Pathogenicity of four Phytophthora species on kauri: in vitro and glasshouse trials
Title information
Author/s
I. Horner, E. Hough
Research provider
Plant & Food Research
Status
Completed
Year
2014
Objectives
Soil surveys to detect PA, targeting sites with kauri trees showing disease symptoms, detected a number of other Phytophthora species (Waipara et al. 2013). P. cinnamomi, P. multivora and P. cryptogea were particularly common. In vitro and glasshouse studies were carried out to determine the relative pathogenicity of these four species, prior to investigating potential interactions among these species in the field.
Outcomes
When excised leaves were inoculated with colonized agar plugs, all four Phytophthora species produced lesions. Lesion advance was significantly slower with P. cinnamomi, P. multivora and P. cryptogea than with PA. Similar results were obtained with inoculated excised twigs. The growth rate of PA through live kauri twig tissue was similar to that on V8 agar.
Potted 2-year-old kauri seedlings were trunk-inoculated. Small lesions (mostly <10 mm over 4 months) appeared with Phytophthora cinnamomi, P. multivora or P. cryptogea, no trees died, and plant growth was suppressed only slightly. When PA-inoculated, lesions spread rapidly, trunks were girdled, and all trees died within 4-6 weeks. All kauri seedlings died within 10 weeks when soil was inoculated with PA. Feeder root damage occurred following soil inoculation with P. cinnamomi, P. multivora or P. cryptogea, and the respective Phytophthora species were readily isolated from root lesions, but there were no plant deaths.
Results suggest that PA is a highly aggressive pathogen on kauri while relatively, the other three species are weaker pathogens.
Potted 2-year-old kauri seedlings were trunk-inoculated. Small lesions (mostly <10 mm over 4 months) appeared with Phytophthora cinnamomi, P. multivora or P. cryptogea, no trees died, and plant growth was suppressed only slightly. When PA-inoculated, lesions spread rapidly, trunks were girdled, and all trees died within 4-6 weeks. All kauri seedlings died within 10 weeks when soil was inoculated with PA. Feeder root damage occurred following soil inoculation with P. cinnamomi, P. multivora or P. cryptogea, and the respective Phytophthora species were readily isolated from root lesions, but there were no plant deaths.
Results suggest that PA is a highly aggressive pathogen on kauri while relatively, the other three species are weaker pathogens.