Nano-Magnesium Oxide: A Novel Bactericide Against Copper-Tolerant Xanthomonas perforans Causing Tomato Bacterial Spot.

Bacterial spot caused by Xanthomonas perforans causes significant damage on tomato in Florida. Due to the presence of copper (Cu)-tolerant X. perforans strains, Cu bactericides are not effective in disease management. Hence, there is a critical need to find alternatives for Cu. Antibacterial activity of magnesium oxide (Nano-MgO), and other metal oxide nanoparticles, were evaluated against a Cu-tolerant and -sensitive X. perforans strain. In vitro experiments demonstrated high antibacterial activity of Nano-MgO against both strains compared with the commercial Cu. The minimum inhibitory concentration of Nano-MgO is 25 µg/ml and the minimum bactericidal concentration is 100 µg/ml against a Cu-tolerant X. perforans strain after 4 h of exposure. Structural changes in the bacterial membrane following exposure to Nano-MgO treatments compared with the controls were observed using transmission electron microscopy. In two greenhouse experiments with a Cu-tolerant strain, bacterial spot severity was significantly reduced by Nano-MgO at 200 µg/ml compared with Cu-ethylene bis-dithiocarbamate (grower standard), and the untreated control (P = 0.05). In three field experiments, Nano-MgO at 200 µg/ml significantly reduced disease severity with no negative impact on yield compared with the untreated control. Inductively coupled plasma mass spectrometric analysis of the fruit confirmed that Nano-MgO application did not lead to the accumulation of Mg, Cu, Ca, K, Mn, P, and S. This study is the first to demonstrate the potential of Nano-MgO against bacterial spot of tomato.

Trace elements concentrations in Buff-breasted Sandpiper sampled in Lagoa do Peixe National Park, Southern Brazil.

Cadmium, cobalt, chromium, copper, manganese, nickel, zinc and lead concentrations were detected in feathers of Buff-breasted Sandpipers (Calidris subruficollis) captured during the non-breeding season and analyzed with relationship to body mass. Of these metals tested for, only copper levels (2.28 µg/g) were positively correlated with bird body mass. Zinc levels showed higher concentration (67.97 µg/g) than the other metals, and cadmium levels showed the lowest concentration (0.14 µg/g). Trace element concentrations were below toxicity levels for all tested chemicals and we suggest that this probably reflects that essential elements are maintained there by normal homeostatic mechanism and that no excessive environmental exposure to these elements during migration or on the wintering area is suggested by these results.

Trace elements concentrations in Buff-breasted Sandpiper sampled in Lagoa do Peixe National Park, Southern Brazil / Concentração de elementos-traço em maçarico-acanelado amostrados no Parque Nacional da Lagoa do Peixe, Sul do Brasil

Abstract Cadmium, cobalt, chromium, copper, manganese, nickel, zinc and lead concentrations were detected in feathers of Buff-breasted Sandpipers (Calidris subruficollis) captured during the non-breeding season and analyzed with relationship to body mass. Of these metals tested for, only copper levels (2.28 µg/g) were positively correlated with bird body mass. Zinc levels showed higher concentration (67.97 µg/g) than the other metals, and cadmium levels showed the lowest concentration (0.14 µg/g). Trace element concentrations were below toxicity levels for all tested chemicals and we suggest that this probably reflects that essential elements are maintained there by normal homeostatic mechanism and that no excessive environmental exposure to these elements during migration or on the wintering area is suggested by these results.

Resumo As concentrações de cádmio, cobalto, cromo, cobre, manganês, níquel, zinco e chumbo foram detectadas em penas de Maçarico-acanelado (Calidris subruficollis) capturados durante o período de invernada e analisados em relação a massa corporal. Destes metais analisados, somente os níveis de cobre (2,28 µg/g) foram correlacionados positivamente com a massa corporal dos indivíduos. Níveis de zinco apresentaram-se mais altos (67,97 µg/g) que outros metais e os níveis de cádmio apresentaram as menores concentrações (0,14 µg/g). As concentrações dos elementos-traços estão abaixo dos níveis de toxicidade em todos os testes químicos e sugerimos que isto provavelmente ocorre pela manutenção dos elementos essenciais através do mecanismo normal de homeostase e não reflete a exposição destes elementos durante a migração ou nas áreas de invernada.