Susceptibility to the rare Phytophthora tentaculata and to the widespread Phytophthora cactorum is consistent with host ecology and history

Abstract

We evaluated the susceptibility of three California endemic plant species Heteromeles arbutifolia, Platanus racemosa and Quercus agrifolia to the two congeneric soilborne pathogen species: Phytophthora tentaculata and Phytophthora cactorum. These pathogens were recently introduced in ecosystems east of the San Francisco Bay, where the three plant species above are dominant. Phytophthora cactorum has a worldwide distribution inclusive of California, and a broad host range. Phytophthora tentaculata, in contrast, is suspected to be a “new” exotic to California and has been described on relatively few hosts. By separately challenging the roots and the stems of the three plant species above, we show that: (a) Both were equally pathogenic, but the type of disease differed based on host; (b) disease was consistent with host ecology and with previous disease reports, even if caused by different Phytophthora spp. and; (c) there were intraspecific differences in virulence. This study provides the following significant information regarding the management and early modelling of polyphagous soilborne Phytophthoras: (a) Endemic species can be as problematic as recently introduced exotics. (b) Multiple introductions should be avoided due to varying virulence levels among genotypes. (c) Riparian species like P. racemosa may develop disease tolerance in their root systems, but remain susceptible in their aerial portions, and thus, diseases could be facilitated by flooding or splash of infectious structures of soilborne pathogens onto aerial plant portions.

Control of Phytophthora species in plant stock for habitat restoration through best management practices

“…This Phytophthora species occurs worldwide, and it is known to parasitize over 200 different plant species across many different plant families, particularly in regions with temperate climates (Erwin & Ribeiro, ). Yet, many of the plant hosts of P. cactorum reported here are new, and novel genotypes of this pathogen appear to display increased pathogenicity, at least on some hosts (Sims & Garbelotto, ), suggesting this pathogen is emerging as a greater threat than previously predicted. Phytophthora cactorum has been reported as absent or rare in North America outside of restoration sites (Balci et al ., ; Reeser et al ., ; Sims et al ., ), while its incidence has been reported as high in both restoration sites (Bourret, ) and restoration nurseries (this study).…”

Morphology, Molecular Phylogeny, and Fungicide Sensitivity of Phytophthora nagaii and P. tentaculata in Korea

“…This plant pathogen Phytophthora tentaculata , known for causing root and stalk rot, was initially isolated in a German nursery in 1993, where it affected plants such as Chrysanthemum , Verbena , and Delphinium species [ 54 ]. Due to its ability to cause substantial economic harm to both the nursery industry and native plant species [ 62 ], it is considered one of the top five most concerning Phytophthora species in the United States [ 63 , 64 ]. Later, this pathogen was also discovered in Spain, affecting Verbena plants [ 65 ].…”

The Never-Ending Presence of Phytophthora Species in Italian Nurseries

“…Another notable Phytophthora species is P. lateralis Tucker and Milbrath, which was isolated from nurseries in Washington State before spreading through forests of Chamaecyparis lawsoniana A. Murray bis Parl in Oregon [ 23 ]. Similarly, P. tentaculata Kröber and Marwitz, spread from native plant nurseries onto restoration sites [ 24 , 25 , 26 ].…”