delineamento inteiramente ao acaso com doze repetições, sendo avaliado 50 dias após a inoculação das plantas. O tamanho médio das fêmeas do nematóide foi maior quando as plantas foram inoculadas com 3.000 J2. Maior percentual de fêmeas infectadas por P. penetrans foi observado quando não se utilizou esterco no substrato ou quando as plantas foram inoculadas com 3.000 J2. As plantas inoculadas com 9.000 J2 e cultivadas no substrato com 20% de esterco foram as que produziram mais endósporos. A concentração de fenóis nas raízes aumentou à medida que se acrescentou esterco de curral ao substrato. As células gigantes de plantas cultivadas no substrato com 33 e 50% de esterco apresentaram menores número, tamanho e quantidade de núcleos. O aumento da proporção de esterco de curral ao substrato causou aumento nas concentrações de fenóis nas raízes, fato que foi deletério às células gigantes, prejudicial ao desenvolvimento do nematóide e à reprodução de P. penetrans.Item Induction of systemic resistance in tomato by the autochthonous phylloplane resident Bacillus cereus(Pesquisa Agropecuária Brasileira, 2006-08) Halfeld-Vieira, Bernardo de Almeida; Vieira Júnior, José Roberto; Romeiro, Reginaldo da Silva; Silva, Harllen Sandro Alves; Baracat-Pereira, Maria CristinaThe objective of this work was to verify if the induced resistance mechanism is responsible for the capacity of a phylloplane resident bacteria (Bacillus cereus), isolated from healthy tomato plants, to control several diseases of this crop. A strain of Pseudomonas syringae pv. tomato was used as the challenging pathogen. The absence of direct antibiosis of the antagonist against the pathogen, the significant increase in peroxidases activity in tomato plants exposed to the antagonist and then inoculated with the challenging pathogen, as well as the character of the protection, are evidences wich suggest that biocontrol efficiency presented by the antagonist in previous works might be due to induced systemic resistance (ISR).Item Efficiency of phylloplane bacteria in controlling aerial tomato diseases under field conditions(Summa Phytopathologica, 2008-01) Halfeld-Vieira, Bernardo A.; Romeiro, Reginaldo S.; Mounteer, Ann; Mizubuti, Eduardo S.G.The capacity of two bacteria isolated from the tomato phylloplane to control late blight (Phytophthora infestans) was investigated in the field, and compared against the effectiveness of spraying with the fungicide chlorothalonil (1.5 g a.i. L-1 ) or water (control). A 55% reduction in late blight intensity was observed in the leaves of the middle of the plant and 62% in those of the upper leaves when using the antagonist UFV-STB 6 ( Novosphingobium capsulatum ) as compared to the control. Isolate UFV-IEA 6 (Bacillus cereus) was able to reduce disease intensity by 55%, but only in the upper leaves of the tomato plants. Treatment with isolate UFV-STB 6 also led to a significant reduction in the percentage of fruits with late blight symptoms. The results demonstrate the potential of these two bacteria in controlling this disease.Item Selection of Clonostachys rosea isolates from Brazilian ecosystems effective in controlling Botrytis cinerea(Biological Control, 2005-08) Nobre, Sérgio A. M.; Maffia, Luiz Antônio; Mizubuti, Eduardo S. G.; Cota, Luciano Viana; Dias, Ana Paula S.Clonostachys spp. were isolated from soil samples, and living and dead leaves of different plant species. Twelve isolates which sporulated well when cultured on agar media were compared regarding the capacity of establishing and suppressing Botrytis cinerea in leaves of Rosa hybrida ‘Sandra,’ Fragaria × ananassa ‘Dover,’ Lycopersicon esculentum ‘Kada,’ and Eucalyptus globulus. The isolates established in leaves of each plant species, but leaf area with conidiophores (SFCA) varied with the stage of leaf development. In rose, SFCA varied from 3.0 to 13.9% on senescing leaves and 3.4 to 10.0% on green leaves. SFCA was higher in young leaves of E. globulus and tomato (1.4–15.6% and 1.4–8.0%, respectively) than on senescing leaves (0.8–3.5% and 1.0–5.2%, respectively). In strawberry, SFCA varied from 0.7 to 6.2% on completely expanded leaves. Clonostachys rosea isolates reduced B. cinerea sporulation on leaves of rose (81.0–97.4% reduction), strawberry (87.6–96.8%), E. globulus (63.7–89.7%), and tomato (100% reduction). Four isolates of C. rosea were selected based on high levels of SFCA and suppression of B. cinerea. When leaf discs of the four hosts inoculated with these C. rosea isolates were challenged with isolates of B. cinerea of variable levels of aggressiveness, SFCA and pathogen suppression varied with the combination. Efficiency of C. rosea isolates in suppressing sporulation of B. cinerea varied among hosts but was always above 80%. The four selected Brazilian isolates of C. rosea are potential biocontrol agents for Botrytis blight management in Brazilian agricultural systems.Item Biocontrol of tomato late blight with the combination of epiphytic antagonists and rhizobacteria(Biological Control, 2006-09) Lourenço Júnior, Valdir; Maffia, Luiz A.; Romeiro, Reginaldo da Silva; Mizubuti, Eduardo S. G.Control of tomato late blight (LB) in Brazil is heavily based on chemicals. However, reduction in fungicide usage is required in both conventional and organic production systems. Assuming that biological control is an alternative for LB management, 208 epiphytic microorganisms and 23 rhizobacteria (RB) were isolated from conventional and organically grown tomato plants and tested for antagonistic activity against Phytophthora infestans. Based on in vitro inhibition of sporangia germination and detached leaflet bioassays, four EP microorganisms (Aspergillus sp., Cellulomonas flavigena, Candida sp., and Cryptococcus sp.) were selected. These microorganisms were applied either singly or combined on tomato plants treated or not with the RB Bacillus cereus. On control plants, LB progress rate (r), area under disease progress curve, and final disease severity were high. Lowest values of final severity were recorded on plants colonized by B. cereus and treated with C. flavigena, Candida sp. and Cryptococcus sp. There was no reduction on disease severity in plants treated only with RB. Biological control of LB resulted in low values of r and final severity. Integration of biological control with fungicides, cultural practices, and other measures can contribute to manage LB on tomato production systems.Item Pseudocercospora cryptostegiae-madagascariensis sp. nov. on Cryptostegia madagascariensis, an Exotic Vine Involved in Major Biological Invasions in Northeast Brazil(Mycopathologia, 2008-04-18) Silva, Janaina L. da; Barreto, Robert W.; Pereira, Olinto L.Cryptostegia madagascariensis is a plant native from Madagascar, belonging to the Apocynaceae that is invading the native vegetation in Northeast Brazil and threatening the unique riverine formations dominated by the carnauba palm. Individuals of C. madagascariensis cultivated in the campus of the Universidade Federal de Viçosa, state of Minas Gerais, Brazil, showing leaf spot symptoms of unknown etiology were observed. Two fungal species were found associated to such leaf spots: Colletotrichum gloeosporioides and a new species of Pseudocercospora. The latter was named Pseudocercospora cryptostegiae-madagascariensis and described herein. The discovery of those two fungal pathogens on C. madagascariensis coincide with the recognition that the weedy vine that is involved in the infestations in the Northeast of Brazil is not Cryptostegia grandiflora as formerly reported. These mycological findings are of greater importance now since C. madagascariensis is likely to become a target for biological control together with its former status in Brazil of an ornamental plant of limited relevance.Item Potencialidade antagonística detectada em alguns procariotas agentes de biocontrole de enfermidades de plantas(Summa Phytopathologica, 2007-12-20) Barra, Victor Rafael; Silva, Reginaldo da; Hélio, Glelson Maciel Ferraz; Macagnan, Dirceu; Silva, Harllen Sandro Alves; Moura, Andréa Bittencourt; Halfeld-Vieira, Bernardo de Almeida; Mendonça, Henrique Lopes; Júnior, José Roberto VieiraAo longo de vários anos, no Laboratório de Bacteriologia de Plantas e Controle Biológico (LBPCB) do Departamento de Fitopatologia da Universidade Federal de Viçosa têm-se, sistematicamente, isolado, de rizosfera, rizoplano e filoplano de plantas cultivadas de importância econômica, milhares de procariotas os quais são testados, um a um, como agentes de biocontrole de enfermidades. A grande maioria deles, como esperado, não exibe qualquer potencialidade como agente de biocontrole e é descartada. Alguns poucos são selecionados, através de demorados ensaios de biocontrole experimental tanto em casa de vegetação como em campo. Neste trabalho, mostra-se que muitos dos organismos em estudo, mesmo havendo sido selecionados, principalmente, por induzirem resistência sistêmica na planta alvo, expressam constitutivamente mecanismos de antagonismo microbiano que parecem fazer parte de seu perfil enquanto agentes de biocontrole.