The susceptibility of rare and threatened NSW species to the root-rot pathogen Phytophthora cinnamomi: 1. Initial testing and identification of key research questions

In Australia disease caused by Phytophthora cinnamomi can have devastating impacts on native vegetation, especially on plant species with restricted distributions. The identification of susceptible threatened species is a crucial first step in understanding disease aetiology and selecting appropriate management. In a glasshouse trial, plants of 16 rare and threatened New South Wales native species from 10 families were inoculated with the pathogen. Phebalium squamulosum spp. alpinum was included as a susceptible control. We found that three species are highly susceptible to the pathogen (Nematolepis rhytidophylla (Albr. & N.G.Walsh) Paul G.Wilson, Prostanthera marifolia R.Br., Pultenaea sp. ‘Genowlan Point’); four others (Hibbertia spanantha Toelken & A.F.Rob, Phebalium bifidum P.H.Weston & M.J.Turton, Plinthanthesis rodwayi (C.E.Hubb.) S.T.Blake, Pomaderris delicata N.G.Walsh & Coates) are likely to be susceptible based on symptoms. The remaining species had few or no plant deaths and no pathogen recovery from the roots. All of the species regarded as highly susceptible are known from single populations. Following these results, subsequent research will assess the efficacy of prophylactic treatment on highly susceptible threatened species, and test whether glasshouse tests are indicative of field responses. Other threatened species will also be tested for susceptibility.