Phytotoxin produced by the netted scab pathogen, <Emphasis Type="Italic">Streptomyces turgidiscabies</Emphasis> strain 65, isolated in Sweden

Streptomyces spp. are a highly diverse group of bacteria most of which are soil-inhabiting saprophytes. A few are plant pathogens that produce a family of phytotoxins called thaxtomins and cause significant economic losses, e.g., by reducing the marketability of potato tubers (Solanum tuberosum). In northern Europe, S. scabies, S. turgidiscabies and S. europaeiscabiei are the most common plant pathogenic species. In this study, a Streptomyces strain isolated from a netted scab lesion on a tuber of potato cv. Bintje in northern Sweden was identified as S. turgidiscabies but was found to differ in the genomic region carrying genes required for thaxtomin biosynthesis. Our results showed that the strain did not produce thaxtomin but rather phytotoxin fridamycin E, which is an anthraquinone novel to plant pathogenic Streptomyces spp. Fridamycin E was shown to reduce or inhibit sprouting of potato microtubers in vitro. While fridamycin E is known to have antibiotic activity against Gram-positive bacteria, the inhibitory activity of fridamycin E on plant growth is a novel finding.     

DNA Quantity and Quality in Remnants of Traffic-Killed Specimens of an Endangered Longhorn Beetle: A Comparison of Different Methods

The sampling of living insects should be avoided in highly endangered species when the sampling would further increase the risk of population extinction. Nonlethal sampling (wing clips or leg removals) can be an alternative to obtain DNA of individuals for population genetic studies. However, nonlethal sampling may not be possible for all insect species. We examined whether remnants of traffic-killed specimens of the endangered and protected flighless longhorn beetle Iberodorcadion fuliginator (L., 1758) can be used as a resource for population genetic analyses. Using insect fragments of traffic-killed specimens collected over 15 yr, we determined the most efficient DNA extraction method in relation to the state of the specimens (crushed, fragment, or intact), preservation (dried, airtight, or in ethanol), storage duration, and weight of the sample by assessing the quantity and quality of genomic DNA. A modified cetyltrimethyl ammonium bromide method provided the highest recovery rate of genomic DNA and the largest yield and highest quality of DNA. We further used traffic-killed specimens to evaluate two DNA amplification techniques (quantitative polymerase chain reaction [qPCR] and microsatellites). Both qPCR and microsatellites revealed successful DNA amplification in all degraded specimens or beetle fragments examined. However, relative qPCR concentration and peak height of microsatellites were affected by the state of specimen and storage duration but not by specimen weight. Our investigation demonstrates that degraded remnants of traffic-killed beetle specimens can serve as a source of high-quality genomic DNA, which allows to address conservation genetic issues.     

Nitrogen yield and nitrogen fixation of winter faba beans

Introducing autumn-sown legumes into Central European farming systems could be beneficial for addressing two challenges for European agriculture, i.e., the substantial deficit of protein sources for livestock and expected changes in agroclimatic conditions. Therefore, a two-year field experiment was conucted under Pannonian climate conditions in eastern Austria to assess nitrogen (N) yield and N fixation of several winter faba bean varieties from different European countries as compared to a spring faba bean. Winter wheat was used as a reference crop for estimating atmospheric N fixation. Winter faba beans were susceptible to frost damage especially in the harder of the two winters. Winter faba bean varieties could not achieve a higher grain yield and a higher grain N yield than the spring faba bean but had a higher grain N concentration (except for one variety). Grain yield and grain N yield of faba beans were severely impaired by drought in one year (with a mean of varieties of 8.3 g N m^?2, winter wheat: 6.4 g N m^?2); in the other year, grain N yield of faba beans considerably surpassed that of winter wheat (with a mean of varieties of 21.5 g N m^?2, winter wheat: 8.8 g N m^?2). After harvest, faba beans left higher nitrate residues in the soil, especially in the subsoil, and higher amounts of N in above-ground residues compared to winter wheat. Faba beans showed high N fixation under optimum conditions (with a mean of varieties of 21.9 g N m^?2) whereas drought considerably impaired N fixation (with a mean of varieties of 6.3 g N m^?2; with no differences between autumn- and spring-sown faba beans). In conclusion, growing winter faba bean varieties in eastern Austria did not result in higher grain yield, grain N yield, and N fixation compared to growing a spring faba bean.     

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...     

Zur bildlichen Darstellung der gemeinsamen Sehnenscheide des M. flexor hallucis longus und des M, tibialis caudalis beim Pferd

The possibilities for imaging soft tissue structures, especially fluid-filled cavities such as articulations, bursae or tendon sheaths, have been improved markedly by sonography in recent years. Ultrasonic examinations were performed on the common tendon sheath of the musculus flexor hallucis longus and the musculus tibialis caudalis, from the medioplantar aspect of the tarsus, in 12 sound adult draft- and warm blood horses, and in 5 animals with a distended common sheath. The diagnostic precision of the sonographic examination of the tendon sheath is excellent and is superior to conventional radiography. A nuclear magnetic resonance tomogram of an isolated equine tarsus is presented for comparison method.     

Sensing of tomato plant response to hypoxia in the root environment

A severe drawback in hydroponic production systems and irrigated field cultivation arises due to the risk of hypoxia, provoked by water logging in the root environment. The effects of hypoxia become temporarily visible when plants are irreversibly damaged. For this reason, non-invasive methods are required for detecting hypoxia in good time. In five experiments, tomato plants at two stages of development were grown in containers in aerated nutrient solution. Aeration was interrupted to trigger hypoxic conditions in the root environment. Whereas young plants were able to adapt to hypoxia in the root environment and survived, mature plants wilted two days after aeration interruption and died rapidly. A decrease in leaf photosynthesis, leaf transpiration rates and efficiency of the photosystem II was observed in older plants, while leaf diffuse reflectance changed slowly. On the other hand, if young plants were able to adapt to hypoxia in the root environment and survived, no clear reduction of leaf photosynthesis and the efficiency of the photosystem II arose, although the dry matter growth was decreased by 50%. Changes in leaf colour and reflectance spectra occurred. The latter indicated changes in the profile of the carotenoids. The ratio of intensities at 550 and 455 nm in particular provided a sensitive and diagnostic parameter for hypoxia in the root zone of adapted plants which, nevertheless, displayed severe growth limitation.     

Intensive recreational activities in suburban forests: A method to quantify the reduction in timber value

Central European forests are generally multifunctional; the same forest areas are used for timber production and recreation. In frequently visited areas damage to trees can be observed. We developed a method to estimate the actual reduction in timber value due to recreation-induced damage. The method was tested in two suburban (oak–hornbeam and beech) forests sustainably maintained by a selective management system and with free access in northwestern Switzerland. Considering the total forest areas, 9.4% of oak trees and 23.0% of beech trees were damaged by recreational activities. The resulting reduction in timber value averaged 19 and 53 € ha^?1 a^?1 in the two forests. The annual reduction in timber value due to recreation-induced damage can account for up to 16% of the total proceeds. The monetary benefits of forest recreation in these areas, however, by far exceed the damage to trees.     

Einfluss verschiedener Bodenentseuchungsmaßnahmen auf das Unkrautsamenpotenzial sowie auf mikrobielle Aktivitäten im Boden

In autumn soil from the upper layer of a long-term weed nursery was sampled. This soil was fumigated with “Basamid Granulat” (dazomet) or treated with a steamer or remained untreated. During 19 months germinating weed seeds were counted in representative samples. Both sterilizing procedures nearly eliminated the seeds of annual weeds. Another part of the treated soil was incubated under laboratory conditions up to twelve weeks to investigate biomass-related dehydrogenase activity (DHA) and substrate-induced short-term respiration (KZA) as well as carbon mineralization (LZA), alkaline phosphatase (APA) and arylsulfatase (ASA). The steaming strongly reduced APA, ASA, DHA and KZA whereas “Basamid Granulat” mostly acted weaker. The LZA was slightly reduced by “Basamid Granulat” but slightly increased by steaming. Lucerne meal partly modified these effects. In a succeeding trial the disinfected soil was additionally treated with the herbicidal reference compound “Herbogil Liquide D” (dinoterb) after ten weeks. In the not disinfected soil the herbicide caused a dose-related inhibition of the DHA and – depending on sampling time, lucerne meal or dosage – affected the LZA. In the previously fumigated soil herbicidal effects may be modified. Overall the soil disinfection as well as the reference compound impaired the soil biocenosis.