Point Reyes Participates in Sudden Oak Death Resistance Research

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Date: September 1, 2006
Contact: Jane Rodgers, 415-464-5190

In collaboration with the US Forest Service, UC Berkeley, UC Davis and the Mid-Peninsula Open Space District, Point Reyes National Seashore will be investigating the ability of tankoaks (Lithocarpus densiflorus) to resist Sudden Oak Death (SOD) caused by the pathogen Phytophthora ramorum. Led by UC Berkeley geneticist Richard Dodd, this five year program proposes to provide regional information regarding genetic variation in resistance to SOD in tanoak, including its frequency in natural populations and geographic variation.

Acorn and leaf collections in fall 2006 will initiate the four phases of this project: (1) resistance testing, (2) establish a short-term common garden study, (3) implement a ‘long-term’ field study, and (4) molecular genetics work. Collections will be made from five widely separated geographic sources of tanoak (coastal sites from just south of Monterey to southern Oregon and an interior Sierra Nevada site). The different phases of the project will be headed up by separate investigators, but with exchange of information and materials and collaboration. The different phases of this project should help give insights on the SOD-tanoak interactions as well as provide baseline data on molecular genetic variation and quantitative genetic variation of tanoak.

Tanoak may be the most susceptible species to SOD in the western United States, with documented mortality rates of over 60%. Little information is available to predict how many, if not all, tanoaks will die in the next 10 or 20 years. Much of the range of tanoak occurs in high risk areas for SOD, and this species and its associated ecosystems could be dramatically altered by high levels of mortality in the next several decades. The ultimate fate of tanoak from impacts of SOD in high hazard areas may depend significantly on what levels of genetic resistance exist.

As with many virulent pathogens, the frequency of resistance is expected to be very low. The frequency of resistance is expected to be higher in any stands where SOD has already caused high mortality since a high percentage of susceptible trees have already died. Understanding more about the genetic diversity within tanoak and variation in resistance to P. ramorum, will help us understand potential expansion of the range of this pathogen and its intensification in currently infested areas, and what land managers might do to maintain populations of tanoaks.


Last updated: February 28, 2015

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