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​​​​​​The Genus ​Phytophthora​ – Don’t Change a Winning Concept​?

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​Event Format & Dates

​Live & Fully Virtual

Session 1 Agenda​​​​​ - Recording Posted!

Moderated by Niklaus Grunwald​

  • Welcome to Delegates by Niklaus Grunwald 
  • "The Phytophthora genus - history, characteristics and the case for retaining the concept" presented by​ Clive Brasier, Niklaus Grunwald, Tyler Bourret, David Cooke, Francine Govers, Bruno Scanu, Thomas Jung 
  • "Phylogenomics of Phytophthora and suggestions to deal with its taxonomic implications​" presented by​ Marco Thines ***Marco was unable to participate
  • "Peronosporaceae phylogenetics" presented by​ Michael Seidl, Tyler Bourret
  • "Biological cohesion and synapomorphy within Phytophthora - and its contrast to Pythiumpresented by Thomas Jung 
  • "European forest disease syndromes involving multiple Phytophthora species and clades" presented by Bruno Scanu 
  • "Protection of the genus Phytophthora for international scientific and research communication" presented by Joan Webber 

Session 2 Agenda - Recording Posted!

Moderated by David Guest​

  • Welcome to Delegates by Niklaus Grunwald 
  • "The impact of Phytophthora in the tropics" presented by​ André Drenth 
  • "Phytophthora diversity and ecosystem management in Australasia​" presented by Giles Hardy & Mia Townsend 
  • "Phytophthora risk and regulation in California" presented by Heather Martin
  • "Importance of ‘genus stability’ in the management and regulation of Phytophthoras on native plants in Western North America" presented by Susan Frankel
  • "What Does Comparative Mitochondrial Genomics tell us?" presented by Frank Martin 
  • "How do we infer patterns and processes structuring Phytophthora populations" presented by Niklaus Grunwald 

​Session 4 Agenda

Moderated by Tanay Bose​

Part 1 - Recording Posted!

  • Welcome to Delegates by Niklaus Grunwald 
  • "Breeding system flexibility and the global success of Phytophthorapresented by​ Clive Brasier 
  • "Identification and characterization of Phytophthora hybrids using GBS and flow cytometry​" ​presented by Kris Van Poucke 
  • "Common ground and shifting paradigms: How to reconcile Phytophthora evolution, cladistics, taxonomy, and biosecurity" presented by Tyler Bourret
  • "Don’t fix what ain’t broke: the name Fusarium " presented by David Geiser 
  • "Relevant ICNafp rules and other options available to retain established genus names and circumscriptions" presented by David Hawksworth 

Part 2 - Recording Posted!​

  • Break out Session including presentation of three 'statements' for consideration led by Francine Govers
  • Workshop Summary led by David Cooke
  • Wrap-up including next steps​ led by Francine Govers

Online Discussion - Supplemental online discussion throughout the event via Slack

    Global Event Times

    RegionReference CityMonday, April 22
    Tuesday, April 23​Thursday, April 25
    Day 1 Start Time Day 2 Start Time Day 4 Start Time
    North AmericaMinneapolis09:0017:0009:00
    South AmericaR​io de Janeiro11:00
    AfricaCape Town16:0024:0016:00
    Asia (Western)New Delhi19:3003:30 (4/24/2024)
    Asia (Eastern)Hong Kong22:0006:00 (4/24/2024)

    Event Overview

    The genus Phytophthora is an ancient, historic, biologically and structurally cohesive and evolutionarily successful generic concept. Comprising more than 200 species across at least 13 clades, it shows paraphyly with two downy mildew clades.

    This virtual event is convened to assess the scientific support for retaining the name Phytophthora for all major clades of the genus. The workshop will explore the evolutionary, biological, taxonomic, regulatory, social and economic ramifications involved. 

    Talk topics will encompass:

    • ​​Overview of the Phytophthora paraphyly and cladism issue (including history of the genus)
    • Proposal to split Phytophthora into multiple genera
    • Update on the phylogeny of the oomycetes since 2000
    • Adaptation and evolution of the Downy Mildews
    • Structure and evolution of oomycete genomes (including trans generic effector distribution)
    • Lessons from molecular clocks and coalescence analyses
    • Biological cohesion across the Phytophthora clades (including lack of major discriminating synapomorphies)
    • Phytophthora breeding systems
    • Role of ancient reticulation and recent hybridization events in Phytophthora and other oomycetes
    • Economic impact of Phytophthora pathogens (including multiple clade involvement in major disease syndromes)
    • Importance of conserving the Phytophthora genus in its current form for regulation, disease management and scientific communication​
    • Evolutionary process versus taxonomic cladism
    • The Fusarium nomenclatural conflict
    • Relevant ICNafp protocol and its possible role in genus preservation

    Virtual Event Outcomes

    All scientists working on the genus Phytophthora and other oomycetes are encouraged to actively participate in weighing the evidence and to vote on a recommendation aimed at reaching a community consensus.

    Organizing Committee

    • Tyler Bourret ​ United States Department of Agriculture (USDA), Agricultural Research Service, Mycology and Nematology Genetic Diversity and Biology Laboratory, Beltsville, Maryland, USA
    • Clive Brasier  Emeritus Mycologist, Tree Health, Forest Research, Farnham, UK
    • David E.L. Cooke ​ The James-Hutton-Institute, Cell and Molecular Sciences, Dundee, UK
    • Francine Govers ​ Wageningen University and Research, Laboratory of Phytopathology, Wageningen, the Netherlands
    • Nik Grünwald ​ United States Department of Agriculture (USDA), Agricultural Research Service, Horticultural Research Unit, Corvallis, Oregon, USA
    • Thomas Jung ​ Mendel University in Brno, Department of Forest Protection and Wildlife Management, Brno, Czech Republic
    • Bruno Scanu ​ University of Sassari, Department of Agriculture Sciences, Sassari, Italy


    • APS Members and Non-Members: $49
    • APS Student and Early Career Members: $20
    • Development Economy Registration is complimentary for individuals residing or working in qualifying countries.

    Limited space is available! Registration is now closed​.


    Registrations are final and cannot be refunded. 

    Expected Behavior

    We are dedicated to providing a harassment-free experience for everyone, regardless of gender, sexual orientation, disability, physical appearance, body size, race, or religion. We do not tolerate harassment of participants in any form. We ask all attendees, exhibitors, speakers, sponsors, volunteers, guests and other participants be considerate and respectful to all members and refrain from demeaning, discriminatory, or harassing behavior and speech. Please note, if you register a guest for the meeting, you may be held responsible for the actions of the guest. Violations of this policy should be reported to meeting staff. 

    APS reserves the right to remove any individual from attendance or other participation in any APS sponsored event without prior warning or refund, and to take additional action as determined necessary, up to and including expulsion from participation in APS. Any course of action recommended by APS is final.

    The American Phytopathological Society
    3285 Northwood Circle, Suite 100
    St. Paul, MN 55121
    Telephone: +1.651.454.7250
    Fax: +1.651.454.0766