Avaliação de produtos alternativos para o controle da mancha-bacteriana em tomateiro para processamento industrial.

O pôrometro de pós-colheita é um instrumento para medir transpiração, resistência difusiva e déficit de pressão de vapor por manometria a volume constante e por volumetria a pressão constante. É constituído de uma câmara de transpiração com fechamento hermético contendo um suporte de amostras sobre um ventilador e externamente um manômetro de coluna de água com pipeta graduada móvel. Sob temperatura constante, o déficit de pressão de vapor (.P), e o volume de vapor de água (.V) foram proporcionais aos volumes de água vaporizados. Com o uso de um excesso de água este aumento da pressão de vapor iguala-se, em módulo, ao déficit de pressão de vapor do ar na câmara de transpiração. Para amostras do ar atmosférico no laboratório, o déficit de pressão de vapor foi calculado a partir das temperaturas de bulbo seco e úmido em um psicrômetro ventilado e por manometria. A correlação entre estes dois métodos foi de 0,976. A acurácia das medidas de transpiração é tal que o produto do volume morto da câmara (V) pela declividade (.P/ .V) determinada pelo vapor de água liberado no processo iguala-se à pressão barométrica, com erro inferior a 1%. Um exemplo experimental do uso do porômetro de pós-colheita em cenoura é apresentado juntamente e os detalhes para obter a resistência difusiva e espessura da camada laminar. O porômetro de pós-colheita é um porômetro de difusão simples, robusto, que poderá ser usado em estudos de efeito de cêras, na seleção de cultivares e em variados outros estudos de fisiologia de pós-colheita.

Estimativas de parâmentros genéticos visando a seleção para resistência à queima-das-folhas em populações de cenoura do grupo Brasília.

2008

Detecção e identificação molecular de Xanthomonas spp. causadoras da mancha bacteriana do tomateiro.

Neste comunicado são relatados os procedimentos para a identificação molecular das quatro espécies de Xanthomonas associadas à mancha bacteriana do tomateiro.

The ecology of Bacillus thuringiensis on the Phylloplane: colonization from soil, plasmid transfer, and interaction with larvae of Pieris brassicae

Seedlings of clover (Triflorium hybridum) were colonized by Bacillus thuringiensis when spores and seeds were co-inoculated into soil. Both a strain isolated in the vegetative form from the phylloplane of clover, 2810-S-4, and a laboratory strain, HD-1, were able to colonize clover to a density of about 1000 CFU/g leaf when seeds were sown in sterile soil and to a density of about 300 CFU/g leaf in nonsterile soil. A strain lacking the characteristic insecticidal crystal proteins produced a similar level of colonization over a 5-week period as the wild type strain, indicating that crystal production was not a mitigating factor during colonization. A small plasmid, pBC16, was transferred between strains of B. thuringiensis when donor and recipient strains were sprayed in vegetative form onto leaves of clover and pak choi (Brassica campestris var. chinensis). The rate of transfer was about 0.1 transconjugants/recipient and was dependent on the plant species. The levels of B. thuringiensis that naturally colonized leaves of pak choi produced negligible levels of mortality in third instar larvae of Pieris brassicae feeding on the plants. Considerable multiplication occurred in the excreted frass but not in the guts of living insects. Spores in the frass could be a source of recolonization from the soil and be transferred to other plants. These findings illustrate a possible cycle, not dependent on insect pathology, by which B. thuringiensis diversifies and maintains itself in nature.

JAK2V617F homozygosity arises commonly and recurrently in PV and ET, but PV is characterized by expansion of a dominant homozygous subclone

Subclones homozygous for JAK2V617F are more common in polycythemia vera (PV) than essential thrombocythemia (ET), but their prevalence and significance remain unclear. The JAK2 mutation status of 6495 BFU-E, grown in low erythropoietin conditions, was determined in 77 patients with PV or ET. Homozygous-mutant colonies were common in patients with JAK2V617F-positive PV and were surprisingly prevalent in JAK2V617F-positive ET and JAK2 exon 12-mutated PV. Using microsatellite PCR to map loss-of-heterozygosity breakpoints within individual colonies, we demonstrate that recurrent acquisition of JAK2V617F homozygosity occurs frequently in both PV and ET. PV was distinguished from ET by expansion of a dominant homozygous subclone, the selective advantage of which is likely to reflect additional genetic or epigenetic lesions. Our results suggest a model in which development of a dominant JAK2V617F-homzygous subclone drives erythrocytosis in many PV patients, with alternative mechanisms operating in those with small or undetectable homozygous-mutant clones.

Identifying PV module mismatch faults by a thermography-based temperature distribution analysis

Photovoltaic (PV) solar power generation is proven to be effective and sustainable but is currently hampered by relatively high costs and low conversion efficiency. This paper addresses both issues by presenting a low-cost and efficient temperature distribution analysis for identifying PV module mismatch faults by thermography. Mismatch faults reduce the power output and cause potential damage to PV cells. This paper first defines three fault categories in terms of fault levels, which lead to different terminal characteristics of the PV modules. The investigation of three faults is also conducted analytically and experimentally, and maintenance suggestions are also provided for different fault types. The proposed methodology is developed to combine the electrical and thermal characteristics of PV cells subjected to different fault mechanisms through simulation and experimental tests. Furthermore, the fault diagnosis method can be incorporated into the maximum power point tracking schemes to shift the operating point of the PV string. The developed technology has improved over the existing ones in locating the faulty cell by a thermal camera, providing a remedial measure, and maximizing the power output under faulty conditions.

Thermography-based virtual MPPT scheme for improving PV energy efficiency under partial shading conditions

This paper proposes a new thermography-based maximum power point tracking (MPPT) scheme to address photovoltaic (PV) partial shading faults. Solar power generation utilizes a large number of PV cells connected in series and in parallel in an array, and that are physically distributed across a large field. When a PV module is faulted or partial shading occurs, the PV system sees a nonuniform distribution of generated electrical power and thermal profile, and the generation of multiple maximum power points (MPPs). If left untreated, this reduces the overall power generation and severe faults may propagate, resulting in damage to the system. In this paper, a thermal camera is employed for fault detection and a new MPPT scheme is developed to alter the operating point to match an optimized MPP. Extensive data mining is conducted on the images from the thermal camera in order to locate global MPPs. Based on this, a virtual MPPT is set out to find the global MPP. This can reduce MPPT time and be used to calculate the MPP reference voltage. Finally, the proposed methodology is experimentally implemented and validated by tests on a 600-W PV array. 

Chp8, a diguanylate cyclase from Pseudomonas syringae pv tomato DC3000 suppresses the PAMP flagellin, increases EPS and promotes plant immune evasion.

The bacterial plant pathogen Pseudomonas syringae causes disease in a wide range of plants. The associated decrease in crop yields results in economic losses and threatens global food security. Competition exists between the plant immune system and the pathogen, the basic principles of which can be applied to animal infection pathways. P. syringae uses a type III secretion system (T3SS) to deliver virulence factors into the plant that promote survival of the bacterium. The P. syringae T3SS is a product of the hypersensitive response and pathogenicity (hrp) and hypersensitive response and conserved (hrc) gene cluster, which is strictly controlled by the codependent enhancer-binding proteins HrpR and HrpS. Through a combination of bacterial gene regulation and phenotypic studies, plant infection assays, and plant hormone quantifications, we now report that Chp8 (i) is embedded in the Hrp regulon and expressed in response to plant signals and HrpRS, (ii) is a functional diguanylate cyclase, (iii) decreases the expression of the major pathogen-associated molecular pattern (PAMP) flagellin and increases extracellular polysaccharides (EPS), and (iv) impacts the salicylic acid/jasmonic acid hormonal immune response and disease progression. We propose that Chp8 expression dampens PAMP-triggered immunity during early plant infection.

Antioxidant activities of eight Algerian plant extracts and two essential oils

Total phenol, hydroxycinnamic acid derivatives, flavone/flavonol and flavanones/dihydroflavonol contents of hydro-alcoholic extracts, obtained by sonication, from the aerial parts of Artemisia campestris L., Anthemis arvensis L., Haloxylon scoparium Pomel, Juniperus phoenicea L., Arbutus unedo L., Cytisus monspessulanus L., Thymus algeriensis Boiss et Reut, Zizyphus lotus L (Desf.) collected in Djebel Amour (Sahara Atlas, Algeria) were quantified by spectrophotometric methods. The chemical composition of the essential oils obtained by hydrodistillation from Artemisia campestris L. and Juniperus phoenicea I aerial parts were also evaluated by gas chromatography (GC) and gas chromatography coupled to mass spectrometry (GC-MS). The antioxidant activity of the extracts and essential oils was assessed measuring the capacity for preventing lipid peroxidation using two lipidic substrates (egg yolk and liposomes), the capacity for scavenging DPPH, ABTS, superoxide anion radicals, hydroxyl radicals and peroxyl radicals. Anti-inflammatory activity was assessed by measuring the capacity for inhibiting lipoxygenase. Reducing power and chelating capacity were also assayed. The results showed different amounts of total phenols depending on the method used: A. campestris extract had the highest levels of total phenols when the measurement was made at lambda = 280 nm, whereas H. scoparium and A. unedo extracts showed the highest levels of total phenols with Folin-Ciocalteau. C. monspessulanus had the highest levels of flavones/flavonols and flavanones/dihydroflavonols. The essential oils of A. campestris and J. phoenicea were mainly constituted by alpha-pinene, beta-pinene and sabinene; and a-pinene, respectively. The methods used for assaying the capacity for preventing lipid peroxidation revealed to be inadequate for extracts due to the great interferences detected. The essential oils were more active than the generality of extracts for scavenging peroxyl radicals and for inhibiting lipoxygenase, whereas A. unedo extract was the most active for scavenging ABTS, DPPH, superoxide anion radicals and it also had the best reducing capacity. In a general way, the great majority of the antioxidant activities correlated well with the phenol content although such correlation was not so clear with the flavonoid content. (c) 2013 Elsevier B.V. All rights reserved.

PV inverters for module level applications

Dissertação para obtenção do Grau de Mestre em Energias Renováveis – Conversão Eléctrica e Utilização Sustentáveis