1. Serological: An Enzyme-Linked ImmunoSorbent Assay (ELISA) Reagent Set for Phytophthora
(AGDIA, Cat# SRA 92600/1000) at the genus level for primary screening. A positive does not indicate P. kernoviae
Identification must be confirmed by other methods.
2. Molecular: Real-time polymerase chain reaction (qPCR) is approved for species identification (see Notes). To request a copy of these protocols, email the S&T Beltsville laboratory at APHIS-PPQCPHSTBeltsvilleSampleDiagnostics@aphis.usda.gov and use the subject line "Diagnostic protocol request". Diagnostic Resources: IDphy
: molecular and morphological identification of Phytophthora
, a tool that supports morphological and molecular identification of Phytophthora
spp. including P. austrocedrae
, developed by PPQ in collaboration with Phytophthora
Symptoms in infected hosts are very similar to those of P. ramorum, which infects some of the same hosts. However, P. kernoviae has clear morphological distinctions from P. ramorum (Aleksandrov and Arbuzova, 2012). Compared to P. ramorum, which often occurs in similar habitats in the UK, P. kernoviae is homothallic instead of heterothallic, is papillate instead of semi-papillate, does not produce chlamydospores, and has a longer pedicel length (Dick and Parke, 2012).
P. kernoviae may be distinguished from other homothallic Phytophthora species with caducous, papillate sporangia with medium-length pedicels by its lower optimal temperature (cfr. P. botryosa, and P. hevea); higher optimum temperature (cfr. P. nemerosa), often tapered oogonial stalks (cfr. P. meadii, P. botryosa, P. nemerosa), often asymmetric sporangia (cfr. P. meadii, P. megakarya, P. nemerosa), and longer pedicels (cfr. P. boehmeriae) (Brasier et al., 2005; Dick and Parke, 2012).
Widmer (2010) developed a diagnostic key to differentiate P. kernoviae from other Phytophthora species that infect the foliage of Rhododendron.
3/13/2020: The qPCR protocol uses the Cepheid SmartCycler thermocycler machine. In 2019, the manufacturer discontinued this machine. The S&T Beltsville laboratory is currently adapting the protocol for a different machine. Diagnostic labs may use the protocol for the Cepheid SmartCycler if their machine is in good condition. For the 2020 survey season, please contact the diagnostic laboratory you use for screening to confirm their capacity before you begin collecting samples.