Effect of oil contamination on the properties of leached chernozem under model experimental conditions

A model experiment was performed to study the effect of soil contamination with oil on the growth of wheat plants. Neither significant downward migration of oil or oil components, including the most mobile aromatic hydrocarbons, in a column with leached chernozem nor removal of these compounds from the column were observed when the initial oil concentration was below 0.75%. These data confirmed the previous results that oil at a concentration of 0.3% had no negative effect on the growth of wheat. The synergetic effect of oil, soluble salts, and exchangeable sodium should be taken into account in the determination of maximum permissible residual oil content in soils.     

Variation in the response of melon genotypes to Fusarium oxysporum f.sp. melonis race 1 determined by inoculation tests and molecular markers

Screening of genotypes of melon ( Cucumis melo ) for resistance to wilt caused by Fusarium oxysporum f.sp. melonis is often characterized by wide variability in their responses to inoculation, even under carefully controlled conditions. The variability at the seedling stage of 17 genotypes susceptible to race 1 was examined in growth-chamber experiments. Disease incidence varied from 0 to 100% in a genotype-dependent manner. Using four combinations of light (60 and 90  µ E m⁻² s⁻¹) and temperatures of (27 and 31°C), only light intensity showed a statistically significant effect. Marker-assisted selection for fusarium resistance breeding using cleaved amplified polymorphic sequence (CAPS) and sequence-characterized amplified region (SCAR) markers were compared using a single set of genotypes that included 24 melon accessions and breeding lines whose genotype regarding the Fom-2 gene was well characterized. The practical value of the markers for discriminating a range of genotypes and clarifying the scoring of phenotypes was also tested using a segregating breeding population which showed codominant SCAR markers to be useful in marker-assisted selection.     

Effect of liming on extractable Zn, Cu, Fe and Mn in selected Scottish soils

Ten naturally acidic Scottish soils have been limed with CaCO₃ at 0,0.25, 0.50, 0.75, 1.00 and 1.25 times the recommended lime requirement, and then subjected to three cycles of alternate wetting to field capacity at 20°C for 1 month and drying for 1 month. The Zn, Cu, Fe and Mn extracted by DTPA solution, both at pH 7.3 and also after adjustment to match the final soil pH, were measured by flame AAS. The same elements were determined in ammonium acetate extracts, for extractants buffered at pH 4.8, pH 7.0 or at the final soil pH. The effect of extractant pH upon the amounts of trace elements removed is discussed for the two extractants, with particular reference to Zn. The influence of soil pH upon the amounts of trace elements extracted is also considered. There appears to be a distinct relationship between rate of decrease of DTPA-extractable Fe with increasing soil pH and the effect of pH upon DTPA-extractable Zn, high rates of decrease of extractable Fe being associated with a more continuous decline in extractable Zn with increasing soil pH. Possible reasons for this relationship are discussed, in the light of an experiment conducted to examine the effect of Fe and A1 on loss of Zn from solution at high pH. DTPA-extractable Cu varied little with increasing soil pH.     

Disease progression of a lethal decline caused by the 16SrIV‐D phytoplasma in Florida palms

Recently, a new phytoplasma was discovered in Hillsborough County in the state of Florida, USA. This phytoplasma belongs to the 16SrIV taxonomic group and is classified as subgroup D. It is the causal agent of lethal bronzing disease (LBD) of palm. Since the discovery of LBD in 2006, the disease has spread throughout much of the state. In 2014 and 2015, stands of cabbage palm and queen palms that had been present at the University of Florida's Fort Lauderdale Research and Education Center in Davie, FL began showing symptoms of LBD. After confirming the presence of the LBD phytoplasma in initially infected palms by nested PCR and RFLP analysis, all palms were systematically sampled over the period of 1 year to monitor and quantify disease spread. A total of 30 cabbage palms were tested monthly by qPCR, with five testing positive on the first sample date. By the end of the study period, 16 cabbage palms had died from the infection. A total of 16 queen palms were surveyed, with three palms initially testing positive. By the end of the study, four queen palms had tested positive and died from the infection. To the authors’ knowledge, this study is the first to document and quantify spread of palm‐infecting phytoplasmas. This data provides important insights into the ecology of palm‐infecting phytoplasmas and highlights the impact that the movement of infective insects can pose to established stands of palms.     

ADSORPTION OF PHOSPHATE BY GIBBSITE

The effects of the salts were studied using I per cent suspensions of gibbsite at pH 5.5 and 26°C. At 480μM phosphate and I mM calcium, the kinetic pattern was an initial rapid adsorption reaction, which approached equilibrium in 24 h, revealing a slower reaction. Adsorption isotherms determined at 24 h, with a range of final phosphate concentrations from 0.1 to 1000 μ in solution, were not affected by 20 mM sodium or potassium chloride or 10 mM magnesium chloride. Increasing calcium chloride from o to 20 TIM increased the adsorption of phosphate over the range from 1 to 100 μM final phosphate concentration. At lower (0.1 μM) and higher (1000 μM) phosphate, the effect of calcium was smaller. These results help to explain several effects of the various cations on the adsorption of phosphate by clays and soils, when effects of neutral salts on pH are also considered.     

Immunocytochemical localization of the Bacillus sphaericus binary toxin components in Culex quinquefasciatus (Diptera: Culicidae) larvae midgut

This study describes the immunocytochemical localization of the Bacillus sphaericus 2362 binary toxin components, BinA and BinB, in Culex quinquefasciatus larvae that had been intoxicated with this entomopathogen. Ultrathin sections of C. quinquefasciatus larvae midgut embedded in the hydrophilic resin L.R. White were incubated with the antibodies anti-BinA or anti-BinB and then revealed with goat anti-rabbit IgG coupled to gold particles. Immunocytochemical detection demonstrated the presence of specific labeling in ultra-thin sections that had been incubated with the BinA antiserum. Gold particles were detected on the apical areas of cell membranes and inside the epithelial cell cytoplasm, particularly the mitochondria, of cells from the gastric caeca and posterior stomach in larvae exposed during 2 or 24 h to the entomopathogen. A similar labeling pattern was observed in ultrathin sections from both midgut regions when incubated with BinB antiserum.     

Production of syringomycins and syringopeptins by Pseudomonas syringae pv. atrofaciens

All virulent strains of Pseudomonas syringae pv. atrofaciens produce in vitro substances with syringomycin-like features. All strains inhibited the growth of Geotrichum candidum in the plate assay although the extent of their growth inhibition was variable.
Purification of bioactive culture extracts of a highly virulent strain by ion exchange chromatography (Whatman CM52) yielded a main fraction which inhibited the growth of Rhodotorula pilimanae and Bacillus megaterium , and was phytotoxic to tobacco and wheat plants. In particular, the injection of this fraction in the culm of wheat plants caused phytotoxic symptoms on leaves similar to those caused in nature by the pathogen. The further purification by HPLC of the above fraction gave rise to four main bioactive substances which have been identified by spectroscopic methods (FAB-MS) and amino acid analysis as syringomycin E, syringomycin G, syringopeptin 25A and syringopeptin 25B, toxic lipodepsipeptides thus far recognized to be produced by most strains of P. syringae pv. syringae . The injection of both syringomycin E and syringopeptin 25A in wheat leaves caused necrotic symptoms; however, syringopeptin 25A was at least six times more active than syringomycin E. The possible role of the toxins in the disease development on cereals and the need for a careful examination of pathogenetic and biochemical features of P. syringae pv. atrofaciens to establish the relationships of the two pathovars in the 'syringae group' are discussed.     

Extent,Environmental Impact and Long-term Trends in Atmospheric Contamination in the Usa Basin of East-European Russian Arctic

Sediment cores and surface sediments from fourteen lakes locatedalong three pollution gradients in the Usa basin, north-east European Russia were analysed for diatoms, spheroidal carbonaceous particles, trace metals and water chemistry. At each site past pH was inferred using a diatom-based transfer function and critical loads for sulphur deposition were calculated using a diatom model. Lakes from the Vorkuta transectcurrently experience the highest levels of atmospheric deposition, however, results suggest that at present day sulphurdeposition levels there is no danger of lake acidification at any of the sites, due to their high buffering capacity. The sediment records show that sites from the Inta and Vorkuta transects experienced higher pollution loads 10–30 yr ago, whencoal production and mining were more intensive. There is also evidence that in the Vorkuta area atmospheric deposition mighthave led to the alkalisation of the lakes since diatom floristicchanges and an increase in inferred pH coincide with the periodof peak industrial activity.