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Huhnlein A.,Julius Kuhn Institute | Schubert J.,Julius Kuhn Institute | Zahn V.,Plant Protection Office | Thieme T.,BTL Bio Test Labor GmbH Sagerheide
European Journal of Plant Pathology | Year: 2016

Over the last 30 years the importance of Potato leaf roll virus (PLRV) in commercial potato and seed potato production has decreased considerably. Since PLRV is transmitted by aphids in a persistent manner it can be controlled by applying a systemic insecticide. However, the development of insecticide resistance in the main vectors of PLRV Myzus persicae, Aulacorthum solani, Rhopalosiphoninus latysiphon, Aphis fabae, A. nasturtii, A. frangulae and Macrosiphum euphorbiae, and the development of isolates of PLRV that do not induce visible symptoms in some potato cultivars may lead to a resurgence in the significance of PLRV. Isolates of this type were found repeatedly during growing-on tests in Lower Saxony, Germany. In this study we examined such a symptomless isolate. The visible symptoms induced by this isolate in different potato cultivars were compared with those induced by isolates causing typical symptoms of a PLRV infection. By using quantitative real-time PCR the quantifiable amount of viral RNA was determined. Under climate chamber conditions all the isolates tested induced similar symptoms and did not differ in viral RNA content. Complete sequences for the tested isolates were obtained and used in a phylogenetic analysis. All the PLRV isolates compared were very similar at the molecular level. Several motifs that could play a role in symptom expression were analyzed, but none of them were correlated with the absence of symptoms in potato plants during growing-on tests. The discrepancy between the observations recorded in the growing-on tests and our experiments are discussed. © 2016 Koninklijke Nederlandse Planteziektenkundige Vereniging

Drechsler N.,BTL Bio Test Labor GmbH Sagerheide | Thieme T.,BTL Bio Test Labor GmbH Sagerheide | Shepherd D.N.,University of Cape Town | Schubert J.,Julius Kuhn Institute
Journal of Plant Diseases and Protection | Year: 2014

Maize streak virus (MSV) is the cause of one of the most devastating maize diseases in Africa. It is transmitted by leafhoppers of the genus Cicadulina. Due to the changing climate it is possible that species of this genus capable of transmitting MSV will become established and spread the virus in Europe. There is no data on the level of resistance of cultivars of European maize to MSV. The susceptibility of three maize and 15 sorghum cultivars, and Miscanthus × giganteus was investigated using agroinoculation with the virus. DAS-ELISA and a newly developed real time quantitative PCR was used to determine the concentration of virus. All three cultivars of maize were susceptible to MSV administered using agroinoculation, although there were significant differences in the levels of susceptibility. The 15 culti-vars of sorghum and Miscanthus were resistant to MSV. Transmission tests using Cicadulina mbila as the vector confirmed the resistance of two of the cultivars of sorghum and Miscanthus. Agroinoculation can only be carried out under S2 biosafety conditions. Therefore, the persistence of agro-bacteria in the plants was investigated. Five weeks after agroinoculation, the bacteria were no longer found in the above-ground parts of the plants, but still persisted in the roots of some plants. Transmission tests with an indigenous species of leafhopper, Psammotettix alienus, a vector of the related geminivirus Wheat dwarf virus, revealed that this species is not capable of transmitting MSV. Virus was found only in the body of these insects and not in their heads, which is necessary for persistent transmission through salivary glands. © Eugen Ulmer KG, Stuttgart.

Schubert J.,Institute for Biosafety in Plant Biotechnology | Habekuss A.,Institute for Resistance Research and Stress Tolerance | Wu B.,Chinese Academy of Agricultural Sciences | Thieme T.,BTL Bio Test Labor GmbH Sagerheide | Wang X.,Chinese Academy of Agricultural Sciences
Virus Genes | Year: 2014

Recently, the importance of the Geminiviruses infecting cereal crops has been appreciated, and they are now being studied in detail. Barley and wheat strains of Wheat dwarf virus are recorded in most European countries. Information on complete sequences of isolates from the United Kingdom, Spain, and Austria are reported here for the first time. Analysis revealed that their sequences are very stable. Recombination between strains was recorded only for the barley strain. We identified several defective forms of the barley strain from barley and wheat, which do not influence symptom expression. Sequences of barley isolates infecting wheat were obtained that did not differ from the isolates from barley. Based on specific features of the SIR of the barley strains, it is suggested that they are assigned to one of the two proposed new clusters, A1 or A2. © Springer Science+Business Media New York 2013.

Hu Z.-Q.,Northwest University, China | Zhao H.-Y.,Northwest University, China | Thieme T.,BTL Bio Test Labor GmbH Sagerheide
Environmental Entomology | Year: 2013

The effects of enhanced UV-B radiation on the biology of green and brown morphs of Sitobion avenae (F.) (Hemiptera: Aphididae) were tested under laboratory conditions. The two S. avenae morphs were exposed directly to different doses (0, 216, 432, and 864 kJ/m2) of artificial UV-B. Under low doses of UV-B (216 kJ/m2), the nymphal development period was significantly shorter, whereas mean relative growth, total fecundity, and gross reproductive rate were significantly higher for both aphid morphs compared with those morphs under control treatments (0 kJ/m2). Under high doses of UV-B (432 kJ/m2 and/or 864 kJ/m2), the nymphal development period was significantly longer, whereas the reproductive period, postreproductive period, difference in weight, mean relative growth, and life table parameters were significantly reduced for both aphid morphs. Moreover, the nymphal development period was significantly shorter and the differences in weight, mean relative growth, total fecundity, and life table parameters were significantly higher for the brown morph under high doses of UV-B compared with the green morph. The results showed that enhanced UV-B affects the performance of the green and brown S. avenae morphs from positively to negatively. The brown morph exhibited stronger adaptability than the green morph at high doses of UV-B. © 2013 Entomological Society of America.

Gloyna K.,BTL Bio Test Labor GmbH Sagerheide | Thieme T.,BTL Bio Test Labor GmbH Sagerheide | Zellner M.,Bavarian State Research Center for Agriculture
Journal of Applied Entomology | Year: 2011

The EU policies for decreasing reliance on fossil fuels and reducing greenhouse gas emissions present challenging targets for bioenergy production. Field trials in Europe of Miscanthus×giganteus (Poales: Poaceae) over the past 20 years have shown that this plant is suitable for the production of biomass but the economic models promoting its use for this purpose often assume that controlling its pests will cost little or nothing. Laboratory experiments were conducted to determine whether this plant is suitable for the development of larvae of the western corn rootworm (WCR), Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), which is an important pest of maize. Larvae of WCR, originating from a Central and South Eastern European population, can develop on Miscanthus. © 2010 Blackwell Verlag, GmbH.

Thieme T.,BTL Bio Test Labor GmbH Sagerheide | Dixon A.F.G.,Academy of Sciences of the Czech Republic | Dixon A.F.G.,University of East Anglia
Journal of Applied Entomology | Year: 2015

Aphid taxa are characterized by a number of biological features, such as their feeding behaviour and host selection, which it is generally accepted are affected by keeping them for several generations under standard conditions in a laboratory. Analyses of three strains of the green pea aphid, Acyrthosiphon pisum (Harris, 1776), reared in culture for long periods, indicate that other characters are also affected. For example, the response of these aphids to alarm pheromone is dramatically reduced. This raises an interesting question regarding the mechanism by which it occurs and has consequences when aphids from laboratory cultures are used for studies in ecology and applied biology and especially the long-term effectiveness of crop plants genetically engineered to produce EBF as a means of controlling aphids. © 2015 Blackwell Verlag GmbH.

Huhnlein A.,Information Center and Library | Drechsler N.,BTL Bio Test Labor GmbH Sagerheide | Steinbach P.,LALLF M V | Thieme T.,BTL Bio Test Labor GmbH Sagerheide | Schubert J.,Information Center and Library
Journal of Plant Diseases and Protection | Year: 2013

Potato virus Y (PVY) is becoming increasingly important in potato growing regions worldwide. The main reason for this is an increase in the incidence of infections with recombinant forms of PVY, such as PVYNWi and PVYNTN. They are characterized by high virulence and low symptom expression, which is especially true of PVYNWi. This makes it difficult to detect infected seed potato plants during certification. In Mecklenburg-Western Pomerania (North-East Germany) in 2008 an unusually high incidence of infection with PVY was recorded in fields where seed potatoes were being grown. In this study we examined, which strains of PVY caused these infections. Furthermore, we have developed a reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) assay for direct tuber testing, which we com- pared to direct tuber testing by ELISA and growing-on tests. As a result, we recommend for direct tuber testing by RT-qPCR or ELISA. These methods are less space and time-consuming and therefore less costly alternatives to conventional ELISA testing of eye cuttings from seed potatoes. Additionally, the RT-qPCR method has a high efficacy, so that even freshly harvested non-dormant tubers can be tested, which makes testing very fast and economical. This is of special interest in cases when tubers shall be exported to the other hemisphere of the world. © Eugen Ulmer KG, Stuttgart.

Hu Z.-Q.,Northwest University, China | Zhao H.-Y.,Northwest University, China | Thieme T.,BTL Bio Test Labor GmbH Sagerheide
Insect Science | Year: 2014

Life tables of brown and green color morphs of the English grain aphid, Sitobion avenae (Fabricius) reared on barley under laboratory conditions at 20 ± 1°C, 65% ± 5% relative humidity and a photoperiod of 16 : 8 h (L : D) were compared. The plants were either: (i) infected with the Barley yellow dwarf virus (BYDV); (ii) not infected with virus but previously infested with aphids; or (iii) healthy barley plants, which were not previously infested with aphids. Generally, both color morphs of S. avenae performed significantly better when fed on BYDV-infected plants than on plants that were virus free but had either not been or had been previously infested with aphids. Furthermore, when fed on BYDV-infected plants, green S. avenae developed significantly faster and had a significantly shorter reproductive period than the brown color morph. There were no significant differences in this respect between the two color morphs of S. avenae when they were reared on virus-free plants that either had been or not been previously infested with aphids. These results indicate that barley infected with BYDV is a more favorable host plant than uninfected barley for both the color morphs of S. avenae tested, particularly the green color morph. © 2013 Institute of Zoology, Chinese Academy of Sciences.

Thieme T.,BTL Bio Test Labor GmbH Sagerheide | Gloyna K.,BTL Bio Test Labor GmbH Sagerheide | Drbal U.,BTL Bio Test Labor GmbH Sagerheide | Zellner M.,Bavarian State Research Center for Agriculture
Journal of Applied Entomology | Year: 2010

Three different bioassays were used to determine the susceptibility to the neonicotinoid Biscaya® of oilseed rape pollen beetles collected from fields in Bavaria. The one in which the test substance was applied to the inner wall of glass tubes is recommended for future studies on pollen beetles because it is not dependent on the availability of plant material and provides precise information on the amount of insecticide required per unit area. © 2009 Blackwell Verlag, GmbH.

Hu Z.-Q.,Northwest University, China | Zhao H.-Y.,Northwest University, China | Thieme T.,BTL Bio Test Labor GmbH Sagerheide
Archives of Biological Sciences | Year: 2013

UV-B induced changes in plants can influence sap-feeding insects through mechanisms that have not been studied. Herein the grain aphid, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), was monitored on barley plants under the treatments of control [0 kJ/ (m2.d)], ambient UV-B [60 kJ/ (m2.d)], and enhanced UV-B [120 kJ/ (m2.d)] irradiation. Electrical penetration graph (EPG) techniques were used to record aphid probing behaviors. Enhanced UV-B irradiated plants negatively affected probing behaviors of S. avenae compared with control plants. In particular, phloem factors that could diminish sieve element acceptance appeared to be involved, as reflected by smaller number of phloem phase, shorter phloem ingestion, and fewer aphids reaching the sustained phloem ingestion phase (E2>10min). On the other hand, factors from leaf surface, epidermis, and mesophyll cannot be excluded, as reflected by higher number of non-probing, longer non-probing and pathway phase, and later the time to first probe.

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