Fungal colonization patterns in necrotic rootstocks and stem bases of dieback‐affected Fraxinus excelsior L.

European ash (Fraxinus excelsior) trees currently face the major threat of ash dieback caused by an invasive fungus, Hymenoscyphus fraxineus. Collar rots in F. excelsior have been increasingly associated with infections by this pathogen. However, the aetiology of the collar rots is still unclear and remains heavily debated. In contrast to most studies of this kind, entire rootstocks of four diseased ash trees were dug out to examine necrotic tissues in these rootstocks and stem bases in detail and to sample necrotic wood for fungal isolation. With the aid of morphological and molecular identification techniques, five to twelve fungal taxa were detected per tree. Members of the Nectriaceae family and Botryosphaeria stevensii, the causal agent of stem and branch cankers on many tree species, were frequently isolated from outer xylem. In contrast, H. fraxineus was the dominating species in interior wood layers. Microsatellite genotyping of 77 H. fraxineus isolates helped to identify up to six different genotypes per tree. The role of H. fraxineus and other isolated fungi in the aetiology of ash collar rots are discussed.     

Tree girdling provides insight on the role of labile carbon in nitrogen partitioning between soil microorganisms and adult European beech

Nitrogen (N) cycling in terrestrial ecosystems is complex since it involves the closely interwoven processes of both N uptake by plants and microbial turnover of a variety of N metabolites. Major interactions between plants and microorganisms involve competition for the same N species, provision of plant nutrients by microorganisms and labile carbon (C) supply to microorganisms by plants via root exudation. Despite these close links between microbial N metabolism and plant N uptake, only a few studies have tried to overcome isolated views of plant N acquisition or microbial N fluxes. In this study we studied competitive patterns of N fluxes in a mountainous beech forest ecosystem between both plants and microorganisms by reducing rhizodeposition by tree girdling. Besides labile C and N pools in soil, we investigated total microbial biomass in soil, microbial N turnover (N mineralization, nitrification, denitrification, microbial immobilization) as well as microbial community structure using denitrifiers and mycorrhizal fungi as model organisms for important functional groups. Furthermore, plant uptake of organic and inorganic N and N metabolite profiles in roots were determined.Surprisingly plants preferred organic N over inorganic N and nitrate (NO₃⁻) over ammonium (NH₄⁺) in all treatments. Microbial N turnover and microbial biomass were in general negatively correlated to plant N acquisition and plant N pools, thus indicating strong competition for N between plants and free living microorganisms. The abundance of the dominant mycorrhizal fungi Cenococcum geophilum was negatively correlated to total soil microbial biomass but positively correlated to glutamine uptake by beech and amino acid concentration in fine roots indicating a significant role of this mycorrhizal fungus in the acquisition of organic N by beech. Tree girdling in general resulted in a decrease of dissolved organic carbon and total microbial biomass in soil while the abundance of C. geophilum remained unaffected, and N uptake by plants was increased. Overall, the girdling-induced decline of rhizodeposition altered the competitive balance of N partitioning in favour of beech and its most abundant mycorrhizal symbiont and at the expense of heterotrophic N turnover by free living microorganisms in soil. Similar to tree girdling, drought periods followed by intensive drying/rewetting events seemed to have favoured N acquisition by plants at the expense of free living microorganisms.     

The effects of patulin from Penicillium vulpinum on seedling growth,root tip ultrastructure and glutathione content of maize

A culture of Penicillium vulpinum CM1 isolated from a soil sample cultivated with maize was examined for the production of the mycotoxins cyclopiazonic acid, griseofulvin, patulin (PAT), and roquefortine C. The fungal strain was positive for PAT- and roquefortine C–producing ability, while it showed negative producing ability for cyclopiazonic acid, and griseofulvin. Both PAT and roquefortine C toxins were tested for their inhibitory effect on the germination of maize seeds. Roquefortine C showed no phytotoxicity up to a concentration of 100 μg ml^?1. However, a notable reduction in the average values of fresh weight and length of roots and shoots was observed following application of PAT and a culture filtrate of P. vulpinum to maize seedlings. The phytotoxic effect was found to be dose-dependent. To analyse the cellular effects of PAT, maize root tips were treated with PAT at different concentrations. The higher dose of 25 μg ml^?1 exhibited morphological changes in the nature of cytoplasm and cytoplasmic organelles as was shown by transmission electron microscopy. Furthermore, an increase in the vacuolation with localized tonoplast dissolution was observed. At this concentration, there was evidence of a disruption of lipid metabolism. On the metabolic level, the phytotoxicity of PAT and the culture filtrate of P. vulpinum led to alterations in the total reduced glutathione (GSH) concentration in maize seedlings. The GSH concentrations examined in roots and shoots after PAT, fungal filtrate or fungal crude extract treatments were enhanced compared with control treatments. Findings further showed higher total GSH levels in shoots than in roots following treatments either with PAT or the fungal crude extract. The results are discussed in the context of known herbicide and metal effects on GSH synthesis and transport mechanisms.     

Antioxidant,ethylene and membrane leakage responses to powdery mildew infection of near-isogenic barley lines with various types of resistance

Leaves of powdery mildew-susceptible barley (Hordeum vulgare cv. Ingrid) and related near-isogenic lines bearing various resistance genes (Mla12, Mlg or mlo5) were inoculated with Blumeria graminis f. sp. hordei race A6. Fungal attack induced several-fold increases in ethylene emission and electrolyte leakage in leaves of susceptible Ingrid beginning 3 days after inoculation. Activities of peroxidase, superoxide dismutase, glutathione S-transferase, ascorbate peroxidase and glutathione reductase enzymes were induced markedly in susceptible leaves 5–7 days after inoculation. Similar, but less pronounced pathogen-induced changes were detected in inoculated leaves of Mla-type resistant plants that show hypersensitive cell death upon inoculation, and, to an even lesser extent, in the Mlg and mlo lines, where no visible symptoms accompanied the incompatible interaction. Glutathione content increased only in susceptible barley 7 days after inoculation. Catalase activity, total ascorbate content and redox state were not influenced by inoculation in any of the genotypes. The activity of dehydroascorbate reductase was significantly reduced 3–5 days after inoculation in the susceptible parental plants and after 5 days in Mla and Mlg lines, while it was stable in the mlo barley. Slightly elevated levels of H₂O₂ were observed in the inoculated resistant plants. In contrast, H₂O₂ content decreased in the susceptible line 7 days after pathogen attack. These data indicate that high levels of antioxidants are involved in the compatible interaction of susceptible barley and powdery mildew by protecting the pathogen from oxidative damage.     

Well-defined multispecies probiotic and enzyme combination outperforms traditional fermented probiotic applications in an intensive Pacific white shrimp,Litopenaeus vannamei (Boone, 1931), culture system

A series of treatments were designed to evaluate the efficacy of feeding commercial multispecies probiotics feeding with enzymes and fermentation process on the growth parameters and culture environment of Pacific white shrimp, Litopenaeus vannamei (Boone, 1931), in an intensive culture system. Commercial multispecies probiotics and enzymes (PEs) were continuously applied in three different doses, namely (i) 0.2, (ii) 0.4, and (iii) 0.6 mg L⁻¹ and designated as 0.2, 0.4, and 0.6 PE during the first 30 days of intensive culture of Pacific white shrimp, L. vannamei (Boone, 1931). The probiotics were continually applied every alternate day, while the enzymes were added every sixth day throughout the trial period. The PE dose for all treated tanks was increased by 0.2 ppm after 30 days of culture and another 0.2 ppm after day 60. Meanwhile, fermentation technique, which has become the common method applied in Indonesia in the control treatment, was added on the same day with the PE group with increasing dosage, following the same trend with the 0.6 PE group. Results showed that the group receiving 0.6 PE showed higher final biomass, higher mean weight, and protein retention efficiency as well as a lower feed conversion ratio compared with the control treatment. Abundance of Vibrio spp. remained below 10³ cfu mL⁻¹ throughout the trial. Water quality indicators TAN, NO₂ N and NO₃ N peaked in weeks 3–5 and then declined after that until the end of the culture period in all tanks. This decline was significantly faster in PE-treated tanks. Multispecies PEs have potential applications in controlling Vibrio spp., maintaining proper water quality condition, and enhancing the growth of shrimp in intensive culture system.     

Control of root zone pH is not effective in preventing Pythium aphanidermatum disease in cucumber

Journal of Plant Diseases and Protection - Pythium aphanidermatum is the most wide-spread root pathogen in greenhouse cucumber. Although environmental condi-tions are known to affect the disease...     

Continuous and pulse‐feeding application of multispecies probiotic bacteria in whiteleg shrimp,Litopenaeus vannamei

Probiotic bacteria are known to support the gut health of shrimp and thereby improve performance and production efficiency. Among other factors, the timing of probiotic application is of importance. Thus, this experiment (12‐week feeding trial followed by intramuscular Vibrio challenge) aimed to compare the effects of a multispecies probiotic feed supplement (AquaStar® Growout, 3 g/kg feed) in a continuous application with three different alternating application protocols on growth performance and immune parameters in whiteleg shrimp, Litopenaeus vannamei. Juvenile shrimp were stocked in a recirculating aquaculture system at a density of 15 shrimp/100 L and were fed an appropriate commercial diet throughout the whole trial. Tanks were randomly assigned to the treatments, and shrimp were fed one of the following five experimental treatments: T1: no probiotics (control), T2: probiotics continuously, T3: alternating 1 week probiotics, 1 week control, T4: alternating 2 weeks probiotics, 2 weeks control, or T5: alternating 2 weeks probiotics, 1 week control. While any AquaStar® Growout application significantly improved growth performance, only continuous application delayed mortality after the Vibrio challenge. Results suggest that the beneficial effects were most pronounced when AquaStar® Growout was fed either continuously or according to the T5 treatment.     

Amino Acid contents in raw materials can be precisely analyzed in a global network of near-infrared spectrometers: collaborative trials prove the positive effects of instrument standardization and repeatability files

Four international ring trials for NIRS amino acid analysis of feed raw materials have demonstrated for the first time that the calibrations developed by Degussa allow reliable and precise predictions of essential amino acids in up to 44 NIR spectrometers. Different standardization techniques were compared, and the effectiveness of using spectra of the host instruments as repeatability files was studied. The ultimately achieved reproducibility of 2-3% CV for almost all analyses in the network is considerably better than ring trial results for wet chemical amino acid analysis.     

Dietary intake of folate equivalents and risk of myocardial infarction in the European Prospective Investigation into Cancer and Nutrition (EPIC)--Potsdam study

OBJECTIVE: To assess the relationship between intake of dietary folate equivalents and risk of myocardial infarction in a German cohort. DESIGN: Intake of dietary folate equivalents was assessed by a validated food-frequency questionnaire. Cox proportional hazard models were used to evaluate the association between intake of dietary folate equivalents and risk of myocardial infarction. SETTING: The European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam cohort, Germany. SUBJECTS: Subjects were 22,245 apparently healthy non-users of vitamin supplements aged 35-64 years. RESULTS: During 4.6 years of follow-up, 129 incident cases of myocardial infarction were identified. Compared with intake below the median (103 microg), higher intake of dietary folate equivalents was associated with a multivariate-adjusted hazard ratio (HR) of 0.57 (95% confidence interval (CI) 0.36-0.91). The inverse association of folate intake and myocardial infarction risk was stronger in participants with an ethanol intake equal to or above the sex-specific median (HR=0.37, 95% CI 0.18-0.79) and attenuated in those with a low ethanol intake (HR=0.67, 95% CI 0.37-1.22). CONCLUSION: An increased intake of dietary folate equivalents was observed to be associated with decreased risk of myocardial infarction in a German study population, pointing towards the importance of folate intake with respect to primary prevention of myocardial infarction.