Pathogenicity of 21 newly described Phytophthora species against seven Western Australian native plant species

Abstract

The pathogenicity of some Phytophthora species recently described from Western Australia, together with P. cinnamomi as a control, was tested against seven Western Australian native plant species in the glasshouse. Host species were Banksia grandis, B. littoralis, B. occidentalis, Casuarina obesa, Corymbia calophylla, Eucalyptus marginata and Lambertia inermis. Twenty‐two Phytophthora species were grown on a vermiculite, millet seed and V8 substrate and used as soil inoculum when the plant hosts were approximately 3 months old. Pathogenicity was assessed after 6 weeks and plants were scored for death, root damage, and percentage reduction of shoot growth compared with control plants. The pathogenicity of P. cinnamomi was confirmed. Phytophthora niederhauserii was shown to be similar to P. cinnamomi in pathogenicity and of concern ecologically. Other species that killed one or more hosts were P. boodjera, P. constricta, P. elongata, P. moyootj and P. rosacearum, while P. condilina, P. gibbosa, P. gregata, P. litoralis and P. ‘personii’ caused significant reduction to shoot and/or root growth, but did not kill plants. Host species susceptible to the highest number of Phytophthora species were B. grandis, B. littoralis, B. occidentalis and E. marginata. No Phytophthora species tested killed C. calophylla.

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

“…Alone in the south-western Botanical Province of WA, 40 % of the 5 710 endemic plant species from 39 families are susceptible to P. cinnamomi ( Shearer et al 2004 ). Recently, pathogenicity of P. cinnamomi and 21 other Phytophthora taxa from WA, most of them recently described or informally designated new species, to seven native plant species from WA, including Eucalyptus marginata (jarrah), Banksia grandis , B. littoralis , B. occidentalis , Casuarina obesa , Corymbia calophylla (marri) and Lambertia inermis , was demonstrated ( Belhaj et al 2018 ). Eucalyptus marginata and the three Banksia species were susceptible to the highest number of Phytophthora taxa whereas C. calophylla showed the highest resistance to all 21 Phytophthora taxa ( Belhaj et al 2018 ).…”

“…Recently, pathogenicity of P. cinnamomi and 21 other Phytophthora taxa from WA, most of them recently described or informally designated new species, to seven native plant species from WA, including Eucalyptus marginata (jarrah), Banksia grandis , B. littoralis , B. occidentalis , Casuarina obesa , Corymbia calophylla (marri) and Lambertia inermis , was demonstrated ( Belhaj et al 2018 ). Eucalyptus marginata and the three Banksia species were susceptible to the highest number of Phytophthora taxa whereas C. calophylla showed the highest resistance to all 21 Phytophthora taxa ( Belhaj et al 2018 ). Australia has a long history of diebacks of various eucalypt forests, Banksia woodlands and heathlands, which are particularly severe in the Mediterranean climates of WA ( Shearer & Tippett 1989 , Shearer & Dillon 1995 , 1996 , Shearer et al 2004 ) and Victoria ( Weste & Marks 1987 , Marks & Smith 1991 , Laidlaw & Wilson 2003 , Weste 2003 , Cahill et al 2008 ).…”

Susceptibility of Eucalyptus grandis and Acacia mearnsii seedlings to five Phytophthora species common in South African plantations

“…In various trials conducted globally, a substantial variation in the pathogenicity towards an assortment of hosts has been reported among the isolates of P. multivora (Belhaj, Mccomb, Burgess, & Hardy, 2018;Croeser et al, 2018;Rodriguez-Padron, Siverio, Perez-Sierra, & Rodriguez, 2018). In various trials conducted globally, a substantial variation in the pathogenicity towards an assortment of hosts has been reported among the isolates of P. multivora (Belhaj, Mccomb, Burgess, & Hardy, 2018;Croeser et al, 2018;Rodriguez-Padron, Siverio, Perez-Sierra, & Rodriguez, 2018).…”

“…This drawback can be best exemplified using P. multivora. In various trials conducted globally, a substantial variation in the pathogenicity towards an assortment of hosts has been reported among the isolates of P. multivora (Belhaj, Mccomb, Burgess, & Hardy, 2018;Croeser et al, 2018;Rodriguez-Padron, Siverio, Perez-Sierra, & Rodriguez, 2018).…”

Antimicrobials in Phytophthora isolation media and the growth of Phytophthora species

“…The isolation medium NARPH was developed two decades ago and is currently used, without PCNB, as a medium for isolation of Phytophthora species (Belhaj et al ., 2018; Simamora et al ., 2018; Khaliq et al ., 2019). Although growth of three of the 47 species tested in the current study, P. cactorum , P. parvispora , and P. sojae , was severely affected by the antimicrobials in NARH, overall sensitivity to the NARH antimicrobials does not appear to be the reason why many species detected using high‐throughput sequencing are not possible to isolate by baiting.…”