Phytophthora agathidicida

Abstract

Differential oogonium ornamentation, together with the size of the oospore, was first recognised to be a diagnostic characteristic by Beever et al. (2009) in their study of representative isolates of the members of Clade 5. The mean oospore widths for P. cocois and P. heveae were not significantly different from each other nor from the Clade 5 mean, but oospore width of P. agathidicida is significantly larger than all other species and P. castaneae is significantly smaller than all other species (Weir et al., 2015). Oogonium wall ornamentation of P. agathidicida is mildly stipulate. Oospores nearly fill the oogonia with a mean width of 27.7 µm, and ranging between 19.8-35 µm. Antheridia are amphigynous, globose, and some have knots at the base (Fig. 2). P. agathidicida is homothallic.

Canker and decline diseases caused by soil- and airborne Phytophthora species in forests and woodlands

“…In 1972, Phytophthora isolates were recovered from a dying kauri stand on the Great Barrier Island off the coast of the North Island and morphologically identified as P. heveae ( Gadgil 1974 ). Apparently, not much attention had been paid to managing this local disease outbreak until dieback and mortality of kauri stands were observed 30 years later on the North Island ( Beever et al 2009 , Scott & Williams 2014 , Bellgard et al 2016 ). Symptoms include thinning, chlorosis and dieback of crowns ( Fig.…”

“…5f ), fine root losses and tongue-shaped collar rot lesions with abundant resin exudations extending several meters up the trunk and also into the main roots ( Fig. 5g, h ) ( Beever et al 2009 , Bellgard et al 2016 ). A homothallic Phytophthora species, informally designated as Phytophthora taxon Agathis (PTA) and later described as P. agathidicida , was consistently isolated from necrotic bark lesions and from rhizosphere soil ( Beever et al 2009 , Scott & Williams 2014 , Weir et al 2015 ).…”

Indigenous Biosecurity: Māori Responses to Kauri Dieback and Myrtle Rust in Aotearoa New Zealand

“…Human activities, including the transfer of contaminated soils between nurseries, recreational use of kauri forests, and track building and maintenance practices, have been all correlated to the spread and incidence of the disease (Bellgard et al 2016). Beever et al (2009) andHorner et al (2014) demonstrated how susceptible kauri are to infection and how easily infectious propagules, such as oospores, are transmitted from infected to non-infected plants.…”

“…Only recently has the soil-borne pathogen responsible for 'Kauri Dieback' been taxonomically described and named as P. agathidicida (Weir et al 2015). The pathogen initially infects kauri through its roots before progressing to an aggressive collar rot resulting in large basal trunk lesions, then canopy defoliation and eventually death (Bellgard et al 2016) (Fig. 1).…”

A LAMP at the end of the tunnel: A rapid, field deployable assay for the kauri dieback pathogen, Phytophthora agathidicida

“…Phytophthora agathidicida is identified from the resulting cultures using morphology or molecular diagnostics both of which require trained laboratory staff. The former is typically based upon the size and reflection of the antheridium [14] while an RT-PCR assay targeting the internal transcribed spacer (ITS) regions of the ribosomal DNA [15] is routinely used for identification of cultured P. agathidicida isolates.…”