Susceptibility of nine alpine species to the root rot pathogens Phytophthora cinnamomi and P. cambivora.
Phytophthora species are associated with disease in horticulture, agriculture and natural vegetation worldwide but are not well known in cold areas. In Australia, alpine regions have been regarded as unsuitable for the survival and disease expression of Phytophthora cinnamomi, which has caused catastrophic damage to vegetation in other parts of the country. Phytophthora cambivora, on the other hand, has been detected recently in the roots of an endemic alpine shrub (Nematolepis ovatifolia) and may already be exerting pressure on alpine vegetation. We conducted glasshouse susceptibility trials on nine Australian alpine and subalpine shrub species to P. cambivora and P. cinnamomi. The pathogens were re-isolated from the roots of most test species but for some species, few replicates were infected and few died. One species (Phebalium squamulosum) was regarded as highly susceptible with most plants in inoculated pots dying and both pathogens being commonly isolated from roots. The climatic conditions of most populations of the test species are currently unsuitable for disease expression from P. cinnamomi. However, the projected change in temperature in the Australian Alps with climate change will expose most populations of eight of the species to P. cinnamomi activity by 2070. Pathogens are likely to be important drivers of future vegetation in many mountainous areas which are currently not within their range of survival and pathogenesis. Management of these areas should include hygiene and pathogen monitoring, and minimise disturbances that heighten stress for susceptible species.