Tanoak resistance: can it be used to sustain populations?
| Authors: | Katherine J. Hayden, Alex Lundquist, Douglas J. Schmidt, Richard A. Sniezko, Susan J. Frankel, Matteo Garbelotto |
| Year: | 2010 |
| Type: | General Technical Report |
| Station: | Pacific Southwest Research Station |
| Source: | In: Frankel, Susan J.; Kliejunas, John T.; Palmieri, Katharine M. 2010. Proceedings of the Sudden Oak Death Fourth Science Symposium. Gen. Tech. Rep. PSW-GTR-229. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station. pp. 183-188 |
Abstract
Tanoak (Lithocarpus densiflorus) trees are among Phytophthora ramorum’s most susceptible hosts. Extensive mortality in this species has led researchers to question whether selective breeding for resistance can be used to sustain populations; the answer depends on the extent and heritability of pathogen resistance within the host. Consequently, we have undertaken a multi-year common garden study of resistance to P. ramorum in tanoak seedlings grown from acorns collected by collaborators at sites in California and southern Oregon.We have sown 12,650 acorns from nine unique sites in a common garden since 2006. The resulting seedlings have been assayed for resistance to P. ramorum by both detached leaf inoculations using plugs of mycelia as the infective agent, and seedling tip inoculations using a zoospore suspension. Both assays revealed variable resistance with significant heritability. In addition to the laboratory assays, a subset of 800 seedlings from 50 different family groups were planted in a heavily infested, forested site in Monterey County, California. These seedlings are currently being monitored to determine whether there is a correlation between family-level variation in resistance in the laboratory setting to survivorship in the field. After 1 year, the survival rate was 82.5 percent, with no discernable effect of family; however, there were positive identifications of natural infection by P. ramorum.
Together, the data from these studies provide not only background knowledge crucial to predicting the evolutionary and ecological outcomes of the P. ramorum epidemic in tanoak populations, but also for ascertaining any potential for genetic resistance in tanoak to be used as a management tool.