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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Disease and Pest Management Research Unit » Research » Publications at this Location » Publication #373221
Research Project: Integrated Disease Management of Exotic and Emerging Plant Diseases of Horticultural Crops

Location: Horticultural Crops Disease and Pest Management Research Unit

Title: Growth, infection and aggressiveness of phytophthora pathogens on rhododendron leaves

Author
item TAYLOR, CLARE - Oregon State University
item Grunwald, Niklaus - Nik

Submitted to: CABI Agriculture and Bioscience (CABI A&B)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2021
Publication Date: 6/30/2021
Citation: Taylor, C., Grunwald, N.J. 2021. Growth, infection and aggressiveness of phytophthora pathogens on rhododendron leaves. CABI Agriculture and Bioscience (CABI A&B). 2:26. https://doi.org/10.1186/s43170-021-00048-5.
DOI: https://doi.org/10.1186/s43170-021-00048-5

Interpretive Summary: Phytophthora pathogens are well known as important or emerging pathogens. The plant genus Rhododendron can be infected by many Phytophthora pathogens. Few studies have directly contrasted the foliar epidemiology of different Phytophthora species on a given host. We investigated differences in the foliar epidemiology of twelve Phytophthora pathogens infecting Rhododendron. Our research was conducted using single detached leaves, whole plant growth chamber assays, and whole plant field studies. P. syringae stood out as a relatively weak pathogen, showing poor spore production and low levels of disease severity, except at low temperatures. P. parasitica was consistently able to grow at higher temperatures than any of the other Phytophthora spp. and showed higher aggressiveness than any of the other species at high temperatures. P. cinnamomi and P. cactorum, typically thought of as root-infecting species, were able to cause as much foliar disease as P. syringae a foliar pathogen. P. kernoviae was consistently among the most aggressive species with the highest sporulation. These results provide novel insights into the comparative epidemiology of these important established and emerging Phytophthora species.

Technical Abstract: Background Phytophthora species are well known as important or emerging pathogens. The genus Rhododendron is of considerable importance to plant regulatory agencies because it is host to many Phytophthora species, most notably, P. ramorum and P. kernoviae. Few studies have directly contrasted the epidemiology of different Phytophthora spp. on a given host. Methods We investigated aspects of the foliar epidemiology (lesion size, sporulation and temperature responses) of P. cactorum , P. cambivora , P. cinnamomi , P. citrophthora , P. foliorum , P. kernoviae , P. lateralis , P. nemorosa , P. nicotianae , P. plurivora , P. ramorum and P. syringae on Rhododendron in detached leaf, whole plant chamber, and field studies. Results P. syringae stood out as it appeared to be a relatively weak pathogen, showing no sporulation and low levels of disease severity, except at low temperatures. P. nicotianae was consistently able to grow at higher temperatures than any of the other Phytophthora spp. and showed higher aggressiveness than any of the other species at high temperatures. P. cinnamomi and P. cactorum , typically thought of as root- infecting species, were able to cause as much foliar disease as P. syringae , a foliar pathogen. P. kernoviae was consistently among the most aggressive species with the highest sporulation. Conclusion These results provide novel insights into the comparative epidemiology of these important established and emerging Phytophthora species.