Preserving the Biologically Coherent Generic Concept of Phytophthora, “Plant Destroyer”

Abstract

<i>Phytophthora</i> is a long-established, well-known, and globally important genus of plant pathogens. Phylogenetic evidence has shown that the biologically distinct, obligate biotrophic downy mildews evolved from <i>Phytophthora</i> at least twice. Because, cladistically, this renders <i>Phytophthora</i> "paraphyletic," it has been proposed that <i>Phytophthora</i> evolutionary clades be split into multiple genera (Crous et al. 2021; Runge et al. 2011; Thines 2023, 2024). In this letter, we review arguments for the retention of the generic name <i>Phytophthora</i> with a broad circumscription made by Brasier et al. (2022) and by many delegates at an open workshop organized by The American Phytopathological Society. We present our well-considered responses to the genus splitting proposals, both in general terms and in terms of the specific proposals for new genera, alongside new information regarding the biological properties and mode of origin of the <i>Phytophthora</i> clades. We consider that the proposals are mostly non-rigorous and not supported by the scientific evidence. Further, given (i) the apparent lack of any distinguishing biological characteristics (synapomorphies) between the <i>Phytophthora</i> clades; (ii) the fundamental monophyly of <i>Phytophthora</i> in the original Haeckelian sense (Haeckel 1877); (iii) the fact that paraphyly is not a justification for taxonomic splitting; and (iv) the considerable likely damage to effective scientific communication and disease management from an unnecessary breakup of the genus, we report that workshop delegates voted unanimously in favor of preserving the current generic concept and for seeking endorsement of this view by a working group of the International Commission on the Taxonomy of Fungi. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

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