Assuntos
Dente Pré-Molar , Resinas Compostas , Colagem Dentária , Adaptação Marginal Dentária , Análise do Estresse Dentário , Vidro , Restaurações Intracoronárias , Teste de Materiais , Microscopia Eletrônica de Varredura , Cimentos de Resina , Estresse Mecânico , Propriedades de Superfície , Temperatura , Dente não VitalAssuntos
Condicionamento Ácido do Dente , Cerâmica , Resinas Compostas , Desenho Assistido por Computador , Dente Suporte , Colagem Dentária , Polimento Dentário , Porcelana Dentária , Planejamento de Dentadura , Retenção de Dentadura , Prótese Parcial Fixa , Vidro , Humanos , Óxido de Magnésio , Teste de Materiais , Microscopia Eletrônica de Varredura , Cimentos de Resina , Silanos , Estresse Mecânico , Propriedades de Superfície , Preparo Prostodôntico do Dente , ZircônioRESUMO
Target leaf spot was found on johnsongrass (Sorghum halepense (L.) Pers.) in La Plata, Argentina (34°54'S, 58°30'W). Up to 80% disease severity was observed in adult plants. In most diseased plants, spots were well defined, delimited by leaf veins, and elongated. Individual lesions ranged in size from small spots (2 to 3 mm) to large lesions (10 to 15 mm). Lesions sometimes coalesced to produce extensive areas of necrosis. Isolates identified as Bipolaris sorghicola (Lefebre & Scherwin) Alcorn (1) grew slowly on potato dextrose agar medium, producing a compact dark brown mycelium. Conidia were 40 to 80 µm long, slightly curved and golden brown, with three to seven pseudosepta. Although germination of conidia was mainly bipolar, lateral germination sometimes was observed. Twenty monoconidial isolates were inoculated at 105 conidia per cm3 on johnsongrass at the 4-leaf stage to confirm the pathogenicity of B. sorghicola. After inoculation, plants were placed in a high-humidity chamber for 24 h; thereafter, they were kept at 25°C day and 18°C night temperatures. Typical lesions developed after 10 days. The pathogen was reisolated from lesions after 15 days. Johnsongrass is one of the most noxious weeds in the world. Due to its potential as a biocontrol agent, further studies are needed to determine the effect of B. sorghicola on johnsongrass. Reference: (1) J. L. Alcorn. Mycotaxon 27:1, 1983.
RESUMO
Gliocladium roseumis a successful antagonist of Botrytis cinerea and is considered to have the major potential for biocontrol of the pathogen in cropping systems. In order to elucidate the optimal moment of the day to apply the biological control agent, geranium plants were inoculated until run off with a suspension containing 10 e7 conidia of G. roseum + Tritón 100X. The inoculation times were 9 am, 12 am, 3 pm and 6 pm. The number cfu per cm(2) of leaves at inoculation time (time 0) and at 3, 6 y 9 h after inoculation were estimated. Then, the inoculated plants were kept in a Plexiglas, humidity chamber for 24 h. Discs of 8 mm in diameter were cut off from the inoculated leaves and put then into a paraquat medium to examine the development of G. roseum. According to the results dry period length after inoculation time, shows a significant decrease in number of cfu by cm(2) of leaf. No difference was observed between 3, 6 y 9 h after inoculation time.
RESUMO
During the summer of 1995-1996, an 80-ha field of 6-year-old asparagus plants (cv. UC 72) in Saladillo (Province of Buenos Aires) was affected by a decline syndrome (1). The plants showed a decline in vigor and approximately 60 to 70% of the plants died. The symptomatic plants were chlorotic, stunted, with stem lesions and crown and root rot. Fusarium moniliforme and F. proliferatum were isolated from vascular and epidermal tissues of roots, crowns, and stems. Identification of Fusarium to species was made by examining conidiogenous cells from colonies cultured on KCl medium (2). Microconidia were born in long and short chains and false heads. The isolates were identified based on the the presence of polyphialides in F. proliferatum and their absence in F. moniliforme, which produces monophialides only (2). In two separate trials, asparagus seeds (cv. UC 72) were surface sterilized and placed in steamed soil infested with a conidial suspension of each species. The viable propagules in the soil (CFU per g) were estimated by soil plate dilutions on Nash & Snyder-PCNB (pentachloronitrobenzene) medium. The F. moniliforme and F. proliferatum soil densities were 19.2 × 103 and 23 × 103 CFU per g of soil, respectively. The pots were placed in the greenhouse on different benches to avoid cross-contamination. After 4 months, inoculated plants showed root and crown discoloration. F. moniliforme and F. proliferatum were reisolated (64 and 75%, respectively) from discolored portions of internal and external root and crown tissues. Although the stems did not show symptoms, F. moniliforme and F. proliferatum were also recovered (27 and 38%, respectively) from asymptomatic tissues. Six months after inoculation the plants developed chlorotic symptoms with crown and root rot, and then wilted. F. moniliforme and F. proliferatum were reisolated from root systems, crowns, and stems of all inoculated plants. F. moniliforme and F. proliferatum are involved in corn stalk and ear rot in Argentina. Corn and asparagus are frequently grown in close proximity and often follow one another at a particular site. Airborne and soil debris carrying F. moniliforme and F proliferatum from corn may be an additional source of inoculum for asparagus in Argentina. The results indicate that the presence of F. moniliforme and F. proliferatum is a factor that contributes to asparagus decline in Argentina. References: (1) W. H. Elmer et al. Plant Dis. 80:117, 1996. (2) P. E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. Pennsylvania State University, University Park, 1983.
RESUMO
The ability to parasitise Sclerotinia sclerotiorum and the effect on apothecia production was evaluated for the following antagonists: Trichoderma harzianum; Trichoderma koningii; Gliocladium roseum and Chaetomium globosum. Plastic trays were filled with of steam-sterilized soil. Each one of them was infested with sclerotia of S. sclerotiorum and the culture of the antagonists. The trays were kept in a greenhouse and after 30, 60 and 90 days, evaluations were made. The rates of carpogenic germination, myceliogenic germination, mycoparasitism and destruction were evaluated. To assess carpogenic germination, the sclerotia were put in a growth chamber over moistened filter paper at 20 -/+ 2 degrees C and 12 light hours. The rates of myceliogenic germination and mycoparasitism were evaluated on Petri dishes with 2% APD. Antagonists effect on carpogenic germination was observed one month after the start of the assay. In the evaluation made at 60 and 90 days, T. harzianum; T. koningii and G. roseum kept inhibitory properties. Such inhibition was not observed in the trays containing C. globosum. In the evaluations made at 30 days, mycoparasitism rate was high in the trays with T. harzianum; T. koningii and G. roseum. G. roseum and T. harzianum destroy S. sclerotiorum sclerotia.
RESUMO
Volatile compounds produced by Trichoderma hamatum were tested for their capacity to suppress in vitro the growth of Alternaria citri, Bipolaris cynodontis, Bipolaris sorokiniana, Curvularia brachyspora, Curvularia lunata, Curvularia oryzae-sativae, Drechslera tritici-repentis, Rhizoctonia solani, Sclerotinia minor and Sclerotium rolfsii. The organisms were cultured in an apparatus made with two Erlenmeyer flasks assembled by their top parts. With the aid of the gas chromatographic technique the variation of carbon dioxide, oxygen and ethylene in the internal system was determined. Acetaldehyde and ethanol were not found. Due to the respiratory metabolism of T. hamatum the carbon dioxide level progressively increased while the oxygen content decreased. Ethylene production was low and after three days remained constant. Excepting C. oryzae-sativae and B. cynodontis the other species showed changes in the growth and development. These results suggest the inhibitory volatiles of T. hamatum as one possible mechanism of biological control.
RESUMO
The antagonistic properties of seven Trichoderma species in front of the pathogens Fusarium oxysporum, F. equiseti, F. solani, Sclerotinia sclerotiorum, S. minor, Rhizoctonia sp. and Sclerotium rolfsii was evaluated in vitro. Those microorganisms were isolated from horticultural soils of La Plata in order to test the antagonistic-pathogenic relationship. Dual cultures on PDA 2% were used. All the species of Trichoderma grew in the culture medium with a colonization value higher than 50%. Differences in the antagonistic behaviour of the pathogens were observed depending on the species with which they interacted. The presence of diffusible metabolites to the medium was demonstrated in almost 80% of the pathogens antagonists tested.
Assuntos
Ascomicetos/fisiologia , Fungos/patogenicidade , Fusarium/fisiologia , Rhizoctonia/fisiologia , Microbiologia do Solo , Trichoderma/fisiologia , Argentina , Ascomicetos/patogenicidade , Fusarium/patogenicidade , Doenças das Plantas/microbiologia , Rhizoctonia/patogenicidadeRESUMO
Two methods were tested in order to determine the existence of in vitro antagonism among saprobic and pathogenic fungi. These microorganisms were the most common isolates from horticultural soils of La Plata (Buenos Aires). Trichoderma harzianum; T. koningii and Penicillium sp. were antagonistic to all the pathogenic fungi tested, Fusarium solani; F. oxysporum; Alternaria solani; Colletotrichum sp. and Sclerotium rolfsii Spicaria sp., Paecilomyces sp. and Chaetomiun sp. were antagonistic only to Colletotrichum sp. and Fusarium solani.
Assuntos
Fungos/isolamento & purificação , Microbiologia do Solo , Argentina , Fungos/fisiologia , Técnicas Microbiológicas , Especificidade da EspécieRESUMO
Two methods were tested in order to determine the existence of in vitro antagonism among saprobic and pathogenic fungi. These microorganisms were the most common isolates from horticultural soils of La Plata (Buenos Aires). Trichoderma harzianum; T. koningii and Penicillium sp. were antagonistic to all the pathogenic fungi tested, Fusarium solani; F. oxysporum; Alternaria solani; Colletotrichum sp. and Sclerotium rolfsii Spicaria sp., Paecilomyces sp. and Chaetomiun sp. were antagonistic only to Colletotrichum sp. and Fusarium solani.
RESUMO
Two methods were tested in order to determine the existence of in vitro antagonism among saprobic and pathogenic fungi. These microorganisms were the most common isolates from horticultural soils of La Plata (Buenos Aires). Trichoderma harzianum; T. koningii and Penicillium sp. were antagonistic to all the pathogenic fungi tested, Fusarium solani; F. oxysporum; Alternaria solani; Colletotrichum sp. and Sclerotium rolfsii Spicaria sp., Paecilomyces sp. and Chaetomiun sp. were antagonistic only to Colletotrichum sp. and Fusarium solani.