Specificity, pathogenicity and population dynamics of the endoparasitic nematode Heterodera arenaria in coastal foredune

C.D. van der Stoel

Research output: Thesisinternal PhD, WU

Abstract

<em><FONT FACE="Garamond" SIZE=4><p>Key words</em> : <em>Heterodera</em> , plant-parasitic nematodes, soil pathogens, <em>Ammophila arenaria</em> , occurrence, abundance, specificity, population dynamics, life history, pathogenicity, PCR-SSCP, molecular method, escape, sand burial, dispersal, migration, fitness, development time, survival, reproductive success, bottom-up, top-down.</p><p> </p></FONT FACE="Garamond" SIZE=4><p>In natural ecosystems hardly any attention has been given to the population dynamics of plant-parasitic nematodes. In coastal foredunes, plant-parasitic nematodes are supposed to be involved in the degeneration and succession of the dominant sand-fixing grass <em>Ammophila arenaria</em> (Marram grass). The specificity, pathogenicity and population dynamics of the sedentary endoparasitic nematode <em>Heterodera arenaria</em> have been studied to determine if this species might be a key component of the soil pathogen complex of <em>A. arenaria.</p><p>H. arenaria</em> was found to be specific to <em>Elymus farctus</em> and <em>A. arenaria</em> in the mobile area of the coastal foredunes. Colonisation of the newly deposited sand layer by <em>H. arenaria</em> corresponded well with the development of pathogenicity in a series of bioassays. However, direct addition of the nematode to <em>A. arenaria</em> did not result in growth reduction of the plant. So, <em>H. arenaria</em> behaves like a biotrophic parasite, which has a high specificity but is not aggressive. Therefore, <em>H. arenaria</em> did not seem to be directly involved in the degeneration of <em>A. arenaria</em> .</p><p>Each year, the majority of the population of new <em>H. arenaria</em> cysts develops in the newly deposited sand layers. These layers are colonised by <em>A. arenaria</em> roots throughout the growing season. Migration to the new root layer may offer an individual nematode the benefit of early development and a larger potential offspring. The continuous release of juveniles in the field and their development in experiments indicate that release of juveniles from cysts is an ultimately determined process. Juveniles were found to emerge in November and many eggs or juveniles did not survive the winter period. The strategy of release, however, seems effective; the distance of migration could be too large to detect specific cues from the plant and the start of root formation in the field is highly variable. The emergence of juveniles late in the growing season could result in a second generation within the same year. The constant number of cysts per gram of roots suggests that the population density of <em>H. arenaria</em> is most likely a bottom-up directed process.</p>
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • Brussaard, Lijbert, Promotor
  • Woldendorp, J.W., Promotor, External person
  • van der Putten, Wim, Promotor
Award date25 Sep 2001
Place of PublicationS.l.
Publisher
Print ISBNs9789058084361
Publication statusPublished - 2001

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Keywords

  • plant parasitic nematodes
  • heterodera
  • ammophila arenaria
  • plant pathogens
  • population dynamics
  • plant succession
  • pathogenicity
  • sand dune stabilization
  • identification
  • biochemical techniques

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