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

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Event Format & Dates

​Live & Fully Virtual

April 22, 2024 – Presentations with Q&A​

  • ​Morning Session – Americas/ Europe/Africa | Time: 9:00 am – 1:00 pm US Central Time

April 23, 2024 – Presentations with Q&A​​

  • Evening Session – Asia Pacific | ​Time: 5:00 pm – 9:00 pm US Central Time​

April 24, 2024 – Review Session Recordings​

  • ​Attendees in Europe/Africa and Asia Pacific are expected to attend only one of the previous sessions, although programming is different each day. This day is reserved for attendees to view recordings of missed sessions. Recordings will be made available to all attendees after the close of each session.

April 25, 2024 – Presentations, Discussion, Synopsis, and Closing Session

  • Morning Session | ​Time: 9:00 am – 12:30 pm US Central Time

Online Discussion - Supplemental online discussion throughout the event via Slack

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.

Register Now!

Limited space is available! Registration closes Sunday, April 21​, 2024.


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