Nine year survival of 16 Phytophthora lateralis resistant and susceptible Port-Orford-Cedar families in a Southern Oregon field trial

Abstract

Port-Orford-cedar (Chamaecyparis lawsoniana) has suffered high mortality from the pathogen Phytophthora lateralis in portions of its natural range in southwest Oregon and northwest California, as well as in horticultural plantings in North America, and more recently in Europe. A program to develop genetically resistant populations of Port-Orford-cedar is underway. This operational program began in 1996 and utilizes artificial inoculation of the roots of young seedlings (or rooted cuttings) to rate parent trees for resistance. A key step to any such program is to establish field trials: to validate the results of artificial inoculation trials; to examine resistance at a range of sites and environments conducive to the pathogen; and to monitor the durability of resistance. The field trial ('Foggy Eden' site) examined here consists of 16 Port-Orford-cedar families established in southern Oregon in 2002 at a site on the Rogue River-Siskiyou National Forest. The Foggy Eden (FE-02) site was chosen because of the notable recent heavy P. lateralis related mortality of the natural Port-Orford-cedar trees in the immediate vicinity. Sixteen families had been selected to cover a range from highly susceptible (100 percent mortality) to highly resistant (0 percent mortality) in a previous short-term greenhouse artificial inoculation ('root dip,' RD) trial. Some of the families were also included in two short-term raised bed (RB) trials, where the raised bed had been previously infested with P. lateralis. By summer 2010, overall mortality at FE was 42.7 percent (263 of 616 trees). Most of the mortality occurred by 2006 (244 trees). Family variation in survival ranges from 20.8 to 93.8 percent. The top three families for survival involve a common parent and all have less than 11 percent mortality. The comparison of the results from FE-02 with the short-term 'root dip' and raised bed tests showed a strong relationship between these trials. The results are encouraging at this point, but the trial needs to be followed longer, and the results from the additional trials in other environments conducive to P. lateralis need to be examined to determine the efficacy of resistance in different environments. Resistant seed from wind-pollinated orchards is now available to aid restoration and reforestation.

Parent Publication

• Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forestry: Disease and insect resistance in forest trees

Citation

Sniezko, Richard A.; Hamlin, Jim; Hansen, Everett M.; Lucas, Sunny. 2012. Nine year survival of 16 Phytophthora lateralis resistant and susceptible Port-Orford-Cedar families in a Southern Oregon field trial. In: Sniezko, Richard A.; Yanchuk, Alvin D.; Kliejunas, John T.; Palmieri, Katharine M.; Alexander, Janice M.; Frankel, Susan J., tech. coords. Proceedings of the fourth international workshop on the genetics of host-parasite interactions in forestry: Disease and insect resistance in forest trees. Gen. Tech. Rep. PSW-GTR-240. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture. pp. 348-355.