Journal of Plant Diseases and Protection, 115 (3), 134–135, 2008, ISSN 1861-3829. © Eugen Ulmer KG, Stuttgart
J.Plant Dis.Protect. 3/2008
Report on the Annual Meeting of the Working Group “Nematology”
In 2008 the Working Group „Nematology“ of the German Phytomedical Society (Deutsche Phytomedizinische Gesell- schaft, DPG) met with the Working Group “Free Living Nem- atodes” from February 14 to 15, at the University of Natural Resources and Applied Life Sciences in Vienna, Austria. For the kind invitation and excellent local arrangements the orga- nizers warmly thank Prof. Florian Grundler and his team from the Department of Plant Protection. Sincere thanks are also given to Syngenta Crop Protection for sponsoring the coffee breaks and the dinner. The total attendance was 45 partici- pants from Germany, The Netherlands, Austria and Switzer- land who presented 19 oral presentations and three posters.
Presentations covered the broad field of Nematology from fundamental and applied aspects in plant nematology all the way to nematode ecology and molecular aspects of plant- nematode interactions. A complete overview of all abstracts can be viewed at the homepage of the DPG (www.phyto- medizin.org). The next joint meeting of the two working groups will be held from March 11-12, 2009 at the Landwirt- schaftskammer Nordrhein-Westfalen, Kreisstellen Aachen/
Düren/Euskirchen, Rütger-von-Scheven-Straße 44, 52349 Düren (www.landwirtschaftskammer.de/dueren). This meeting will commemorate the first reference of the beet cyst nematode Heterodera schachtii in 1859 with a special section considering actual research on H. schachtii. However, all other aspects of fundamental and applied nematology are also welcomed.
Johannes Hallmann and Peter Knuth, Working Group
“Nematology”
Liliane Rueß, Working Group “Free Living Nematodes”
Starch serves as carbohydrate storage in nematode-15 induced syncytia
J. Hofmann1, D. Szakasits1, A. Blöchl2, M. Sobczak3, S. Daxböck-Horvath1, W. Golinowski3, H. Bohlmann1, F.M.W. Grundler1
1 Institute of Plant Protection, University of Natural Resources and Applied Life Sciences, Vienna, Austria, julia.hofmann@boku.ac.at
2 Department of Chemical Ecology and Ecosystem Research, University of Vienna, Austria
3 Department of Botany, Warsaw University of Life Sciences, Poland
The plant parasitic nematode Heterodera schachtii induces specific syncytial feeding sites in the roots of Arabidopsis thaliana from where it withdraws all required nutrients.
Therefore, syncytia have to be well supplied with assimilates and generate strong sinks in the host plant’s transport system.
Import mechanisms and consequent accumulation of sucrose in syncytia were described recently. In this work, we studied the starch metabolism of syncytia. Using high-performance liquid chromatography and microscopic analyses, we demon- strated that syncytia store carbohydrates by starch accumula- tion. Further, we monitored the expression of genes involved in the starch metabolic pathway by gene chip analysis and quantitative reverse transcription-PCR. Finally, we provide functional proof of the importance of starch synthesis for nematode development using T-DNA insertion lines. We con- clude that syncytia accumulate starch as a carbohydrate buffer to compensate for changing solute uptake by the nematode and as long-term storage during juvenile development.
Occurrence of Meloidogyne enterolobii in Switzerland
S. Kiewnick1, G. Karssen2, J. Brito3, M. Oggenfuss1, J. Frey1
1 Agroscope Changins-Wädenswil ACW, Research Station ACW, Plant Protection, Schloss P.O.Box 184, CH-8820 Wädenswil, Switzerland, sebastian.kiewnick@acw.admin.ch
2 National Nematode Collection, Wageningen University, P.O. Box 8123, 6700 ES Wageningen, The Netherlands
3 Florida Department of Agriculture and Consumer Services, Division of Plant Industry, 1911 SW 34th Street,
Gainesville, FL 32608, USA
Root-knot nematodes (Meloidogyne spp.) are the economi- cally most important nematodes species in Switzerland, causing damage in greenhouse and plastic tunnel vegetable production systems. Due to the limited availability of control measures, the use of root-knot nematode resistant tomato and cucumber rootstock is the standard method to avoid yield losses caused by M. incognita, M. arenaria and M. javanica.
However, in recent years severe root galling was found on resistant rootstock of tomato and cucumber, respectively, in several greenhouses in north-east Switzerland. Based on mor- phological features the root-knot nematode species responsi- ble was tentatively identified as M. mayaguensis. This species has been identified in Africa, Central American and Caribbean countries, the United States and France. Although not listed as a quarantine nematode, it is now considered to be one of the most pathogenic root-knot nematodes known. It can over- come a number of genes that code for resistance: the Mi gene in tomato, the N gene in pepper, and others. For confirmation, reference material of M. mayaguensis populations from Florida and Brazil, respectively, were used for comparison of the sequence data of the COI, ITS and mtDNA 63bp repeat region and all sequence data confirmed the correct species identifica- tion. However, additional comparative genomic studies based on the COI (310bp) and ITS (723bp) region with type mate- rial of M. enterolobii from China revealed that the Swiss populations as well as the reference material from the United States and Brazil were 100% identical. Further studies on the isozymes esterase (EST), malate dehydrogenase (MDH) and the morphology of females and second stage juveniles con- firmed the presence of the species M. enterolobii in Switzer- land. Future studies will now focus on extending the survey on tropical root-knot nematode species in Switzerland and to conduct more detailed comparative genomic studies to deter- mine to origin of this species and how it entered Swiss green- house production systems.
Studies on the use of biofumigation in the Netherlands
G. Korthals, J. Visser, J. Lamers, L. Molendjik
Applied Plant Research (PPO-AGV), Wageningen University and Reasearch, P.O. Box 430, 8200 AK Lelystad, The Nether- lands, gerard.korthals@wur.nl
This research project concentrates on biofumigation, as an alternative for chemical soil disinfestation against soil-borne pathogens like nematodes and fungi. Biofumigation is a new technique, by growing specific (green manure) crops (mainly crucifers) and incorporating these crops into the soil. By incor- porating the crops, the contents (among else some toxic break- down products) diffuse through the soil and can help to improve
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soil health. Within this project 16 different crops were tested under field conditions. The impact of the crops on nematodes (Pratylenchus penetrans), fungi (Verticilium dahliae) as well as the cash crop (Potatoes) grown afterwards were tested in a ran- domized block design. Till now it seems that most crops can be seen as a host plant for nematodes, and that the supposed pop- ulation decrease due to the biofumigation effect does not com- pensate this negative effect. However, on the quantity and qual- ity of the potatoes, there was an overall positive effect of most biofumigation crops. If the biofumigation crops and the tech- niques to grow and to incorporate them can be improved, bio- fumigation might be a new alternative to improve soil health.
Development of the wilting symptoms in pine seedlings inoculated with Bursaphelenchus vallesianus and B. mucronatus in comparison to B. xylophilus
J. Polomski
WSL, Ecological Genetic and Evolution, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland, janina.polomski@wsl.ch Pathogenic potential of the sapwood nematodes of the genus Bursaphelenchus has been rarely investigated, except for B. xylophilus being a dangerous quarantine pathogen on various pine species. Only B. xylophilus has clearly been proven to damage or kill adult trees in forests. However, an inoculation experiment of pine seedlings in greenhouse showed a highly pathogenic potential of B. mucronatus and B. vallesianus isolat- ed from dying pines in Switzerland. The external and internal disease symptoms caused by the two species followed a pat- tern similar to that described for B. xylophilus. This indicates similar mechanisms of the wilting processes for the pathogen- ic Bursaphelenchus species. Necrosis of the epithelial cells of resin canals and parenchyma cells of rays were the first symp- toms observed. Needle discoloration was delayed by few days to the internal symptoms and increased dramatically during the advanced stage of disease. The pathogenic potential of nema- todes strongly correlated with high temperature and water stress. However, to date little is known about the mechanisms responsible for the strong differences in the pathogenicity poten- tial between B. xylophilus and other Bursaphelenchus species.
Heterodera schachtii triggers neo-morphogenesis in Arabidopsis roots
D. Szakasits1, P. Heinen2, D. Kreil3, J. Hofmann1, K. Wieczorek1, F. Grundler1, H. Bohlmann1
1 Institute of Plant Protection, Department of Applied Plant Sciences and Plant Biotechnology, University of Natural Resources and Applied Life Sciences, Vienna, Austria, dagmar.szakasits@boku.ac.at
2 Institute of Plant Protection, Department of Applied Plant Sciences and Plant Biotechnology, University of Natural Resources and Applied Life Sciences, Vienna, Austria
3 WWTF Chair of Bioinformatics, Department of Biotechnology, University of Natural Resources and Applied Life Sciences, Vienna, Austria
The cyst nematode Heterodera schachtii is a biotrophic plant parasite which can cause significant economic losses on sugar beet but can also complete his life cycle on a variety of other plants including Arabidopsis. Juveniles invade the roots of host plants and induce a syncytium on which the nematode feeds throughout his life. The syncytium develops from a single cell inside the central cylinder through incorporation of neighbouring cells. How the induction and the development of the syncytium is achieved is unknown. We have studied the transcriptome of syncytia induced by Heterodera schachtii in Arabidopsis roots. Pure material from syncytia was obtained through microaspiration and used for RNA isolation. This RNA was amplified, labelled, and used for the hybridization of Affymetrix GeneChips. Our results show that a variety of genes is up- or down-regulated in syncytia. Results have been validated for selected genes by real time PCR and in situ RT-PCR. In addition, promoter::GUS lines are being prepared.
Genes which are strongly upregulated in syncytia are not only of scientific interest but may also be used as targets for appli- cations to engineer nematode-resistant plants. Closer inspec- tion of the up-regulated genes revealed, that different path- ways for genes that are normally specific for certain tissues other than roots, are induced in the syncytium. A principal component analysis of available transcriptome data has shown that syncytia have more in common with seeds and pollen than with roots.
