Assessment of Australian native annual/herbaceous perennial plant species as asymptomatic or symptomatic hosts of Phytophthora cinnamomi under controlled conditions

Abstract

Summary Phytophthora cinnamomi is a necrotrophic pathogen of woody perennials and devastates many biomes worldwide. A controlled perlite–hydroponic system with no other hyphae‐producing organisms as contaminants present allowed rapid assessment of ten annual and herbaceous perennial plant species most of which have a wide distribution within the jarrah (Eucalyptus marginata) forest in Western Australia where this pathogen has been introduced. As some annuals and herbaceous perennials have recently been reported as symptomatic and asymptomatic hosts, laboratory screening of some of the field‐tested annuals and herbaceous perennials and additional species was used to further evaluate their role in the pathogen's disease cycle. Nine of the species challenged with the pathogen were asymptomatic, with none developing root lesions; however, Trachymene pilosa died. The pathogen produced thick‐walled chlamydospores and stromata in the asymptomatic roots. Furthermore, haustoria were observed in the roots, indicating that the pathogen was growing as a biotroph in these hosts.

The Use of qPCR Reveals a High Frequency of Phytophthora quercina in Two Spanish Holm Oak Areas

“…Phytophthora cinnamomi, which was found in six dehesas, either from declining or from non-declining trees, is a primary root pathogen of woody species, considered a hemibiotrophic organism with life strategies which can change from biotrophic to necrotrophic, according to the environmental conditions [53][54][55]. This species is also present in plant reservoirs and, depending on its behavior, will determine if the plant remains asymptomatic or not [54][55][56][57]. Furthermore, P. cinnamomi is highly aggressive to holm oaks, as demonstrated previously [11,12,25,[58][59][60].…”

Histopathology of infection and colonization of Quercus ilex fine roots by Phytophthora cinnamomi

“…However, P. cinnamomi can change its behaviour when infecting different hosts. It has been observed that it can survive as a biotrophic organism in symptomless hosts, affecting the frequency of detection of the different resistance/reproduction structures between different host species (Crone et al ., ). Therefore, an accurate description of the pathogen behaviour is important for the study of the pathogenicity of P. cinnamomi on Q. ilex .…”

Phytophthora agathidicida: research progress, cultural perspectives and knowledge gaps in the control and management of kauri dieback in New Zealand

“…; Bellgard et al , ). Such structures are important for persistence and survival of other Phytophthora species such as P. cinnamomi (Crone et al , ; Jung et al , ). Roots and vascular tissue that are colonized with P. agathidicida hyphae and oospores are important propagules that readily dislodge from the hosts and disperse through natural movement in free‐flowing water and soil, and can be vectored by humans, animals and vehicles.…”

“…An important knowledge gap for understanding the basic biology of P. agathidicida and the ecology of kauri dieback is the extent to which P. agathidicida can infect and colonize different plant species in kauri forest, either symptomlessly or as an aggressive primary pathogen. In other forest systems, alternate hosts have been shown to have key ecological roles in the epidemiology of Phytophthora pathogens by acting as sporulating hosts, pathogen refugia, terminal hosts or inoculum bridges (Crone et al , ).…”