Molecular and experimental evidence of multi-resistance of <Emphasis Type="Italic">Cercospora beticola</Emphasis> field populations to MBC,DMI and QoI fungicides

Binucleate Rhizoctonia (BNR) spp. isolates were collected from taro (Colocasia esculenta (L.) Schott) and ginger (Zingiber officinale (Willd.) Roscoe) (Yunnanxiaojiang cv.) in Yunnan province. These Yunnan (YN) isolates did not anastomose with any of the tester isolates of the known AGs of binucleate Rhizoctonia spp. The growth of YN cultures on PDA was appressed, mealy and matlike after 4 days of incubation, then turned white brown, producing brown to dark brown, irregularly shaped sclerotia were embedded in the PDA medium after 14 days. All attempts to induce basidiospore production were unsuccessful, but the length and sequence of the internal transcribed spacer (ITS1 + 5.8S rDNA + ITS2) regions of 5.8S rDNA from the YN isolates were identical in length and sequence to isolates of all the other AGs of binucleate Rhizoctonia /Ceratobasidium spp. The sequences of 5.8S rDNA-ITS from the YN isolates were unique among AGs of BNR. The YN isolates had sequence similarities of 94% with isolates of AG Fb and P, 93% with AG E, 91% with AG R, 79–94% with AG S, and 74–87% with AG A, Ba, Bb, Bo, C, DI, DII, DIII, Fa, G, H, I, K, L, O, and Q. Four isolates of AG YN caused minor virulence (lesions ≦1mm²⁾ to ginger or taro in growth chamber studies. It was concluded that the YN isolates belong to a new anastomosis group AG-V of the Ceratobasidium spp..     

Klimawandel als neue Herausforderung für die Modellierung von Pflanzen und Schaderregern – eine kritische Betrachtung

Pests (weeds, insect pests and plant pathogens) represent a major constraint to crop yield even under current climate conditions. How is climate change going to influence pests and damage caused by them? Unfortunately, it is impossible to conduct holistic and multiple experiments which cover all possible combinations of soil, climate, plants, pests and all interactions among these components. Thus models have to be used to simulate the impacts of climate change to increase scientific understanding. This literature survey summarizes knowledge about known pest and crop models concerning the different approaches for modelling, the spatial and temporal scales of models, uncertainties resulting from work with chaotic systems and the quality of data used in models, discussing 13 critical points, which are describing problems, which have to be resolved, but give also some hints for developing new strategies for modelling and for improving models that are currently used. The problems most difficult to resolve are the impossibility to predict changes of pests themselves, the insufficient representation of the complexities of the relations in the system “climate-plant-pest-soil-socio-economic implications”, still too large uncertainties of climate and crop models, still too large spatial and temporal scales of used climate models and missing important physiological processes, like compensation and stimulation responses in crop models. These processes are the causes for changes in function norms and norms of responses to the environment of the new system “diseased plant”.     

A comparative study of above- and below-ground parameters of healthy and declining young Norway spruce trees in a mountain area affected by air pollution

The aim of this study was to characterize possible connections between above- and below-ground parameters and the decline of Norway spruce trees in the Jeseníky Mountains of the Czech Republic – an area affected both by long-term air pollution and subjected to liming. A part of this study was dedicated to soil analysis, which showed considerable changes in the soil environment and highlighted particularly high concentrations of magnesium and calcium, exceeding optimal limits by as much as 8 and 13 times, respectively. Our results suggest that the decline of evaluated trees is primarily connected to root system development, as we found no differences between evaluated above-ground parameters for either healthy or declining trees. Tree decline related directly to low numbers of skeletal roots, root origin and higher maximal angles between skeletal roots. Declining trees had on average five skeletal roots with maximal angles between them of 173^o, indicating poor mechanical stability. Regardless of tree vitality, 93% of all examined root systems were restricted to upper humus horizons with an average rooting depth of 10.2?cm. All evaluated trees showed severe root deformation into tangle, which suggests crucial influence of artificial planting on the architectural development of root systems.     

Influence of Rhizon MOM suction cup and Triticum aestivum L. on the concentration of organic and inorganic anions in soil solution

Journal of Soils and Sediments - Rhizon suction cups are widely used for soil water sampling. However, available literature about the variability and stability of organic and inorganic anions in...     

Methane cycling in a drained wetland soil profile

Purpose

Peatlands have an important role in methane cycling in the natural environment. Methane emissions as a result of methanogenesis and methanotrophy in soil are affected by several environmental factors such as temperature, oxygen and groundwater level. The objective of this study was to analyse methane cycling as a function of soil depth.

Materials and methods

In this study, methane cycling and soil organic matter mineralization were investigated in a drained fen grassland area of Ljubljana marsh, Slovenia that has been subjected to reclamation strategies for several centuries. Potential mineralization, methane production and methane oxidation rates were measured in slurry incubation experiments with soil samples from 10 sampling depths of a 1-m profile. In addition, the extent of iron reduction in the soil was determined.

Results and discussion

The potential for methane production was low in the investigated soil profile, even in constantly flooded layers below the water table fluctuations. During anaerobic incubations, the highest accumulated concentrations and production rates of methane were observed in the upper 10-cm layer and the lowest in deeper soil layers, indicating that plant exudates are the main source of energy for heterotrophic soil microbes and that methanogenesis in deeper layers is limited by the availability of appropriate organic substrates. Methane oxidation was on the other hand active throughout the soil profile, suggesting that the potentially active methane oxidizing community is present despite low methane production. The highest abundance and activity of methanotrophs was detected in the water table fluctuation layers.

Conclusions

Together, these findings have implications for understanding the biogeochemical function of drained peat soils and emphasize the influence of drainage on quality of soil organic matter and consequently on methane production even in flooded soils.

     

Histological and immunohistochemical characteristics of cerebral amyloid angiopathy in elderly dogs

Background: Cerebral amyloid angiopathy (CAA) is a disorder characterized by amyloid deposition in the wall of cerebral blood vessels. The deposits of amyloid occur frequently in the blood vessels of the frontal, parietal and occipital cortex.

Objective: To examine the characteristics of CAA classified according to the Vonsattel scale in elderly dogs histologically and immunohistochemically as well as the semi-quantitative evaluation of the amyloid deposits in the different segments of the brain.

Animals and methods: The brains of 36 dogs of different breeds and sexes, which had been routinely necropsied, were used and divided into two groups: dogs from 1 to 5 and 10 to 18 years old. The tissue sections were stained by hematoxylin–eosin, Congo red and immunohistochemically.

Results: Amyloid was accumulated in the wall of cerebral blood vessels in 70% of dogs over the age of 10 years predominantly in the frontal cortex. CAA was demonstrated in elderly dogs as follows: in the frontal cortex (n = 19 or 63%), the parietal cortex (n = 12 or 40%), the hippocampus (40%) and the cerebellum (n = 5 or 17%). The deposits of amyloid in the wall of blood vessels detected by Congo red staining were also Aβ1-14 and Aβ1-42 immunohistochemically positive. Most commonly, the amyloid deposits affected a moderate number of blood vessels. The accumulation of amyloid was immunohistochemically revealed in the blood vessel walls as well as in the senile plaques and neurons.

Conclusion: The amount of amyloid in the arterial walls increased with age in dogs, whereas the amyloid accumulated in plaques was Congo red negative.     

Effect of <Emphasis Type="Italic">Meloidogyne ethiopica</Emphasis> parasitism on water management and physiological stress in tomato

Root-knot nematodes (RKN) are obligate endoparasites that severely damage the host root system. Nutrient and water uptake are substantially reduced in infested plants, resulting into altered physiological processes and reduced plant growth. The effect of nematode infestation on the morphological changes of roots and subsequent physiological plant responses of infested tomatoes with the RKN Meloidogyne ethiopica was studied in a pot experiment. Plants were infested with two inoculum densities (10 or 50 eggs per cm³ substrate) and its effect was evaluated 74 and 102 days post inoculation (DPI). Morphological changes and root growth was determined by analysing scanned images of the whole root system. Nematode infestation reduced the portion of fine roots and increased that of coarse roots due to gall formation. Fine roots of non-infested control plants represented around 51% of the area of the whole root system at 74 and 102 DPI. In comparison to controls, plants inoculated with low and high nematode density had 2.1 and 3.2-times lower surface area of fine roots at 102 DPI. Root analyses revealed that plants had a very limited ability to mitigate the effects of the root-knot nematodes infestation by altering root growth. Root galls had a major influence on the hydraulic conductivity of the root system, which was significantly reduced. The low leaf water potential of infested plants coincided with decreased stomatal conductivity, transpiration and photosynthesis. The latter two were reduced by 60–70% when compared to non-infested control plants.     

β-aminobutyric acid protects <Emphasis Type="Italic">Brassica napus</Emphasis> plants from infection by <Emphasis Type="Italic">Leptosphaeria maculans.</Emphasis> Resistance induction or a direct antifungal effect?

Resistance to infection in plants can be induced by treatment with various chemicals. One such compound is β-aminobutyric acid (BABA). Its positive effect on disease resistance has been noted in several pathosystems. Here we demonstrate that treatment with BABA protects Brassica napus plants from infection by the fungal pathogen Leptosphaeria maculans. Surprisingly, BABA also displayes in vitro antifungal activity against L. maculans with EC₅₀ similar to the fungicide tebuconazole. Both spore germination and hyphal growth were affected. The toxic effect can be reverted by addition of trypton to the culture medium. We hypothesised that BABA might inhibit inorganic nitrogen assimilation. Suppression of disease progression in plants and antifungal activity in vitro was weaker for α-aminobutyric acid and negligible for γ-aminobutyric acid. In contrast to a resistance inducer benzothiadiazole, the effect of BABA on disease development was nearly independent of the timing of treatment, indicating possible antifungal activity in planta. On the other hand, quantification of multiple hormones and an expression analysis have shown that treatment with BABA induces a synthesis of salicylic acid (SA) and expression of SA marker gene PR-1, but no evidence was observed for priming of SA responses to L. maculans. While we have not conclusively demonstrated how BABA suppresses the disease progression, our results do indicate that antifungal activity is another mechanism by which BABA can protect plants from infection.