This is a blog about the native conifers of the Pacific Northwest. It is a companion to the Northwest Conifers site. The blog will focus on timely and interesting details about our conifers, their connections to the rest of the environment, and our connection to them.

Thursday, November 17, 2016

Dorena Genetic Resource Center Visit

In October, Martin Nicholson, Curator at Hoyt Arboretum, took a group of us on a day trip to the Dorena Genetic Resource Center a few miles south of Eugene. The Dorena Center is a US Forest Service facility that does genetic research to find disease resistant conifers, focusing on white pine and Port Orford cedar. Seedlings grown at the Center are planted in seed orchards to produce large numbers of seeds, which can be used for reforestation and restoration. We met Richard Sniezko (Center Geneticist and Acting Manager), who gave us a tour of the facility at Dorena and the BLM's Tyrrell Seed Orchard, located southwest of Eugene in the Coast Range.

White pines growing at the Dorena Genetic Resource Center

White pine blister rust 

White pine blister rust
The primary focus of the Center is white pine blister rust (scientific name Cronartium ribicola). This pathogen is an invasive fungus that attacks five-needle pines, often with deadly results. In the Pacific Northwest, these pines include western white pine (Pinus monticola), sugar pine (Pinus lambertiana), and whitebark pine (Pinus albicaulis). Whitebark pine in particular has been devastated by white pine blister rust. 

To begin research on finding resistant pines, researchers gather seeds from various locations and grow seedlings. To expose the seedlings to the white pine blister rust, researchers gather infected leaves of shrubs like currants and gooseberries. The rust requires two host species to complete its life cycle. One is a species of white pine. The other can be a variety of plants, locally, usually shrubs like currants and gooseberries. The infected shrubs infect the trees, and the trees in turn infect more shrubs. The seedlings at Dorena are infected or "inoculated," as Richard Sniezko put it, by placing them in a large room under a screen that holds the infected leaves of the shrubs. Artificial fog is piped into the room, where water collects on the leaves and drips onto the white pine seedlings, carrying the rust spores with it.

Whitebark pines tested for resistance to blister rust.
Some survive,  others, not so much.
The inoculated seedlings now can be grown to see which ones are rust resistant. Genetically similar seedlings (called a family) are arrayed in a row, with other families in other rows. After a few years, the differences between families is striking, with some surviving and others completely dead.

Once rust-resistant specimens are identified, they can be grown for seed to be used for restoration and reforestation. To meet the demand for seed, resistant trees are grown at the Tyrrell Seed Orchard, and other seed orchards in the Pacific Northwest.

Note that the center develops diverse families of resistant seed.  This is important for two reasons: (1) It enables foresters to restore the new seedlings to habitats to which they are adapted. This enhances their ability to thrive in that environment. (2) It maintains genetic diversity among the planted trees. This enables them to adapt more readily to future changes and survive other diseases.

White pines at the BLM's Tyrrell Seed Orchard
Whitebark pine has been devastated by white pine blister rust in many areas, including the Cascade Mountains. You can see how the Dorena Center has been helping with restoring whitebark pine at Crater Lake in this Oregon Field Guide video. Since the filming, new plantings of rust-resistant whitebark pines have been planted at several locations around the rim of Crater Lake, including one planting near Crater Lake Lodge. Also, see this OPB report on whitebark pine, and another Oregon Field Guide video on the Tyrrell Seed Orchard

It is noteworthy that most of the whitebark pine in the Northwest is located in wilderness. The legal definition of wilderness in the 1964 Wilderness Act expresses the idea that wilderness is to be a place where natural processes are allowed to run their course without human interference. This would seem to preclude planting resistant pines in wilderness. However, in the case of white pine blister rust, it has been human interference that introduced the pathogen into the wilderness. US Forest Service regulations now allow forest restoration in wilderness when we can't reasonably expect that the forest can recover naturally. However, in some cases, it makes sense to leave recovery to natural processes and learn from what happens naturally.

Cedar root disease

The Dorena Genetic Resource Center also works with Oregon State University to research and grow Port Orford cedar (Chamaecyparis lawsoniana) that is resistant to cedar root disease. This pathogen (Phytophthora lateralisis an introduced fungus-like water mold that is related to brown algae. It was first reported in the United States on ornamental Port Orford cedar seedlings near Seattle in 1923. By 1952, it had spread to the natural range of Port Orford cedar near Coos Bay, Oregon. Since then, it has spread throughout the range of Port Orford cedar in southwest Oregon and northern California, killing large numbers of trees. It has also attacked cultivars of Port Orford Cedar, adversely affecting the horticulture industry.  It also can kill Pacific yew (Taxus brevifolia) growing near infected cedars. Western red cedar (Thuja plicata) is resistant to the disease but can be infected. 

Pine and cedar seedlings
Researchers have located Port Orford cedars growing in the wild that are apparently resistant to cedar root disease and have used these for a program to grow seeds of resistant trees. One approach is to grow small trees for seed in a greenhouse at the Center. The trees are treated with gibberellic acid, a hormone that stimulates them to produce cones at an early age. This quickly provides seeds to grow resistant seedlings.

Diverse plantings of Port Orford cedars are also growing at the Tyrrell Seed Orchard to provide resistant seed for planting. As with the pines, it is important to maintain genetic diversity in forest habitats and to plant new seedlings in habitats to which they are adapted.

Port Orford cedar at the Tyrrell Seed Orchard 
One possible monkey wrench in the program of developing disease resistant trees is that the pathogens that attack them can also undergo genetic changes so that they are lethal to the resistant trees. This could mean job security for geneticists fighting the diseases. It's likely to be a continuing battle. 

Sources and more info

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