Netherlands Journal of Plant Pathology

, Volume 91, Issue 2, pp 65–76 | Cite as

Fitness of isolates of Sphaerotheca fuliginea resistant or sensitive to fungicides which inhibit ergosterol biosynthesis

  • H. T. A. M. Schepers
Article

Abstract

Isolates ofSphaerotheca fuliginea resistant to fungicides which inhibit ergosterol biosynthesis (EBIs: bitertanol, fenarimol, imazalil) had been collected from glasshouses in the Netherlands. Fitness of these isolates was compared to that of isolates with a wild-type sensitivity to EBIs. Fitness parameters studied were germination of conidia, growth of germ tubes and mycelium, penetration, sporulation and competitive ability.

In an experiment in which 10 EBI-resistant isolates were compared to 7 wild-type isolates, one or more values of fitness parameters for EBI-resistant isolates were slightly lower than those for the wild-type isolates. However, within the group of resistant isolates no relation existed between the degree of resistance to EBIs and the degree of fitness. In an experiment with fewer isolates but with more replicates, differences in fitness between EBI-resistant and wild-type isolates were not detected over a three-month period.

In competition experiments in which no crowding was present, resistant isolates competed well with the wild-type isolate.

It is concluded that the hypothesis that resistance to EBIs is unlikely to develop under practical conditions because of decreased fitness of EBI-resistant strains, does not seem to hold forS. fuliginea.

Samenvatting

Uit kassen in Nederland waren isolaten vanSphaerotheca fuliginea verzameld, die resistent waren tegen fungiciden die de ergosterol-biosynthese remmen (EBR's: bitertanol, fenarimol, imazalil). De ‘fitness’ van deze isolaten werd vergeleken met die van isolaten met een wild-type gevoeligheid voor EBR's. De volgende ‘fitness’-parameters werden bestudeerd: sporekieming, groei van kiembuizen en mycelium, penetratie, sporulatie en competitievermogen.

In een proef, waarin 10 EBR-resistente isolaten werden vergeleken met 7 wild-type isolaten, waren één of meer ‘fitness’-parameters iets lager dan die van de wild-type isolaten. Binnen de groep van de resistente isolaten bestond geen relatie tussen de mate van resistentie tegen EBR's en de waarden van de ‘fitness’-parameters. In een proef met iets minder isolaten maar met meer herhalingen in de tijd, werden geen verschillen in ‘fitness’ waargenomen tussen de EBR-resistente en wild-type isolaten. In competitieproeven waarin een epidemie zich kon ontwikkelen, concurreerden de resistente isolaten goed met het wild-type isolaat.

Er wordt geconcludeerd dat de hypothese dat resistentie tegen EBR's in de praktijk waarschijnlijk niet zou optreden vanwege een verminderde ‘fitness” van de EBR-resistente isolaten, niet van toepassing is opS. fuliginea.

Additional keywords

cucumber powdery mildew bitertanol fenarimol imazalil 

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Copyright information

© Koninklijke Nederlandse Planteziektenkundige Vereniging 1985

Authors and Affiliations

  • H. T. A. M. Schepers
    • 1
  1. 1.Laboratory of PhytopathologyAgricultural UniversityWageningenthe Netherlands

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