Evaluation of an avirulent strain ofPseudomonas solanacearum for biological control of bacterial wilt of potato

An avirulent strain ofPseudomonas solanacearum, B82, was tested for its ability to protect the potato cultivar, Ontario, from bacterial wilt caused by virulent strains of this bacterium. Strain B82 was not antagonistic to 124 virulent strains ofP. solanacearum and was not bacteriocinogenic. When potato seedpieces were soaked for 5 hr in suspensions of B82 (10⁸ to 10⁹ cfu/ml), reduction in disease severity (up to 50%) was noted in some experiments. The treated plants, grown in the greenhouse or growth room for 4–5 wk, were challenged by stem inoculation, soil drenching, or root-to-root infection with virulent strains (276 or Br5) of the bacterium. Protection was not obtained consistently, however, and much of the variability could be attributed to differences in ambient temperature and light conditions in the greenhouse between experiments. In general, high ambient temperatures and/or reduced sunlight resulted in no protection. Protection appeared to depend on the ability of strain B82 to multiply in the vascular system in the crown region and to colonize the rhizosphere of treated plants. Soil temperatures above 24 C affected the ability of strain B82 to survive in the rhizosphere. The close dependence of protection on environmental conditions suggests that this method of control may not be practical under field conditions.     

Root uptake of lipophilic zinc-rhamnolipid complexes

This study investigated the formation and plant uptake of lipophilic metal-rhamnolipid complexes. Monorhamnosyl and dirhamnosyl rhamnolipids formed lipophilic complexes with copper (Cu), manganese (Mn), and zinc (Zn). Rhamnolipids significantly increased Zn absorption by Brassica napus var. Pinnacle roots in (65)Zn-spiked ice-cold solutions, compared with ZnSO4 alone. Therefore, rhamnolipid appeared to facilitate Zn absorption via a nonmetabolically mediated pathway. Synchrotron XRF and XAS showed that Zn was present in roots as Zn-phytate-like compounds when roots were treated with Zn-free solutions, ZnSO4, or Zn-EDTA. With rhamnolipid application, Zn was predominantly found in roots as the Zn-rhamnolipid complex. When applied to a calcareous soil, rhamnolipids increased dry matter production and Zn concentrations in durum (Triticum durum L. cv. Balcali-2000) and bread wheat (Triticum aestivum L. cv. BDME-10) shoots. Rhamnolipids either increased total plant uptake of Zn from the soil or increased Zn translocation by reducing the prevalence of insoluble Zn-phytate-like compounds in roots.     

Effects of tillage and traffic on crop production in dryland farming systems: I. Evaluation of PERFECT soil-crop simulation model

Agricultural production systems are complex involving variability in climate, soil, crop, tillage management and interactions between these components. The traditional experimental approach has played an important role in studying crop production systems, but isolation of these factors in experimental studies is difficult and time consuming. Computer simulation models are useful in exploring these interactions and provide a valuable tool to test and further our understanding of the behavior of soil–crop systems without repeating experimentation.Productivity erosion and runoff functions to evaluate conservation techniques (PERFECT) is one of the soil–crop models that integrate the dynamics of soil, tillage and crop processes at a daily resolution. This study had two major objectives. The first was to calibrate the use of the PERFECT soil–crop simulation model to simulate soil and crop responses to changes of traffic and tillage management. The second was to explore the interactions between traffic, tillage, soil and crop, and provide insight to the long-term effects of improved soil management and crop rotation options. This contribution covers only the first objective, and the second will be covered in a subsequent contribution.Data were obtained from field experiments on a vertisol in Southeast Queensland, Australia which had controlled traffic and tillage treatments for the previous 5 years. Input data for the simulation model included daily weather, runoff, plant available water capacity, and soil hydraulic properties, cropping systems, and traffic and tillage management. After model calibration, predicted and measured total runoffs for the 5-year period were similar. Values of root mean square error (RMSE) for daily runoff ranged from 5.7 to 9.2 mm, which were similar to those reported in literature. The model explained 75–95% of variations of daily, monthly and annual runoff, 70–84% of the variation in total available soil water, and 85% of the variation in yield. The results showed that the PERFECT daily soil–crop simulation model could be used to generate meaningful predictions of the interactions between crop, soil and water under different tillage and traffic systems.Ranking of management systems in order of decreasing merit for runoff, available soil water and crop yield was (1) controlled traffic zero tillage, (2) controlled traffic stubble mulch, (3) wheeled zero tillage, and (4) wheeled stubble mulch.     

Anaerobic biotransformation of organo-arsenical pesticides monomethylarsonic acid and dimethylarsinic acid

Monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV) are extensively utilized as pesticides, introducing large quantities of arsenic into the environment. Once released into the environment, these organo-arsenicals are subject to microbial reactions. Aerobic biodegradation of MMAV and DMAV has been evaluated, but little is known about their fate in anaerobic environments. The objective of this study was to evaluate the biotransformation of MMAV and DMAV in anaerobic sludge. Biologically mediated conversion occurred under methanogenic or sulfate-reducing conditions but not in the presence of nitrate. Monomethylarsonous acid (MMAIII) was consistently observed as an important metabolite of MMAV degradation, and it was recovered in molar yields ranging from 5 to 47%. The main biotransformation product identified from DMAV metabolism was MMAV, which was recovered in molar yields ranging from 8 to 65%. The metabolites indicate that reduction and demethylation are important steps in the anaerobic bioconversion of MMAV and DMAV, respectively.     

Mineralogy and petrology of comet 81P/Wild 2 nucleus samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk.     

The health of wild red and sika deer in Scotland: an analysis of key endoparasites and recommendations for monitoring disease

Monitoring the health of wildlife populations is important for understanding and controlling the risk of infections to livestock, humans and/or other wildlife. In this paper, we analyse the results of surveys of parasites and non-specific signs of diseases carried out on organs from 638 red and 107 sika deer culled in four regions of Scotland between 1991 and 1997. Infections of the lung by Elaphostrongylus spp. were significantly greater in red than sika deer. Older animals were more heavily infected with Elaphostrongylus spp. and Sarcocystis spp., and infections with Sarcocystis spp. tended to be heavier in more recent years. The results suggest that a combination of key indicator parasite species and non-specific signs of disease may be useful for monitoring the health of wildlife populations at a national scale. However, they also demonstrate that such monitoring needs to be long-term, carried out according to standard protocols and at an appropriate resolution to enable integration with data on other potentially influential environmental factors.     

A multiple disease test for field-based phenotyping of resistances to Fusarium head blight,yellow rust and stem rust in wheat

Wheat is affected by many diseases, in Germany eight fungal diseases are recorded during the cultivar registration process. For a commercially successful cultivar, therefore, at least moderate resistances to important diseases, like yellow rust (YR) and Fusarium head blight (FHB), are necessary. Additionally, in 2013 a regional stem rust (SR) epidemic occurred in Central Germany for the first time for decades. Our objective was to analyze the resistance of 36 commercially grown winter wheat cultivars to YR, FHB, and SR in three individual and one combined inoculation. Appreciable disease severities were achieved for YR and FHB at three to four locations in two years (= seven location × year combinations), for SR at one to two locations in two years (= three location × year combinations). Wheat cultivars showed a significant genotypic variation for all diseases with high heritabilities (0.90–0.95). Interaction between inoculation treatments (individual vs. combined) and wheat genotype was not significant for each of the three diseases. Accordingly, correlations between both inoculation treatments were very high (R²?=?0.95–0.99). Several cultivars showed multi-disease resistance (MDR) to YR, FHB, and SR. In conclusion, resistance ranking among genotypes was not changed when plants were challenged with all three pathogens together compared to factorial inoculations of only one of them. Substituting factorial inoculation trials by multi-pathogen inoculation makes it more efficient to select for MDR in practical breeding programs.     

Spatiotemporal variation in forest fire danger from 1996 to 2010 in Jilin Province,China

We evaluated the spatial and temporal patterns of forest fires in two fire seasons (March to June and September to November) from 1996 to 2010 in Jilin Province, China, using the Canadian Forest Fire Weather Index System. Fire data were obtained from the Provincial Fire Agency, and historical climate records of daily weather observations were collected from 36 weather stations in Jilin and its neighboring provinces. A linear regression model was used to analyze linear trends between climate and fire weather indices with time treated as an independent variable. Correlation analysis was used to detect correlations between fire frequency, areas burned, and fire weather indices. A thin-plate smooth spline model was used to interpolate the point data of 36 weather stations to generate a surface covering the whole province. Our analyses indicated fire frequency and areas burned were significantly correlated with fire weather indices. Overall, the Canadian Forest Fire Weather Index System appeared to be work well for determining the fire danger rating in Jilin Province. Also, our analyses indicated that in the forthcoming decades, the overall fire danger in March and April should decrease across the province, but the chance of a large fire in these months would increase. The fire danger in the fall fire season would increase in the future, and the chance of large fire would also increase. Historically, because most fires have occurred in the spring in Jilin Province, such a shift in the future fire danger between the two fire seasons would be beneficial for the province’s fire management.