Contaminated irrigation water constitutes one of the main sources of plant pathogens that can cause disease and lead to potentially significant production losses in forest nurseries. Recycling of contaminated irrigation water increases the risk of spreading diseases. The objective of this study was to evaluate a simple slow sand filtration treatment of irrigation water as a method for eradicating fungal and bacterial pathogens in eucalypt cutting nurseries. Pilot filter units were constructed from PVC pipes containing a 80 cm high layer of sand with grain size varying from 0.50 to 0.75 mm, drainage layers of 10 cm of fine gravel (4 mm) followed by a 15 cm layer of coarse gravel (8 mm), connected to a water outlet. The PVC pipe had space for a 150 mm water column above the sand layer and the filter had a flow rate of 100 to 300 L m-2 h-1. Eradication of the bacterial pathogen Ralstonia solanacearum, and the fungal pathogens Cylindrocladium candelabrum and Botrytis cinerea through the use of the filter was evaluated. Detection of bacteria in filter-treated irrigation water was performed through the micro drop method followed by PCR of colonies, while fungal pathogens were detected using a castorbean leaf biological bait method. Evaluations were performed daily 35 times for R. solanacearum, 25 times for C. candelabrum and 18 times for B. cinerea during a period of 12 months. After the last evaluation period, samples from various depths of the sand layer in the filters were taken and analyzed for the presence of the plant pathogens. The slow sand filters were able to remove B. cinerea and C. candelabrum spores with 100% efficiency while eradication of R. solanacearum colonies reached up to 99.6%. Colonies of Trichoderma sp. were found predominantly on the all filter layers. The results of this study show that slow sand filters are efficient for recycled water in eucalypt nurseries, especially in eradicating fungal pathogens.

Avaliou-se o risco do reaproveitamento de água não tratada, originária do efluente do minijardim clonal, da casa de vegetação, da casa de sombra, das áreas de crescimento e rustificação a céu aberto de um viveiro clonal de eucalipto, quanto ao potencial de disseminação de inóculo de Botrytis cinerea e Cylindrocladium candelabrum. Avaliou-se também a presença de inóculo desses fungos em brita usada como cobertura do piso das áreas do viveiro. Para a detecção dos patógenos, empregaram-se discos de folhas de mamoneira (Ricinus communis) como isca. Análises periódicas evidenciaram que ambos os patógenos são constantemente veiculados na água não tratada, proveniente das diferentes fases da propagação clonal e sobre a brita, sendo C. candelabrum mais freqüentemente constatado. A composição e a concentração de sais de três soluções nutritivas, expressa em valores de condutividade elétrica (0, 0,5, 1,0, 1,5, 2,0, 2,5 e 3,0 mS.cm-1), não afetaram significativamente a germinação de conídios.

The risk posed by reuse of untreated water for irrigation, collected from the effluents of mini-hedges, greenhouses, shade houses, growing and hardening areas of a eucalyptus cutting nursery, was evaluated in relation to the dissemination of Botrytis cinerea and Cylindrocladium candelabrum. The presence of inocula of these fungi was also evaluated on gravel used as soil cover. For pathogen detection, leaf discs of castor bean (Ricinus communis) were employed as biological bait. Periodical analyses of water samples, collected in the nursery effluents, and of gravel, showed that both pathogens are frequently disseminated in the water of the effluents and the gravel used as soil cover, although C. candelabrum is most common. The composition and salt concentration of three nutrient solutions, expressed in electric conductivity values (0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mS.cm-¹) did not affect conidial germination of these two fungi.

Chagas' disease, caused by the protozoan Trypanosoma cruzi, is a major cause of cardiovascular disability in countries where it is endemic. Damage to the heart microvasculature has been proposed to be an important factor in the pathogenesis of heart dysfunction. Endothelin-1 (ET-1) is a potent vasoconstrictor and exerts its effects via specific ET A and ET B receptors. A few studies have suggested a role for ET-1 and its receptors in the pathogenesis of Chagas' disease. We investigated the effects of treatment with bosentan, an ET A/ET B receptor antagonist, on the course of T. cruzi infection (Y strain) in C57Bl/6 mice. Treatment with bosentan (100 mg kg-1 day-1) was given per os starting day 0 after infection until sacrifice. Bosentan significantly increased myocardial inflammation, with no effects on parasitemia. Although the total number of nests was similar, a lower number of intact amastigote nests was found in the heart of bosentan-treated animals. Bosentan failed to affect the infection-associated increase in the cardiac levels of the cytokines IFN-g and TNF-a and the chemokines CCL2/MCP-1, CCL3/MIP-1a and CCL5/RANTES. In vitro, pre-incubation with ET-1 (0.1 µM) 4 h before infection enhanced the uptake of the parasites by peritoneal macrophages, and this effect was abrogated when macrophages were pre-treated with bosentan (1 µM) 15 min before incubation with ET-1. However, ET-1 did not alter killing of intracellular parasites after 48 h of in vitro infection. Our data suggest that bosentan-treated mice have a delay in controlling parasitism which is compensated for exacerbated inflammation. Infection is eventually controlled in these animals and lethality is unchanged, demonstrating that ET-1 plays a minor role in the protection against acute murine T. cruzi infection.

Two Azospirillum brasilense open reading frames (ORFs) exhibited homology with the two-component NtrY/NtrX regulatory system from Azorhizobium caulinodans. These A. brasilense ORFs, located downstream to the nifR3ntrBC operon, were isolated, sequenced and characterized. The present study suggests that ORF1 and ORF2 correspond to the A. brasilense ntrY and ntrX genes, respectively. The amino acid sequences of A. brasilense NtrY and NtrX proteins showed high similarity to sensor/kinase and regulatory proteins, respectively. Analysis of lacZ transcriptional fusions by the ß-galactosidase assay in Escherichia coli ntrC mutants showed that the NtrY/NtrX proteins failed to activate transcription of the nifA promoter of A. brasilense. The ntrYX operon complemented a nifR3ntrBC deletion mutant of A. brasilense for nitrate-dependent growth, suggesting a possible cross-talk between the NtrY/X and NtrB/C sensor/regulator pairs. Our data support the existence of another two-component regulatory system in A. brasilense, the NtrY/NtrX system, probably involved in the regulation of nitrate assimilation.