Soil moisture and temperature conditions affect survival and sporulation capacity of Rhododendron leaf disks infested with Phytophthora ramorum
| Authors: | Ebba K. Peterson, Niklaus J. Grünwald, Jennifer L. ParkeSoil |
| Year: | 2017 |
| Type: | General Technical Report |
| Station: | Pacific Southwest Research Station |
| Source: | Proceedings of the sudden oak death sixth science symposium. Gen. Tech. Rep. GTR-PSW-255. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 81-82. |
Abstract
Soilborne inoculum (infested leaf debris which has become incorporated into the soil) may be an important contributor to the persistence of the sudden oak death pathogen Phytophthora ramorum in recurrently positive nurseries. To initiate new epidemics, soilborne inoculum must not only be able to survive over time, but also be capable of producing sporangia during times favorable to infection of plant material at the soil surface.
To accompany field studies of the epidemiological risk of soilborne inoculum in nurseries, laboratory assays were performed investigating how incubation of inoculum at various temperature and moisture regimes affects sporulation capacity and survival of P. ramorum. For all experiments, wounded rhododendron leaves were infected with P. ramorum zoospores and then incubated for 2 to 3 weeks. Leaf disks were punched out of the lesioned areas, which were inserted into mesh sachets and placed at the various moisture and temperature treatments. Over time we recovered sachets and placed the disks in tubes containing filtered creek water at 20°C to induce sporulation. The tubes were vortexed after 1 week and the water was filtered to capture sporangia, then the leaf disks were plated on selective media to discern how incubation conditions affected survival.