982 resultados para Canker (Plant disease)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Rhizoctonia foliar blight (RFB) of soybean [Glycine max (L.) Merrill] occurs in many tropical and subtropical regions, causing yield reductions of up to 70% and in Brazil, up to 60%. The disease is caused by Rhizoetonia solani AG1-IA and AG1-IB, and by AG2-3 in Japan. RFB occurs in the North, Northeast and Mid-west regions of Brazil. Chemical control remains the only effective method of controlling RFB, but its efficiency depends upon environmental conditions. In this study, 18 fungicides, salicylic acid (SA) and acibenzolar-s-methyl (ASM) were evaluated on R. solani AG1-IA in vitro, by mycelial growth rating and estimating effective concentration for 50% (EC 50) and 90% (EC 90) inhibition of mycelial growth, and in vivo by reduction of disease severity on soybean plants in greenhouse conditions. Mycelial growth was strongly inhibited by the fungicides pyraclostrobin + boscalid and fludioxonil. Preventive fungicide applications were the most effective. Strobilurins were more efficient both in preventive and curative applications. Best results with plant resistance activators were obtained with SA (2.5 mM) sprayed at 20 d before inoculation and with ASM (12.5 mg a.i. l(-1)) 10 d before inoculation. (c) 2005 Elsevier Ltd. All rights reserved.
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Xylella fastidiosa is a xylem-dwelling, insect-transmitted, gamma-proteobacterium that causes diseases in many plants, including grapevine, citrus, periwinkle, almond, oleander, and coffee. X. fastidiosa has an unusually broad host range, has an extensive geographical distribution throughout the American continent, and induces diverse disease phenotypes. Previous molecular analyses indicated three distinct groups of X.fastidiosa isolates that were expected to be genetically divergent. Here we report the genome sequence of X. fastidiosa (Temecula strain), isolated from a naturally infected grapevine with Pierce's disease (PD) in a wine-grape-growing region of California. Comparative analyses with a previously sequenced X.fastidiosa strain responsible for citrus variegated chlorosis (CVC) revealed that 98% of the PD X.fastidiosa Temecula genes are shared with the CVC X. fastidiosa strain 9a5c genes. Furthermore, the average amino acid identity of the open reading frames in the strains is 95.7%. Genomic differences are limited to phage-associated chromosomal rearrangements and deletions that also account for the strain-specific genes present in each genome. Genomic islands, one in each genome, were identified, and their presence in other X.fastidiosa strains was analyzed. We conclude that these two organisms have identical metabolic functions and are likely to use a common set of genes in plant colonization and pathogenesis, permitting convergence of functional genomic strategies.
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Xylella fastidiosa is a phytopathogen that causes diseases in different plant species. The development of disease symptoms is associated to the blockage of the xylem vessels caused by biofilm formation. In this study, we evaluated the sensitivity of biofilm and planktonic cells to copper, one of the most important antimicrobial agents used in agriculture. We measured the exopolysaccharides (EPS) content in biofilm and planktonic cells and used real-time reverse transcription polymerase chain reaction to evaluate the expression of the genes encoding proteins involved in cation/multidrug extrusion (acrA/B, mexE/czcA, and metI) and others associated with different copper resistance mechanisms (copB, cutA1, cutA2, and cutC) in the X. fastidiosa biofilm formed in two different media. We confirmed that biofilms are less susceptible to copper than planktonic cells. The amount of EPS seems to be directly related to the resistance and it varies according to the media where the cells are grown. The same was observed for gene expression. Nevertheless, some genes seem to have a greater importance in biofilm cells resistance to copper. Our results suggest a synergistic effect between diffusion barriers and other mechanisms associated with bacterial resistance in this phytopathogen. These mechanisms are important for a bacterium that is constantly under stress conditions in the host.
PLANT-TO-SEED TRANSMISSION of CURTOBACTERIUM FLACCUMFACIENS pv. FLACCUMACIENS IN A DRY BEAN CULTIVAR
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Stem canker caused by the fungus Diaporthe phaseolorum f. sp. meridionalis is a disease that limits soybean cultivation. Phenotypic evaluations aiming at disease resistance require labor-intensive processes, as for instance handling and transport of phytopathogens. The use of DNA markers in the selective procedures eases certain phases, besides being practical, safe and reliable. A RAPD fragment of 588pb was identified among bulks of resistant and susceptible plants in the cross BR92-15454 (R) x IAC-11 (S). Through co-segregation, the distance between the resistance locus and the fragment was estimated at 7.4 ± 2.1 cM, with a Lodmax. of 23.072 (first year) and at 6.0 ± 3.4 cM with a Lodmax. of 7.806 (second year). The fragment was converted into a SCAR marker and digested with enzyme Hinc II, which made the classification in homozygous resistant, heterozygous resistant and susceptible plants possible. This SCAR marker is suitable for use in the improvement program conducted in Jaboticabal.
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Sickle Cell Disease (SCD) is one of the most prevalent hematological diseases in the world. Despite the immense progress in molecular knowledge about SCD in last years few therapeutical sources are currently available. Nowadays the treatment is performed mainly with drugs such as hydroxyurea or other fetal hemoglobin inducers and chelating agents. This review summarizes current knowledge about the treatment and the advancements in drug design in order to discover more effective and safe drugs. Patient monitoring methods in SCD are also discussed. © 2011 Bentham Science Publishers Ltd.
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The fungus Rhizoctonia solani AG-1 IA causes sheath blight, one of the most important rice diseases worldwide. The first objective of this study was to analyse the genetic structure of R. solani AG-1 IA populations from three locations in the Iranian Caspian Sea rice agroecosystem. Three population samples of R. solani AG-1 IA isolates were obtained in 2006 from infected rice fields separated by 126-263km. Each field was sampled twice during the season: at the early booting stage and 45days later at the early mature grain stage. The genetic structure of these three populations was analysed using nine microsatellite loci. While the population genetic structure from Tonekabon and Amol indicated high gene flow, they were both differentiated from Rasht. The high gene flow between Tonekabon and Amol was probably due mainly to human-mediated movement of infested seeds. The second objective was to determine the importance of recombination. All three populations exhibited a mixed reproductive mode, including both sexual and asexual reproduction. No inbreeding was detected, suggesting that the pathogen is random mating. The third objective was to determine if genetic structure within a field changes over the course of a growing season. A decrease in the proportion of admixed genotypes from the early to the late season was detected. There was also a significant (P=0·002) increase in the proportion of loci under Hardy-Weinberg equilibrium. These two lines of evidence support the hypothesis that basidiospores can be a source of secondary inoculum. © 2012 BSPP.
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Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)