Biological and molecular characterization of two closely related carlaviruses affecting brassica plants

Carlaviruses are plant-infecting viruses with flexuous filamentous particles of approximately 650 nm in length and a positive single-stranded hexacistronic RNA molecule as the genome. In this study, we analysed 14 samples of brassicas plants, reportedly affected by carlaviruses, that were collected in distant and edaphoclimatic distinct regions in Brazil. The genomes of four viral isolates detected in leaf kale (Brassica oleracea var. acephala) plants displayed the typical genomic organization of carlaviruses, subdivided into two contrasting identity profiles. Isolates T25, T107, and T110 showed a higher sequence identity among them (c.93%) than with T90 (c.67%), which had the highest nucleotide sequence identity (85.2%) with the only documented genomic fragment, approximately 1 kb of the RNA 3′-end, of cole latent virus (CoLV). Identity values among the other three isolates and CoLV were consistently lower than 78.6%. Nucleotide and amino acid sequence identity values of the replicase cistron of the isolates T25 and T90 are below the threshold for species demarcation in the genus Carlavirus. Upon mechanical transmission, these two isolates induced different symptoms in brassicas and solanaceous plants. Overall, data indicated that these viruses belong to two related but distinct species of carlaviruses. While T90 was recognized as an isolate of CoLV, the remaining isolates were considered members of a new tentative carlavirus named Cole mild mosaic virus (CoMMV). Current work provides convincing support for the taxonomic status of the species Cole latent virus, enlarges the known diversity of carlaviruses, and makes available new molecular tools to improve surveys of brassica-infecting viruses.     

Infection of cattle in Queensland with bluetongue viruses: 1. prevalence of antibodies

SUMMARY A survey of nearly 20 000 cattle in Queensland was conducted to describe the prevalence and distribution of infection by serotypes of bluetongue virus. The overall prevalence of serum antibodies to one or more bluetongue viruses was 8.7% (95% confidence interval 8.3 to 9.1). Sera from cattle contained neutralising activity against 2 serotypes, 1 and 21. No evidence was found of infection with other serotypes previously isolated in Australia. The overall prevalence of serotype 1 antibodies was 7.7% (95% CI 7.3 to 8.0) and the prevalence of serotype 21 antibodies was 3.3% (95% CI 3.1 to 3.6). The prevalence of serotype 1 antibodies was significantly (P < 0.05) higher than that of serotype 21 in every region of the State, except in the central highlands and south-west Queensland. Overall, 3 significantly (P < 0.05) different zones of prevalence were found: high prevalence (> 20%) in far north Queensland, moderate (5 to 20%) in north-west, northern and southern coastal Queensland, and low (< 5%) in the central highlands, Darling Downs and south-west Queensland.     

Effect of liming on hexazinone sorption and desorption behavior in various soils

Liming is a practice commonly used to modify soil acidity, neutralize aluminum, and increase calcium and magnesium in the soil. Liming can change herbicide retention processes and consequently weed control and potential environmental contamination. The effects of liming on the sorption and desorption of hexazinone in different soils were evaluated. Samples from seven Brazilian soils were collected and separated into two subsamples, with and without limestone incubation. Hexazinone was quantified using ultra high-performance liquid chromatography. The sorption and desorption coefficients were determined in soils using Freundlich isotherms. Increasing the pH did not alter the sorption kinetics of hexazinone in the same soil class. The shortest sorption time of hexazinone occurred in soils with higher organic matter (OM) and clay content. Liming reduced the sorption and increased the desorption of hexazinone in the soils, which was caused by the increase in pH and reduction of OM content. Although the application of limestone increased desorption, the rate at which this process occurred was less than the sorption rate of hexazinone in most cases. In alkaline soils, the recommended dose of hexazinone for pre-emergence application should be low to avoid leaching and reduce the contamination of groundwater resources.     

Responses to water stress in two Eucalyptus globulus clones differing in drought tolerance

We evaluated drought resistance mechanisms in a drought-tolerant clone (CN5) and a drought-sensitive clone (ST51) of Eucalyptus globulus Labill. based on the responses to drought of some physiological, biophysical and morphological characteristics of container-grown plants, with particular emphasis on root growth and hydraulic properties. Water loss in excess of that supplied to the containers led to a general decrease in growth and significant reductions in leaf area ratio, specific leaf area and leaf-to-root area ratio. Root hydraulic conductance and leaf-specific hydraulic conductance decreased as water stress became more severe. During the experiment, the drought-resistant CN5 clone maintained higher leaf water status (higher predawn and midday leaf water potentials), sustained a higher growth rate (new leaf area expansion and root growth) and displayed greater carbon allocation to the root system and lower leaf-to-root area ratio than the drought-sensitive ST51 clone. Clone CN5 possessed higher stomatal conductances at moderate stress as well as higher hydraulic conductances than Clone ST51. Differences in the response to drought in root biomass, coupled with changes in hydraulic properties, accounted for the clonal differences in drought tolerance, allowing Clone CN5 to balance transpiration and water absorption during drought treatment and thereby prolong the period of active carbon assimilation.     

Crambe Growth in a Soil Amended with Biochar and under Saline Irrigation

Biochar is the term given to biomass subjected to the process of change in the composition by the action of high temperatures. Advantages of biochar in soil quality have been reported, including amelioration of salinity effects. Crambe has great potential to figure as raw material for biofuel, since it naturally contains up to 60% of erucic acid. This study evaluated crambe growth in a soil amended with biochar and irrigated with saline waters. A greenhouse experiment was conducted following a completely randomized design with five levels of biochar, two irrigation water supplies, and four replications. Parameters related to soil chemical properties, crambe growth, oil, and macronutrient contents were evaluated. Biochar presented significance for pH, electrical conductivity (EC), organic matter (OM), phosphorus (P), sodium (Na), and potassium (K) contents. Crambe growth parameters decreased with the doses of biochar. Oil and macronutrient contents were in accordance to previous studies.     

Aluminum stress stimulates the accumulation of organic acids in root apices of Brachiaria species

Aluminum‐resistant Brachiaria decumbens Stapf cv. Basilisk (signalgrass) and closely related, but less resistant Brachiaria ruziziensis Germain & Evrard cv. Common (ruzigrass) both accumulated high concentrations of aluminum (Al) in roots. Approximately two thirds of the total Al was complexed by soluble low‐molecular‐weight ligands, suggesting that it had been taken up into the symplasm. We therefore investigated whether these species might employ Al‐chelating organic acids for internal detoxification of Al taken up by root apices, the primary site of Al injury. Unlike root apices of other Al‐resistant plant genotypes, which secrete organic‐acid anions to detoxify Al externally, apices of Brachiaria species accumulated organic acids within the tissue. A comparison with whole roots showed that this preference for accumulation (as opposed to secretion) was restricted to apices. Citric acid, and to a lesser extent trans‐aconitic acid, accumulated in a uniform dose‐dependent manner in root apices of both species as their Al content increased under Al‐toxic growth conditions. Their accumulation was accompanied by a stimulation of malate synthesis in Al‐resistant B. decumbens, while it occurred at the expense of malate in Al‐sensitive B. ruziziensis. These data suggest a role of organic acids in the internal detoxification of Al in root apices of both Brachiaria species, presumably contributing to their comparatively high basal level of Al resistance. Yet internal detoxification of Al by organic acids does not appear to be the principal mechanism responsible for the superior resistance of B. decumbens.     

Changes in color and odorant compounds during oxidative aging of Pedro Ximenez sweet wines

Pedro Ximenez sweet wines obtained following the typical criaderas and solera method for sherry wines and subjected to oxidative aging for 0, 1.3, 4.2, 7.0, or 11.5 years were studied in terms of color and aroma fraction by using the CIELab method and gas chromatography, respectively. The parameters defining the CIELab color space (a*, b*, and L*) were subjected to a multiple-range test (p<0.05) that allowed discrimination of the five wine aging levels studied into five uniform groups according to aging time. The aroma fraction was found to include 15 active odorant compounds with OAV > 1 that enriched the wines with fruity, fatty, floral, and balsamic notes during the aging process. The changes in color parameters and active odorants were not linearly related to aging time, being especially marked during the first 1.3 years and then less substantial up to the 7 years, the oldest wines exhibiting sensorial properties markedly departing from all others. For the wines aged over 1.3 years (minimum aging), 2,3-butanedione, linalool, and decanal can be used as reliable fingerprints of the older wines' quality.     

Petiole N,P, K Concentrations and Yield of the Potato Cultivar Molli from Certified Organic Amendments and Fertilizer Formulations

This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO₃-N) and ammonium (NH₄-N) from each amendment averaged 115 kg N ha^?1 at application and 25 kg N ha^?1 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg^?1, 4 wk after emergence to 3,000 mg N kg^?1 prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg^?1, 10,000 mg K kg^?1, and 2,000 mg S kg^?1 tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha^?1. This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments.     

Lesion size as a criterion for screening oat genotypes for resistance to leaf spot

In Brazil, increased leaf spot disease (Pyrenophora chaetomioides Speg.) frequency and intensity on cultivated spring oat (Avena sativa) requires that plant pathologists and breeders rapidly identify oat genotypes with greater resistance. Criteria are needed to compare and evaluate oat genotypes to screen large numbers of lines, quantification of resistance components under controlled conditions allowing year-long screening and the rejection of susceptible lines before lengthy field trials. There is a need to determine which resistance components are associated with leaf spot intensity in the field, as estimated from the area under the disease progress curve (AUDPC). We assessed various oat P. chaetomioides resistance components under controlled conditions in seedlings of 26 oat genotypes chosen from recommended varieties and elite breeding lines to determine the association of resistance components with the AUDPC, obtained by evaluating each genotype in the field. The resistance components estimated were: initial lesion size (ILS) and final lesion size (FLS); rate of lesion expansion (r); and area under the normalized and corrected lesion expansion curve (AULECc). All correlations were positive and significant at p?=?0.01 and were distributed into moderate (0.5?<?r?<?0.8) and strong (0.8????r?<?1) correlation classes. The strongest average correlations occurred with the AULECc (0.827), ILS (0.801) and FLS (0.801) components. These results indicate which components may be useful in resistance screening, with FLS possibly being the most useful criterion because it is less laborious to obtain and speeds up the selection process for leaf spot resistance.