EFhd2/Swiprosin-1 is a common genetic determinator for sensation-seeking/low anxiety and alcohol addiction.

In many societies, the majority of adults regularly consume alcohol. However, only a small proportion develops alcohol addiction. Individuals at risk often show a high sensation-seeking/low-anxiety behavioural phenotype. Here we asked which role EF hand domain containing 2 (EFhd2; Swiprosin-1) plays in the control of alcohol addiction-associated behaviours. EFhd2 knockout (KO) mice drink more alcohol than controls and spontaneously escalate their consumption. This coincided with a sensation-seeking and low-anxiety phenotype. A reversal of the behavioural phenotype with ß-carboline, an anxiogenic inverse benzodiazepine receptor agonist, normalized alcohol preference in EFhd2 KO mice, demonstrating an EFhd2-driven relationship between personality traits and alcohol preference. These findings were confirmed in a human sample where we observed a positive association of the EFhd2 single-nucleotide polymorphism rs112146896 with lifetime drinking and a negative association with anxiety in healthy adolescents. The lack of EFhd2 reduced extracellular dopamine levels in the brain, but enhanced responses to alcohol. In confirmation, gene expression analysis revealed reduced tyrosine hydroxylase expression and the regulation of genes involved in cortex development, Eomes and Pax6, in EFhd2 KO cortices. These findings were corroborated in Xenopus tadpoles by EFhd2 knockdown. Magnetic resonance imaging (MRI) in mice showed that a lack of EFhd2 reduces cortical volume in adults. Moreover, human MRI confirmed the negative association between lifetime alcohol drinking and superior frontal gyrus volume. We propose that EFhd2 is a conserved resilience factor against alcohol consumption and its escalation, working through Pax6/Eomes. Reduced EFhd2 function induces high-risk personality traits of sensation-seeking/low anxiety associated with enhanced alcohol consumption, which may be related to cortex function.

THE IMPACT OF SILICON ON TRANSCRIPTS RELATED TO CUCUMBER MOSAIC VIRUS INFECTION IN CUCUMBER.

The role of soluble silicon (Si) in alleviating viral plant infections is largely unknown. In order to analyse this gap in knowledge, this study provides insights into the relative gene expression data obtained from 1) control, 2) Cucumber mosaic virus (CMV)-infected and 3) sodium silica-treated, CMV-infected Cucumis sativus line B10 tissue cultures regenerated plants. The absence or presence of CMV was determined through RT-PCR, six days' post-inoculation. qRT-PCR was performed on five selected host genes related to CMV-defence (argonaute protein, WRKY transcription factor) and replication (chaperone, heat shock cognate protein, aquaporin). Relative gene expressions from Si-treated, CMV-infected clones were not significantly different from CMV-infected clones, but they were significantly different from the control plants. The upregulation of the chaperone, and heat shock cognate genes in Si-treated clones, is associated with enhanced virus replication, while the gene expression of the transcription factor increases and is related to defence, in contrast to decreased expression in CMV-infected clones. Aquaporin gene expression was downregulated and the argonaute expression was unaffected in both Si-treated, CMV-infected as well as CMV-infected clones. Since both alleviating and supportive gene shifts are observed in Si-treated plantlets for key genes related to the virus infection examined herein, sodium silica is suggested to have a neutral and limited impact on CMV infection in cucumber cultures.

FIRST REPORT OF 'CANDIDATUS PHYTOPLASMA ULMI' IN ULMUS LAEVIS IN GERMANY.

The wall-less bacteria of the provisory taxon 'Candidatus Phytoplasma' are obligate parasites and associated to diseases in many important crops and trees worldwide. 'Ca. Phytoplasma ulmi', assigned to 16SrV-A subgroup, is a quarantine pest and described to be associated to elm phloem necrosis, leaf yellowing, stunting, witches broom and decline in various elm species. Elm yellows phytoplasmas (EY) have been reported in several European countries but not in Ulmus laevis in Germany so far. Leaf samples from European white elms (Ulmus leavis PALL.) with and without chlorotic symptoms were investigated for EYs infection in Berlin and Brandenburg, Germany, through performing diagnostic nested PCR targeting partial rRNA operon of phytoplasmas. Specific PCR-products were obtained from 30 out of 59 samples. Partial 16S-rDNA sequences were assigned to 'Ca. P. ulmi' through sequence analysis, while sequence variation was observed. This is the first report of U. laevis infected with 'Ca. P. ulmi' in Germany.

DEVELOPMENT OF AN ANNOTATION SCHEME FOR STANDARDIZED DESCRIPTION OF MATHEMATICAL MODELS IN THE FIELD OF PLANT PROTECTION.

Mathematical models on properties and behavior of harmful organisms in the food chain are an increas- ingly relevant approach of the agriculture and food industry. As a consequence, there are many efforts to develop biological models in science, economics and risk assessment nowadays. However, there is a lack of international harmonized standards on model annotation and model formats, which would be neces- sary to set up efficient tools supporting broad model application and information exchange. There are some established standards in the field of systems biology, but there is currently no corresponding provi- sion in the area of plant protection. This work therefore aimed at the development of an annotation scheme using domain-specific metadata. The proposed scheme has been validated in a prototype implementation of a web-database model repository. This prototypic community resource currently contains models on aflatoxin secreting fungal Aspergillus flavus in maize, as these models have a high relevance to food safety and economic impact. Specifically, models describing biological processes of the fungus (growth, Aflatoxin secreting), as well as dose-response- and carry over models were included. Furthermore, phenological models for maize were integrated as well. The developed annotation scheme is based on the well-established data exchange format SBML, which is broadly applied in the field of systems biology. The identified example models were annotated according to the developed scheme and entered into a Web-table (Google Sheets), which was transferred to a web based demonstrator available at https://sites.google.com/site/test782726372685/. By implementation of a software demonstrator it became clear that the proposed annotation scheme can be applied to models on plant pathogens and that broad adoption within the domain could promote communication and application of mathematical models.

First Report of European mountain ash ringspot-associated virus in Sorbus aucuparia in Norway.

In July 2012, leaf mottle and intensive chlorotic ringspots were observed on urban, forest, or roadside mountain ash trees (Sorbus aucuparia L., rowan) of different ages in Norway during visual inspection of native broadleaf forest tree species. Symptoms resembled those caused by European mountain ash ringspot-associated virus (EMARaV), the type-member of the newly established genus Emaravirus, containing segmented ss(-)RNA and infecting woody host species (2). Leaves of nine out of 30 assessed rowan trees exhibiting characteristic symptoms were sampled in the counties of Nordland and Nord-Trøndelag (between 63.511806° and 66.304680°N latitude). Three of them were infested by the potential vector the eriophyid gall mite Phytoptus pyri. EMARaV was detected from total RNA extracts of leaves by reverse transcription-PCR using virus-specific primers amplifying 300 bp of RNA2 and 204 bp of RNA3, respectively (3). PCR fragments were directly sequenced from both ends and submitted to the EMBL database (accession nos. HG428680 to 97). Sequenced fragments comprising the partial gene encoding the glycoprotein-precursor (261 nucleotides of RNA2 omitting primer sequences) obtained from the nine sampled trees showed identities of 97 to 98% to the sequence of the reference strain of EMARaV from Hamburg, Germany (database accession AY563041). Comparison of 159 nucleotides of the 3' untranslated region (3' UTR) of viral RNA3 of the nine investigated rowans in Norway exhibited higher sequence diversity on nucleotide level (up to 50 nucleotide exchanges, or 31%) as previously reported from EMARaV variants from other European countries (4). When subjected to BLASTn search through GenBank, only three partial RNA3 sequences generated in this study showed sequence identities of 96% to the reference isolate (accession DQ831831). The other six sequences revealed only 68 to 73% identity to RNA3 sequences of EMARaV variants from GenBank. This led to formation of a separate cluster in phylogenetic analysis of partial RNA3 sequences of the six EMARaV variants from Norway when compared to previously characterized strains from the Czech Republic (n = 2), Finland (n = 17), Germany (n = 1), Great Britain (n = 5), Russia (n = 3), and Sweden (n = 10). From three Norwegian samples clustering separately in the tree based on the partial 3' UTR of RNA3, the partial vRNA1 was amplified by RT-PCR using a generic primer set Motif-A-sense/Motif-C-antisense (1). Sequence analyses of these PCR fragments confirmed the viruses as members of the Emaravirus genus which were most closely related to EMARaV (data not shown). This is the first report of EMARaV in Norway infecting Sorbus aucuparia, a valuable native plant of northern Europe. The data obtained suggest a higher genetic variability of the EMARaV population in mountain ash trees in Norway than in other locations in Central and Northern Europe. However, whether the EMARaV variants identified in this study represent new strains of the virus have to be investigated in the future. References: (1) T. Elbeaino et al. J. Virol. Meth. 188:37, 2013. (2) N. Mielke-Ehret. and H. P. Mühlbach. Viruses 4:1515, 2012. (3) N. Mielke et al. For. Pathol. 38:371, 2008. (4) S. von Bargen et al. For. Pathol. 43: 429, 2013.

Survival of Alternaria alternata during anaerobic digestion of biomass in stirred tank reactors.

The survival of Alternaria alternate during anaerobic digestion was investigated in context of a joint research project. The aim of this project was to estimate the phytosanitary risk of dissemination of pathogens by returning treated biomass as organic fertilizer to arable land. The studies were carried out in lab-scale stirred tank reactors under mesophilic conditions. After insertion of infected plant material into the reactors the influence on the viability of the fungal pathogen was studied concerning exposure time, pretreatment and storage of the digestates for four weeks or six months. The results clearly showed that anaerobic digestion leads to a complete inactivation of A. alternate already after an exposure time of six hours.

Effect of composting and pasteurisation on two important quarantine pests of potato.

The effect of composting and pasteurization on the quarantine pests of potato Clavibacter michiganensis ssp. sepedonicus (Cms) and Synchytrium endobioticum (Se) were examined on an experimental scale. Composting was performed with 2-L pots and 60-L composters for two months at temperatures below 50 degrees C and for 12 and 21 days at temperatures above 65 degrees C. Pasteurization was performed via water bath at 70 degrees C for maximum 2 hours. Pathogens were introduced directly or via carriers into the processes. After composting for two months and for 12 and 21 days it was possible to isolate vital Cms cells from bioassay plants and vital resting spores of Se could be extracted from sample material. Likewise it was possible to isolate vital Cms cells and resting spores of Se after pasteurization for up to two hours. Both pests could not be killed completely during the performed processes. Further studies concerning sanitization of potato wastes are necessary.

Yield loss in susceptible cultivars of spring rapeseed due to Fusarium wilt caused by Fusarium oxysporum.

In 1999, reports of spring rapeseed plants (Brassica napus L.) exhibiting wilt symptoms were received by agricultural extension personnel from farmers near Fort Vermillion and Andrew, Alberta, Canada. Fungal colonies recovered from affected plants after surface disinfection were identified as Fusarium oxysporum by comparison of morphology on carnation leaf and potato dextrose agars with literature descriptions and reference cultures. Root-dip inoculation of young rapeseed plants with spore suspensions prepared from recovered F. oxysporum colonies resulted in rapid development of symptoms seen in the field. An initial estimate of yield loss in an affected field near Andrew was performed by removing all rapeseed plants from three 1 m2 quadrats. Each plant was evaluated according to a simple three point severity scale, and then the seed from each plant was individually threshed and weighed. Fully- and partially-wilted plants yielded 0.2 and 19.3% of asymptomatic plants, respectively. In 2000, wilt symptoms were observed at a plot research site near Ranfurly, Alberta. Disease symptoms were restricted to one B. napus cultivar, Nexera 705. A similar procedure to that used at Andrew in 1999 was applied at Ranfurly, except quadrat size was 2.5 m2, and replicated comparisons were made between Nexera 705 and an unaffected cultivar, Quantum. The average number of unaffected Quantum plants was 99.4%, while only 66.9% of Nexera 705 plants were asymptomatic. No Quantum plants were severely wilted, while 11.7% of Nexera 705 plants were wilted. Yield of Nexera 705 was 38.6% of Quantum. In 2004, the impact of fusarium wilt on yield of 6 susceptible and 9 resistant B. napus cultivars was determined at nine locations in western Canada. Cultivars were selected on the basis of survey results and agronomist's reports. Across all sites, yield of the most severely affected cultivar, 45A55, was 15.9% lower than the least severely affected cultivar 3455. At the most severely affected site, yield of the most severely affected cultivar, Bianca II, was 75.2% lower than the least severely affected cultivar, Option 501. Yield of wilt-susceptible (Canterra 1604) and resistant (Cougar CL) rapeseed was compared at a replicated large-plot (576 m2 per plot) experiment at Lavoy, Alberta in 2005. The susceptible variety was severely affected and yielded 44% of Cougar CL.

Characteristics of P2X7 receptors from human B lymphocytes expressed in Xenopus oocytes.

Human B lymphocytes express an ATP-gated ion channel (P2Z receptor), which shares similarities with the recently identified P2X7 receptor. Using gene specific primers, we have now isolated P2X7 cDNA from the total RNA of human B lymphocytes. This hP2X7 receptor subtype was expressed in Xenopus oocytes and electrophysiologically characterized. The hP2X7 receptor is similar to, but does not completely match, P2Z of human B cells. The hP2X7 receptors resemble the P2Z receptors with regard to the ATP concentration of half maximal activation, reproducibility, permeation characteristics and lack of desensitization of the ATP-evoked currents. However, in contrast to the native lymphocytic P2Z receptor, the time course of activation of hP2X7 displayed an additional linearly increasing current component. Furthermore, a second, small and slowly deactivating current component exists only in hP2X7 expressed in oocytes. The activation and deactivation kinetics as well as permeation characteristics of hP2X7 are different from rat P2X7 recently expressed in oocytes. Unlike in mammalian cells, hP2X7 expressed in Xenopus oocytes is not sufficient to induce large non-selective pores.

Platelet-activating factor (PAF)-acetylhydrolase and PAF-like compounds in the lung: effects of hyperoxia.

Platelet-activating factor (PAF)-acetylhydrolase is the enzyme modulating in tissues and biological fluids the concentration of the proinflammatory factors PAF and PAF-like oxidation products of phospholipids (PAF-like compounds). We investigated whether there is a relation between PAF-acetylhydrolase activity and the concentration of PAF-like compounds in bronchoalveolar lavage (BAL). We found that alveolar type II cells are an additional source of PAF-acetylhydrolase in BAL beside macrophages. Secretion of PAF-acetylhydrolase was stimulated by phorbol ester in alveolar type II cells but not in macrophages. Studies in BAL suggested that secreted PAF-acetylhydrolase was bound to alveolar surfactant. Exposure of rats to high oxygen concentration reduced the activity of PAF-acetylhydrolase in BAL and macrophages, but not in plasma or alveolar type II cells. In contrast, hyperoxia increased the concentration of PAF-like-compounds, lipid hydroperoxides and malonedialdehyde in plasma but not in BAL. Therefore, we conclude that neither the oxidant-induced decrease of the PAF-acetylhydrolase activity nor the direct peroxidation of surfactant lipids in the alveoli provide a likely mechanism for hyperoxia-induced lung injury. Instead, lung injury is apparently caused by lipid peroxidation in plasma rather than by high oxygen pressure in the alveoli.

Identification of activating c-kit mutations in adult-, but not in childhood-onset indolent mastocytosis: a possible explanation for divergent clinical behavior.

Mastocytosis represents a mast cell proliferative disease that generally runs a benign clinical course, with spontaneous remissions mostly by puberty in childhood-onset disease, although rare forms, particularly in adult-onset disease, can be associated with (pre)malignant hematologic disorders and very rarely present as mast cell leukemia or malignant mastocytosis. Reasons for this divergent clinical behavior of childhood- versus adult-onset disease are unknown. Recently, two activating mutations in the intracellular domain of the proto-oncogene c-kit, which encodes a tyrosine kinase receptor for the mast cell growth factor stem cell factor, have been detected in the human leukemic mast cell line HMC-1. We have therefore studied lesional skin biopsies from patients with adult- and childhood-onset indolent mastocytosis for the presence of these codon 560 and 816 mutations. C-kit coding DNA sequences were amplified and analyzed by mutation-specific restriction analyses, and mutated polymerase chain reaction products were additionally cloned and sequenced. The codon 816 mutation was found in all six samples from adult patients, but not in any of the 11 specimens from children. In addition, the codon 560 mutation could be demonstrated for the first time in indolent mastocytosis, namely in two of four specimens from adult patients, but not in those from two children. These data thus provide a possible explanation for the divergent clinical behavior of adult- versus childhood-onset indolent mastocytosis, with the first being associated with an activating mutation, possibly as part of a neoplastic process, and the latter representing most likely a reactive process of an as yet unknown pathogenesis.

Dyslipemia in familial partial lipodystrophy caused by an R482W mutation in the LMNA gene.

Lipatrophic diabetes, also referred to as familial partial lipodystrophy, is a rare disease that is metabolically characterized by hypertriglyceridemia and insulin resistance. Affected patients typically present with regional loss of body fat and muscular hypertrophic appearance. Variable symptoms may comprise pancreatitis and/or eruptive xanthomas due to severe hypertriglyceridemia, acanthosis nigricans, polycystic ovaria, and carpal tunnel syndrome. Mutations within the LMNA gene on chromosome 1q21.2 were recently reported to result in the phenotype of familial partial lipodystrophy. The genetic trait is autosomal dominant. We identified a family with partial lipodystrophy carrying the R482W (Arg(482)Trp) missense mutation within LMNA. Here we present the lipoprotein characteristics in this family in detail. Clinically, the loss of sc fat and muscular hypertrophy especially of the lower extremities started as early as in childhood. Acanthosis and severe hypertriglyceridemia developed later in life, followed by diabetes. The characterization of the lipoprotein subfractions revealed that affected children present with hyperlipidemia. The presence and severity of hyperlipidemia seem to be influenced by age, apolipoprotein E genotype, and the coexistence of diabetes mellitus. In conclusion, dyslipemia is an early and prominent feature in the presented lipodystrophic family carrying the R482W mutation within LMNA.

Delayed low density lipoprotein (LDL) catabolism despite a functional intact LDL-apolipoprotein B particle and LDL-receptor in a subject with clinical homozygous familial hypercholesterolemia.

We identified a 38-yr-old male patient with the clinical expression of homozygous familial hypercholesterolemia presenting as severe coronary artery disease, tendon and skin xanthomas, arcus lipoides, and joint pain. The genetic trait seems to be autosomal recessive. Interestingly, serum concentrations of cholesterol responded well to diet and statins. We had no evidence of an abnormal low density lipoprotein (LDL)-apolipoprotein B (apoB) particle, which was isolated from the patient using the U937 proliferation assay as a functional test of the LDL-binding capacity. The apoB 3500 and apoB 3531 defects were ruled out by PCR. In addition, we found no evidence for a defect within the LDL-receptor by skin fibroblast analysis, linkage analysis, single-strand conformational polymorphism and Southern blot screening across the entire LDL-receptor gene. The in vivo kinetics of radioiodinated LDL-apoB were evaluated in the proband and three normal controls, subsequently. The LDL-apoB isolated from the patient showed a normal catabolism, confirming an intact LDL particle. In contrast the fractional catabolic rate (d-1) of autologous LDL in the subject and the normal controls revealed a remarkable delayed catabolism of the patient's LDL (0.15 vs. 0.33-0.43 d-1). In addition, the elevation of LDL-cholesterol in the patient resulted from an increased production rate with 22.8 mg/kg per day vs. 12.7-15.7 mg/kg per day. These data indicate that there is another catabolic defect beyond the apoB and LDL-receptor gene causing familial hypercholesterolemia.

Antagonism by the suramin analogue NF279 on human P2X(1) and P2X(7) receptors.

The effect of the suramin analogue 8,8'-(carbonylbis(imino-4, 1-phenylenecarbonylimino-4,1-phenylenecarbonylimino))bis(1,3 , 5-naphthalenetrisulfonic acid) (NF279) was analyzed on human P2X(1) and P2X(7) receptor subtypes (human P2X(1) and human P2X(7)) heterologously expressed in Xenopus oocytes using the two-microelectrode voltage-clamp technique. At activating ATP concentrations of 1 microM (human P2X(1)) and 10 microM ATP (human P2X(7)), IC(50) values of 0.05 microM and 2.8 microM were found for human P2X(1) and human P2X(7) receptors, respectively. An increase in the activating [ATP] shifted the NF279 concentration-inhibition curve rightwards for both receptors. NF279 slowed the activation of both human P2X(1) and human P2X(7) as well as the desensitization of human P2X(1). The data support a model in which desensitization of P2X(1) is dependent on preceding activation of these P2X receptors. It is concluded that NF279 acts as a competitive antagonist with much higher potency at human P2X(1) than at P2X(7) receptors. NF279 may hence be suited to discriminate between both receptors in native tissues.

Histological demonstration of voltage dependent calcium channels on calcitonin gene-related peptide-immunoreactive nerve fibres in the mouse knee joint.

The afferent (excitability) and efferent functions (release of neuropeptides) of primary afferent nerve fibres are based on Ca(2+)-influx. The aim of the present study was to examine the presence of L- and N-type Ca(2+)-channels at sensory nerve fibres in the mouse knee joint capsule. Specific fluorescent labelled channel blockers and antisera against these channel subtypes were combined with an immunohistochemical staining for calcitonin gene-related peptide (CGRP), a neuropeptide that is widely distributed in primary afferents. There was a nearly complete colocalisation of CGRP immunoreactivity and the binding of omega-conotoxin GVIA (toxin VIA of Conus geographus or BODIPY-verapamil (BODIPY(R) FL verapamil, hydrochloride) demonstrating the presence of N-type and L-type Ca(2+)-channels, respectively. These data were further confirmed by identical results obtained after an immunohistochemical demonstration of the two channel subtypes at the peptidergic nerve fibres.

In vivo kinetics as a sensitive method for testing physiologically intact human recombinant apolipoprotein A-I: comparison of three different expression systems.

In order to assess the structural and functional integrity of recombinant human apoA-I, we expressed apoA-I using three different expression systems: Baculovirus transfected Spodoptera frugiperda (Sf9) cells, stably transfected Chinese hamster ovary (CHO) cells, and transformed Escherichia coli (E. coli). Purified apoA-I from the three expression systems was radioiodinated and their catabolism was compared in normolipemic rabbits. The kinetic turnover studies of radiolabelled apoA-I in normolipemic rabbits revealed that highly purified recombinant apoA-I had an identical decay curve compared to native apoA-I, regardless whether it was purified from Sf9 cells, CHO cells, or E. coli. We also determined the association of the three recombinant apoA-I forms with both rabbit and human HDL. All three recombinant apoA-I forms were associated with HDL2 and HDL3 after injection into the rabbits and after incubation with human serum using both a Superose 6 column separation system and density gradient ultracentrifugation. The addition of the pro-segment or the addition of methionine at the amino-terminal end of apoA-I did not alter its metabolism and association to HDL. In conclusion, all studied expression systems are capable of producing high levels of physiologically intact recombinant human apoA-I. The aminoterminal addition of the prosegment of apoA-I or methionine did not alter the in vivo metabolism of apoA-I or its association to HDL.

Differential expression of myosin heavy-chain mRNA in muscles of mastication during functional advancement of the mandible in pigs.

Surgical and orthodontic treatment of retrognathia aims to improve orofacial function by adaptation and training of muscle capacity, which is connected with a change in muscle fibre-type proportions. The aim here was to analyse the proportion of myosin-heavy chain (MyHC) gene expression in type I (slow twitch/ST) and type IIb (fast twitch/FT) fibres during sagittal advancement of the mandible by reverse transcriptase-polymerase chain reaction (RT-PCR). The experiments were carried out on 10-week-old pigs (six test animals, six controls) over a 28-day period. Six pigs were fitted with acrylic bite blocks for sagittal advancement of the mandible. Tissue was taken from seven different regions of the masseter, temporal, medial pterygoid, and geniohyoid muscles. The 84 samples were used for histological fibre differentiation with ATPase staining and for isolation of total RNA. To measure the two MyHC isoforms, RT-PCR (in a single tube reaction with MyHC I, MyHC IIb, and GAPDH primers) was used. A significant increase was registered in the percentage of ST fibres and in mRNA from MyHC I in the anterior region of the masseter and in the posterior region of the temporal muscle of the treated animals. The proportion of ST fibres to FT fibres was increased by up to 12% after functional advancement of the mandible. The histological findings corresponded with the data for fibre mRNA generated by RT-PCR.

[Embolization by the wall components after the PTA of pelvic arterial stenoses]. / Embolisation von Wandbestandteilen nach PTA von Beckenarterienstenosen.

Quality and frequency of embolisation caused by angioplasty of stenoses of iliac arteries were investigated in 50 patients. In 18% emboli were found. They mostly consisted of atheromatous material and were visible by macroscopic view in 10% of the patients. Complications caused by embolisation during angioplasty of iliac artery stenosis however are very rare.

Effectiveness of predators and parasitoids for the natural control of Diuraphis noxia (Homoptera: Aphididae) on barley in central Ethiopia.

The Russian wheat aphid, Diuraphis noxia (Kurdj.), is a serious threat for the production of barley, Hordeum vulgare L., in Ethiopia. The pest can cause up to 100% yield losses in years of heavy infestation. Natural control of D. noxia by using predators and parasitoids might be the best alternative both from economical and ecological point of view. In this regard, a field investigation was conducted during the 2001 spring cropping season at Fitche, central Ethiopia to determine abundance of D. noxia and associated natural enemies and evaluate their effectiveness as natural control agents for this pest. In addition, the data collected during the 1995-1997 spring and summer cropping seasons at Chacha was analysed and presented. There was a highly significant difference (P < 0.01) on the population density of D. noxia between spring and summer and among sampling dates. The average aphid density was 23.1 and 0.7 aphids per tiller during spring and summer, respectively. The quantitative analyses based on predator units (PU) showed a highly significant difference (P < 0.01) among the predator groups, coccinellids and syrphids being more important, however, the coccinellid beetle, Hippodamia variegata Goeze, was the dominant species from all predator species or groups. Moreover, syrphid fly larvae were the only predators consistently found feeding on aphids within D. noxia rolled leaves. The polyphagous predators: Chrysopids, spiders and staphylinids were found to have less effect on D. noxia populations. Only two primary parasitoid species were recorded both during spring and summer cropping seasons: Aphidius colemani Vier. and Aphidius spp. Of these, A. colemani was more abundant in both seasons. The rate of parasitism was also generally low during the season. In general, the population build up of these natural enemies is slow and maximum population size is reached after the aphid population peaks and the crop has already been damaged. Further extensive work is necessary to maximize the effectiveness of natural enemies against this pest.