dr.ir. J (Hans) Helder

dr.ir. J (Hans) Helder

Associate Professor

Research conducted by the Laboratory of Nematology is part of the research program of the Graduate School Experimental Plant Sciences (EPS) and the C.T. de Wit Graduate School for Production Ecology & Resource (PE&RC).

Research:

"Never change a winning team" could have been the motto of nematodes, a group of worm-like animals that arose in the early Cambrian (more than 500 million years ago) in a marine habitat. Keeping in mind the age of this group of animals, the morphological diversity of nematodes is (very) low. This is the main reason why morphology-based systematics of nematodes had been volatile for decades. Yet another consequence relates to community monitoring. Microscopic analysis is very time and labor intensive, and this has limited a wider use of nematodes as bio-indicators.

Fortunately, the molecular diversity among nematodes is high, and this offers great new opportunities. We have generated a phylum-wide database that contains digital pictures from individual nematodes as well as molecular date - mostly full length small subunit ribosomal DNA (=1,700 bp) or the 5' end of the large subunit rDNA ((=1,000 bp - from that particular individual. The overall SSU rDNA alignment - probably the largest one in the world- includes at the moment (January 2013) over 2,700 taxa.

Currently, we are working on nematode phylogenetics and the evolution of plant parasitism ("what do you need to be a plat parasite?" and "how the necessary genes were acquired?"). Apart from this, we are developing a molecular tool for nematode community analysis at family and/or genes level (see also Maturity Index). We have generated dozens of sets of family, genus or species-specific PCR primers. The DNA barcoding tools make life of a soil ecologist and pathologists easier. A parasitic life style accelerates eveolution and therefore we could develop quantitative (qPCR-based) assays at species level for notorious plant parasites such as root knot, cyst, lesion and burrowing nematodes. For this we cooperate intensively with Prof. dr. Gerrit Karssen (Dutch Plant Protection Service) and a number of academic and non-academic partners. Apart grom these phytopathological aspects, we concentrate on the biodiversity and ecology of nematode communities in soil and sediments to monitor and better understand the biological conditoin of agro-ecological and (semi) natural habitats.

Research group:

  • Sven van den Elsen
  • Paula Harkes
  • Casper Quist
  • Joris van Steenbrugge
  • Jet Vervoort