The Institute of Plant Pathology of Wageningen Agricultural College (‘Landbouwhogeschool’) was founded in 1918, the same year in which Academic Education in Wageningen begun. Its first director was prof.dr. H.M. Quanjer, chair holder in Plant Pathology from 1918 to 1949. In the beginning his field of study comprised the entire range of sub disciplines: Entomology, Virology, Nematology, Bacteriology and Mycology.
Over the years more and more of these sub disciplines were granted an own chair and laboratory. In 1922 prof.dr. W.K.J. Roepke was appointed as professor of Entomology (chair in the animal aspects of plant pathology). Three years later, in 1925 prof.dr. E. van Slogteren took up the study of diseases in flower bulb crops (endowed chair in the special aspects of plant pathology) and founded the Laboratory of Flower Bulb Research in Lisse (the present PPO Lisse). After World War II it was Virology’s turn. In 1950 prof.dr.ir. T.H. Thung was appointed as professor of Virology.
Under Quanjer’s successor prof.dr. A.J.P. Oort a readership ('lectoraat') in Nematology was established in 1956. The Crown appointed dr.ir. M. Oostenbrink, Head of the Nematology Section at the Netherlands Plant Protection Service, in this part-time lecturing position at the Department of Plant Pathology.
It took until 1972 before Oostenbrink’s group became an independent Department (‘vakgroep’). In 1978 -one year before his untimely death- Oostenbrink's readership was transformed into a professorate. Oostenbrink was succeeded by the first full professor in Nematology, prof.dr.ir. A.F. van der Wal, who held the chair from 1982 to 1992 On September 1st 1998 prof.dr.ir. J. Bakker, the current chair holder in Nematology, was appointed as his successor.
The Laboratory of Nematology currently houses two professors:
- prof.dr.ir. J. Bakker- Head of the Laboratory. Chair of Nematology (Physiology and Molecular Ecology of Nematodes).
- prof.dr.ir. W.H. van der Putten - Part-time professor. Endowed Chair of Functional Biodiversity (Role of Nematodes in Multitrophic Interactions)
Together with our Temporary Research Staff of Postdoctoral Fellows and PhD students, and supported by the members of our Technical Staff and a team of two Office Managers, they are responsible for our Research and Education.
In the beginning research was focused exclusively on plant parasitic nematodes. They had become a substantial problem in the intensifying Dutch agriculture. Potato cyst nematodes received the most attention (it had been the subject of Oostenbrink’s dissertation in 1950), potatoes being one of the Netherlands main agricultural export commodities. This exclusive focus on plant parasitic nematodes continued until about 1980, although with some vision foresight, a little attention had already been given to the systematics of free living nematodes.Research on the free living nematodes could develop rapidly after 1980, when the possibilities of using nematodes as bio-indicators in environmental studies became apparent. Collaboration with the Dutch National Institute for Public Health and the Environment (RIVM) from 1985 onwards led to the development of the so-called Maturity Index by dr.ir. Tom Bongers.
Expertise in nematode systematics is another historical strongpoint of our group. Over the years an immense collection of nematode species samples has been amassed and (partly) described by taxonomist drs. Piet Loof (1925). In the last few years the novel discipline of molecular systematics has become a welcome addition to classical nematode taxonomy. Our research efforts in this area, led by dr.ir. J. Helder, have resulted in a patented technique for molecular recognition of nematode species using PCR.
On January 1st 1996 the Laboratory for Monoclonal Antibodies which had been established at Wageningen Agricultural University in the mid eighties became an integral part of the Laboratory of Nematology and changed its name to Laboratory of Molecular recognition and Antibody technology. Since the late nineties, the Laboratory of Nematology has widened its scope and various exciting new research lines have been established.
One of the longstanding wishes of ecologists is to assess and quantify the biodiversity in soil ecosystems. The research group, led by dr.ir. J. Helder has made a significant effort by collecting the vast majority of the most common nematode species in Europe. Sequencing the SSU rDNA from single nematodes and phylogenetic analyses of more than 1200 SSU revealed not only novel insights in the evolutionary history of nematodes, but allowed also the identification SNPs to identify and quantify nematode species. This major breakthrough enables studying the dynamics of nematode communities with an unprecedented speed and precision and opens a completely new area of research to study the functioning of soil food webs. A key question in plant nematology is understanding the mechanisms underlying plant parasitism. The phylogenetic analysis of the 1200 SSU rDNA sequences has shown that plant parasitism has occurred at least three times independently, most likely from fungal feeders.
A major step forward was the discovery that, unlike most other animals, plant parasitic nematodes are able to synthesize a wealth of cell wall degrading and modifying enzymes. (dr.ir. G. Smant). For many years it was believed that animals are dependent on symbiotic micro-organisms to degrade plant cell walls. However, in recent period it has been shown that nematodes do not only produce cellulases, polygalacturonases, pectate lyases, but also but also expansines, until recent only thought to be present in plants.
Another remarkable finding was that plant parasitic nematodes secrete a suite of proteins that consist only of a B30.2/SPRY domain and signal peptide for secretion (SPRYSEC family). Fluorescence microscopy showed that members of this SPRYSEC family were found to interact with nucleo-cytoplasmic resistance (R) protein of the NB-LRR family (dr.ir. Goverse). One member of this SPRYSEC family was shown to suppress the defence reaction to the potato cyst nematode, instead of eliciting a defence response.
The ultimate goal is to obtain a complete understanding of the interactions between plants and pathogens. The outcome of plant-microbe interactions is governed by various biotic and abiotic factors, like temperature, nutrients, pH and soil type. As a first step towards this goal we set out a research program that takes advantage of the model organism Caenorhabditis elegans and performed genetical genomics on a recombinant inbred population in different abiotic environments and treated the expression level of each gene as a single quantitative trait.
About 59% of the trans-acting genes showed a significant eQTL-by-environment interaction and only 8% of the cis-acting genes showed such an interaction. At lower temperatures, these changes in gene expression are associated with larger adult animals in C. elegans and a detailed analysis showed that growing larger at lower temperatures- a phenomenon observed in about 98% of the organisms on earth- could be explained by a single mutation in a calpain protease. This exciting example shows that the ability to sequence and monitor thousands of genes opens ways to make links between individual genes and their role at the population level under different environmental conditions. The ultimate experiment to unravel plant-parasite interactions is to perform genetical genomics on both partners in different environmental conditions (dr. ir. J.E. Kammenga).
Around 2004, we also started a new field of research led by dr. ir. A. Schots. In the last decades industrialized countries have witnessed a dramatic increase of hyper immune diseases. The prevalence of allergies and asthma increased from less than 15% to more than 30%. Likewise the number of patients suffering from autoimmune diseases, such as type 1 diabetes, multiple sclerosis, rheumatoid arthritis and Crohn’s disease raised from 1 to 5% of the population. This immune system related disorders are associated with a modern lifestyle and the prevailing view is that the increased susceptibility to allergies and autoimmune diseases is caused by a reduced exposure to infectious nematodes and microbial pathogens (hygiene hypothesis). Through the abundant use of antibiotics, vaccines and improved hygiene in Western countries the immune system hardly faces any challenges, resulting in a weakened and imbalanced immune system. If this trend in industrialized countries continues the next thirty years at the same pace the impact on society will be catastrophic. Livestock animals suffer from comparable diseases. The objective of this research line is to identify the mechanisms that may explain the hygiene hypothesis.
In addition, the Laboratory of Nematology, works in close collaboration with prof. dr. W. van de Putten and dr.ir M. Bezemer. Both are prominent ecologists with a strong reputation in functional ecology. The rapid ongoing loss of biodiversity gives rise to many questions about the functionality of multi-species communities. The prevailing hypothesis was that there is a positive correlation between species diversity and ecosystem stability. We showed that diverse systems can be both stable and unstable by analyzing long-term field experiments on ex-arable land. In addition we demonstrated that the soil invertebrate fauna (e.g. nematodes, mites and collembola) enhances grassland succession and diversity.
Studying below-ground and above-ground parasites showed that range-expanding (invasive) plant species are less sensitive to pests and pathogens than native species. Our long-term field experiment on ex-arable land, initiated in 1996 in the EU-CLUE project, enables us to study secondary succession from a real temporal perspective. In combination with a chronosequence of more than 35 years, which mimics ongoing secondary succession, we are able to further develop the concept of succession from an above-belowground perspective. In this research theme we also analyze the consequences of diversity in plant-, herbivore- and their natural enemy communities for bottom-up, horizontal and top-down control processes.