Homothallism in Pseudoperonospora humuli

D. H. Gent, Y. Cohen, F. Runge

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The downy mildew pathogen, Pseudoperonospora humuli, forms oospores abundantly in diseased hop tissue. Diverse monosporangial isolates of P. humuli derived from samples collected in Japan, Germany and the USA readily formed oospores within hop leaves when inoculated singly, suggesting homothallism. Single zoospore isolates also readily formed oospores within hop leaves, further supporting the homothallic nature of this oomycete. The majority of oospores were deemed viable based on cytoplasm characteristics and plasmolysis assays. However, disease symptoms failed to develop when hop leaves were inoculated with newly formed oospores, even when oospore conditioning was attempted with treatment with potassium permanganate or β-glucuronidase/arylsulphatase, brief exposure to freezing temperature, or passage through an earthworm. Oospores derived from a monosporangial isolate of P. humuli that overwintered outdoors in infested leaves buried in soil also failed to cause downy mildew. Pseudoperonospora humuli is homothallic and oospores of the organism appear to require as yet unknown conditions to stimulate their germination and/or infection.

Original languageEnglish
Pages (from-to)1508-1516
Number of pages9
JournalPlant Pathology
Issue number9
StatePublished - Dec 2017

Bibliographical note

Publisher Copyright:
© 2017 British Society for Plant Pathology


  • Humulus
  • Pseudoperonospora
  • homothallism
  • hop
  • mating system
  • oospore


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