Journal of Plant Diseases and Protection, 116 (4), 189–191, 2009, ISSN 1861-3829. © Eugen Ulmer KG, Stuttgart
J.Plant Dis.Protect. 4/2009
Report on the Annual Meeting of the Working Group Nematology
In 2009 the Working Group „Nematology“ of the German Phy- tomedical Society (Deutsche Phytomedizinische Gesellschaft, DPG) met with the Working Group “Free Living Nematodes”
from March 11 to 12, at the Landwirtschaftskammer Nordrhein- Westfalen, Kreisstellen Aachen/Düren/Euskirchen, Rütger- von-Scheven-Straße 44, 52349 Düren. For the kind invitation and excellent local arrangements the organizers warmly thank Ewald Adams and his team from the Landwirtschafts- kammer for providing the meeting facilities and the excellent service throughout the meeting. Sincere thanks are also given to the Rheinischer Rübenbauer-Verband and Pfeiffer & Lan- gen for sponsoring the lunch on March 11th. A small group of participants used the opportunity to tour the open coal mining area of Garzweiler kindly guided by Dr. Dumbeck from RWE Power AG. The total attendance of the meeting was 78 partic- ipants from Germany, The Netherlands, Austria and Switzer- land who presented 20 oral presentations and 3 posters. To commemorate the 150 year anniversary of Heterodera schachtii several presentations focused on the history, biology and control of the beet cyst nematode. However, other presen- tations covered the broad field of Nematology from funda- mental 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.phytomedizin.org).
The next joint meeting of the two working groups will be held from March 16-17, 2010 at the Staatliches Weinbauinstitut in Freiburg (www.wbi-freiburg.de). Local arrangements will be organized by Dr. Peter Knuth.
Johannes Hallmann and Peter Knuth, Working Group
“Nematology”
Liliane Rueß, Working Group “Free Living Nematodes”
The recent history of research on Heterodera schachtii
F.M.W. Grundler
Institut für Pflanzenschutz, Universität für Bodenkultur, Peter-Jordan-Strasse 82, A-1190 Wien, Austria,
grundler@boku.ac.at
Research of the recent 50 years on Heterodera schachtii can be assigned to three main research fields: control of the patho- gen in the field, breeding of resistant plants, and analysis of the interaction of the nematode with its host. As a result of the rise of organic chemistry a number of nematicidal compounds were introduced for nematode control in sugar beet after the Second World War. First, phytotoxic fluids and later plant compatible granulates were used until the early 1980 s.
Increasing awareness of environmental aspects in pest control led to a limitation and finally a ban of the application of nematicides in sugar beet. At the same time research on bio- control via antagonists and organic soil amendments has been intensified and is still important. Research on nematode resis- tance in sugar beet can be traced back to the early 1950 s, however, it took decades until a first resistant variety entered the market around 2000, quickly followed by tolerant beet varieties with an improved yield performance. In 1997, a first candidate gene supposed to confer resistance against H. schachtii was cloned. Nematode resistant catch crops entered the market in the 1980 s and are still important in controlling H. schachtii. Since the first description many eco- logical and microscopic studies have been performed to shed
light on the interaction of H. schachtii with its host. In vivo studies finally facilitated the analysis of behavioural and cellular dynamics. With the establishment of Arabidopsis thaliana as a model host molecular biology found its way into studies on the host-parasite interaction. Plant molecular and physiological responses to the infection by H. schachtii are now known in more detail and information is available on effector molecules released by the nematodes, but we are still far away from fully understanding the complex biology of H. schachtii.
Survey of poorly growing patches in potato fields by helicopter
A. van der Sommen, A.S. van Bruggen, L. den Nijs Plant Protection Service, Geertjesweg 15, P.O. Box 9102, NL-6700 HC Wageningen, The Netherlands,
l.j.m.f.den.nijs@minlnv.nl
At the end of June, potato fields (both seed and ware pota- toes) are checked for the presence of poorly growing patches by helicopter. These patches can be caused by nematodes. Soil samples were taken from these patches to check whether nematodes really caused the poor growth. The soil samples were sent to the National Reference Laboratory of the Plant Protection Service in Wageningen for analysis. The free-living nematodes and cyst nematodes were extracted from the soil using respectively the Oostenbrink and the Kort elutriator.
Identification of the nematodes was done by morphology and PCR. In 2008, onehundredtwo badly growing patches were sampled. In comparison to previous years (2007: 51, 2006:
70) this is a high number). A possible explanation might be the lack of rain in the month of May. In sixty patches, potato cyst nematodes (PCN) were found. These results are used for surveying the virulence in The Netherlands. On ten of these patches, a potato cultivar was grown with another resistance gene than the PCN species present. The beginning of the summer is not favourable for finding Trichodorids. However, in eighteen patches these nematodes were found. Remarkable is that in these eighteen patches eight different Trichodorid species were identified. In sixty-one badly growing patches Pratylenchus spp. were found. In total five different species were identified of which P. neglectus was the most abundant (forty-eight patches). The most aggressive Pratylenchus found in the survey was P. penetrans, this nematode was found in four patches. The samples were also checked for the presence of Meloidogyne spp.; in eight patches root-knot nematodes were found. The quarantine root-knot nematodes M. chit- woodi and M. fallax were detected respectively in two and one patch. These patches were all situated in areas known to be infested with these nematodes.
Effects of the Mi-1 and the N root-knot nematode resistance gene on infection and reproduction of Meloidogyne enterolobii on tomato and pepper cultivars
S. Kiewnick, M. Dessimoz, L. Franck
Agroscope Changins-Wädenswil ACW, Research Station ACW, Plant Protection and Extension Fruit and Vegetables, Schloss P.O.Box, 8820 Wädenswil, Switzerland, sebastian.kiewnick@
acw.admin.ch
190 XXX: XXX
J.Plant Dis.Protect. 4/2009 Root-knot nematodes (Meloidogyne spp.) are the most impor-
tant nematodes species in Switzerland, causing great damage especially in organic greenhouse production systems. Recent- ly, Meloidogyne enterolobii was found in greenhouses in north-east Switzerland. Based on sequence data comparison of the COI and ITS region from M. mayaguensis populations from Florida and Brazil and M. enterolobii type material from China, it could be demonstrated that the two species are iden- tical. Meloidogyne mayaguensis has been identified in Africa, Central American and Caribbean countries, the US and France and is considered highly pathogenic as it can overcome a num- ber of resistance genes. Due to the limited availability of con- trol measures in organic farming systems, the use of root-knot nematode-resistant tomato and pepper cultivars might help to mitigate yield losses caused by M. enterolobii. Therefore, the potential of M. enterolobii to reproduce on tomato and pepper cultivars carrying the Mi-1 and N gene, respectively, was in- vestigated. The Swiss M. enterolobii populations reproduced well on all root-knot nematode-resistant plant cultivars tested.
On average, the population obtained from the organic farm was more virulent, producing higher gall indices, numbers of egg masses and eggs per gram root. Reproduction factor val- ues (Pf/Pi) ranged from 12 to 109 on resistant plant cultivars and from 23 to 44 on the susceptible cultivar ‘Moneymaker’
depending on the M. enterolobii population used. The M. arenaria population used as a control reproduced only on the susceptible cv. ‘Moneymaker’ confirming that the Mi-1 and N-resistance genes were effective in these greenhouse experi- ments. Our findings confirm the ability of M. enterolobii (syn.
M. mayaguensis) to reproduce on tomato and pepper geno- types carrying the Mi-1 and N nematode-resistance gene.
However, further studies are needed to test more genotypes and to evaluate alternative control measures for their poten- tial to control M. enterolobii.
Effects of the endophytic fungus Piriformospora indica on plant growth and development of sedentary root nematodes R. Daneshkhah, V. Peharz, J. Hofmann, K. Wieczorek, F.M.W. Grundler
Institut für Pflanzenschutz, Universität für Bodenkultur, Peter-Jordan-Strasse 82, A-1190 Wien, Austria,
roshanak.daneshkhah@boku.ac.at
The endophytic fungus Piriformospora indica was first de- scribed in 1997. Experiments revealed the growth promotion effects of this Basidiomycete with different plant species, which in many aspects are similar to effects of arbuscular mycorrhizal fungi. However, in contrast to mycorrhizal fungi, this fungus can be cultured axenically. Further, enhancement of plant defence against root and shoot pathogens and increase of tolerance against high salt concentration and drought stress were found. The aim of this study was to anal- yse the effects of P. indica on growth of Arabidopsis thaliana and Solanum lycopersicum, as well as the systemic and direct effects of fungus inoculation on the infection of the cyst nem- atodes Heterodera schachtii and the root-knot nematodes Meloidogyne incognita. Infection with the fungus increased both dry and fresh weight as well as shoot growth. The vege- tation period was shortened. Reduced length and highly branched root system were observed during the co-cultivation even without direct contact of the mycelium with the root.
Fungus growth in the root led to a reduction of gall number by M. incognita in tomato plants grown in pots and cyst number as well as infection rate by H. schachtii in Arabidopsis plants grown axenically on agar. In split-root system experiments the systemic effect of fungus infection was investigated. Whereas, in case of H. schachtii (Arabidopsis-axenic culture) no effects were detected, a significant reduction of gall formation was observed with M. incognita (Arabidopsis-axenic culture).
Occurrence of the beet cyst nematode (Heterodera schachtii) in Austrian sugar beet production regions and a comparison of a susceptible and a tolerant beet variety
G. Sigl1, H. Eigner2, F. Kempl2, F.M.W. Grundler1
1 Institut für Pflanzenschutz, Universität für Bodenkultur, Peter-Jordan-Strasse 82, A-1190 Wien, Austria,
gerhard.sigl@gmx.at
2 Zuckerforschung Tulln, Josef-Reither-Str. 21-23, A 3430 Tulln, Austria
In 2008 the field infestation with Heterodera schachtii was analysed at 48 sites in the main Austrian sugar beet produc- tion regions. At all sites the susceptible variety Valentina (susc.) and the tolerant variety Pauletta (tol.) were tested. Soil samples were taken after the emergence of the cotyledons and analysed for nematode infestation with three different meth- ods (counting of cysts, counting of eggs and juveniles, and de- termination of hatched juveniles by semi-quantitative PCR).
Samples of both varieties were taken at 23 sites from plots of 2.25 m2 size in 4 replicates at the end of August. At the end of September, from the 23 sites 7 were selected and samples were taken from plots of 7.5 m2 in 4 replicates. Pi and Pf values were determined for these plots. Important yield and quality traits were analysed from all samples. Infestation was classi- fied in the following categories: no (0 juveniles/100 g soil), low (< 501 juveniles/100 g soil), medium (501 < 1001 juveniles/100 g soil), and high (> 1001 juveniles/100 g soil).
White sugar yield (WSY) (according to the “Braunschweiger Formel”) did not differ between the varieties within each infestation category, although Valentina (susc.) produced 0.77 t/ha more mean WSY without nematodes, but 1.85t/ha less mean WSY with medium infestation. Through all infesta- tion levels, the mean white sugar content of Valentina (susc.) was 0.59% significantly higher than Pauletta (tol). While the relative WSY (Valentina/Pauletta) from the 7.5 m2 plots did not differ significantly between the infestation categories, a significant decrease below 1 was found in the 2.25 m2 plots.
In general, a trend could be observed revealing Valentina to be more productive without nematode infestation and Pauletta to be advantageous with nematode infestation.
Ecology of Heterodera schachtii: The soil is a dangerous place for this plant-parasite
A. Westphal1, J. Borneman2, J.O. Becker3
1 Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Field Crops and Grassland, Toppheideweg 88, 48161 Münster, andreas.westphal@jki.bund.de
2 Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521, U.S.A.
3 Department of Nematology, University of California, Riverside, CA 92521, U.S.A.
The sugar beet cyst nematode, Heterodera schachtii is a major problem in the production of sugar beet and cruciferous vege- table crops worldwide. Since its discovery in Germany, it has spread widely and can also be found in production areas in California. At the Riverside campus of the University of Cali- fornia, a soil had been amended with sugar beet cyst nema- tode-infested soil from a nearby field station in 1975. After initial establishment of the nematode associated with severe damage to host plants, H. schachtii population densities declined after several years of monoculture with susceptible hosts of the nematode. A biologically specifically suppressive soil had developed. In greenhouse and field studies suppres- siveness was eliminated with various biocide treatments and it was transferable with small portions of soil. Nematode cysts
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that had developed in this suppressive soil transferred sup- pressiveness as well. These cysts contained a number of poten- tially nematode-parasitic fungi, including Dactylella ovipara- sitica and various Fusarium spp. The prevalence of D. ovipara- sitica in suppressive soil was demonstrated with culture-inde- pendent detection methods. Although several species of Fusarium were also present in suppressive soil-derived cysts, D. oviparasitica had the highest nematode-suppressing poten- tial when tested under greenhouse and field microplot condi- tions. Results of these investigations demonstrated the poten- tial usefulness of microorganisms that naturally reduce population densities of H. schachtii in sustainable agricultural production.
Depth distribution of plant-parasitic nematodes affects damaging potential on crops
A. Westphal1, F.A. Robinson2
1 Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Field Crops and Grassland, Toppheideweg 88, 48161 Münster, andreas.westphal@jki.bund.de
2 Texas A&M University, College Station, TX, U.S.A
Plant-parasitic nematodes are greatly dependent on the eda- phon for their life activities and the complex soil matrix has various degrees of suitability for nematodes. For example, soil temperature, moisture, and gas concentrations impact the soil environment and vary with soil depth. Biotic factors include possible parasitism by microorganisms or predatory activity of the mesofauna along with food availability and behavioral cues. The availability of root feeding sites varies greatly with depth. Perhaps because of practical considerations, soil sam- ples for predicting risk for nematode damage are typically tak- en shallow, often at plow depth. Investigations of Rotylenchu- lus reniformis have shown that this plant-parasitic nematode can occur at high population densities at various soil depths.
Under host plants, cotton or soybean, in deep-rooting soil, large populations occur far below the plow zone and are capa- ble of causing damage to the crops. Agronomic practices such as tillage and crop rotation impact the dynamics of this depth distribution. Among methods for manipulating plant-parasitic nematode populations, the use of resistant crops has particu- lar potential for reducing impacts of nematodes below the plow zone. These distribution patterns may also explain why nematicide applications to shallow soil layers often only min-
imally benefit plant growth since deeper-occurring popula- tions may damage the crop. Distribution patterns of plant-par- asitic nematodes below conventional sampling depths appear important in plant damage and merit further investigation.
Quarantine nematodes in Switzerland – current situation
R. Eder1, I. Roth1, J.E. Frey2, M. Oggenfuss2, S. Kiewnick1
1 Agroscope Changins-Wädenswil Research Station ACW, Nematology, Schloss, CH-8820 Wädenswil, Switzerland, reinhard.eder@acw.admin.ch
2 Agroscope Changins-Wädenswil Research Station ACW, Molecular Diagnostics, Schloss, CH-8820 Wädenswil, Switzerland
Root-knot nematodes (Meloidogyne spp.) are the most impor- tant group of plant-parasitic nematodes in Switzerland caus- ing significant problems in vegetable production areas. The most common root-knot nematode species is Meloidogyne hapla, followed by the tropical and subtropical species M. in- cognita, M. javanica and M. arenaria, which are found in greenhouses only. In a survey conducted in the year 2002, the quarantine nematode M. chitwoodi was found in greenhouses in Switzerland. Furthermore, surveys conducted from 2003 through 2006 revealed the presence of the closely related quarantine species M. fallax in some locations. However, these quarantine nematodes are confined to a few greenhouses only and have not yet spread further confirming that the phytosan- itary measures were successfully implemented. In the years 2006 through 2008 only M. fallax was found in samples from infested greenhouses. An intensive survey conducted in 2009 will clarify if M. chitwoodi is still present in Switzerland. In addition to the quarantine species M. chitwoodi and M. fallax, the tropical species M. enterolobii (senior synonym of M. may- aguensis), which was placed on the European and Mediterra- nean Plant Protection Organization (EPPO) alert list in 2008, was found in greenhouses in Switzerland. So far, there are only two populations present. However, the pest risk assess- ment conducted for the EPPO region in 2009 will decide whether this species will be considered as a new quarantine pest. Meloidogyne enterolobii is considered to be one of the most pathogenic and virulent species known, particularly be- cause it is able to overcome all root-knot nematode resistance genes. If this species is considered a quarantine pest, intensive surveys are needed to evaluate where in the EPPO region this species is already present.
