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4 Facts About Using Genetics in Pursuit of a More Perfect Christmas Tree

December 20, 2018
What will your Christmas gifts be placed under this year? A Fraser fir? A Douglas fir? An artificial tree?

While some individuals love the look and smell of a real Christmas tree, others prefer the low upkeep and longevity of an artificial tree.

But what if we could use genetics to improve the Christmas tree? Would you trade in the fake tree for a fir that loses less needles and requires less upkeep?

Here are four facts about using genetics in pursuit of a more perfect Christmas tree:

1) Very little has been known about the genomes of Christmas trees. Megan Molteni of Wired reported last year:
“…the conifer genome is not just enormous—20 billion base pairs compared to your 3 billion—but also pretty weird. At some point in their deep past, spruces, pines, firs, and their relatives acquired a complete second set of genes. Scientists think this genome-wide duplication likely helped shape these species into the tallest, hardiest plants in the world. But it’s also made sequencing them an incredibly daunting challenge. And unlike corn and soybean, there hasn’t been much money available to even try. So far scientists have managed to put together partial DNA blueprints for only a handful of conifers, not including the most popular Christmas tree species.”

2) Scientists and researchers are studying genetic data taken from Christmas trees around the world to better understand the DNA of these trees and increase the potential for genetic improvement. For example, North Carolina State University’s Christmas Tree Genetics Program has been working since 1996 to advance the state’s Christmas tree industry through the application of genetic principles.
"We are doing DNA sequencing to understand the DNA of Christmas trees, and in the long term, this may lead in the future to genetic engineering." – John Frampton, professor in the department of Forestry and Environmental Resources at North Carolina State University

3) Genetics research could lead to the development of Fraser firs that are resistant to pests like Phytophthora root rot and the balsam woolly adelgid. A Christmas tree spends six to 10 years growing before it is cut to be sold, and such pests can kill a tree before that time.
Phytophthora is a fungus-like organism that can infect a Fraser fir and cause yellow-green needles, wilting, dead branches, and eventually tree death.

Balsam woolly adelgid is a small insect that feeds on Fraser firs and kills the trees after several years of infestation.

4) Genetics research is also exploring what separates the best needle-holders from the worst. Using branches from different trees, Gary Chastenger, a plant pathologist at Washington State University, has been researching the genetic variations of trees and needle retention. Via Wired:
Today, Chastagner’s team hangs the branches on racks or wire clotheslines strung across a temperature-controlled concrete cistern, where they rest without water for seven to 10 days. Then, a few well-trained technicians gently rub each branch and rate the needle retention on a scale of one (1 percent of needles fall off) to seven (91 to 100 percent loss).

Chastagner is only interested in the extremes on both sides of the spectrum. Over the years, he’s taken any cuttings that rate zero to one, or six to seven and grafted little bits of them onto rootstocks his lab manages on 15 acres in Puyallup. This process converts each outlying specimen into an isolated stand of genetically identical trees, preserving their unique DNA in what’s called a clonal holding block.

Now, those trees are part of a massive effort to pinpoint the tiny genetic variations that determine why some trees turn out better than others.

Six years ago, Chastagner and researchers at Washington State University, North Carolina State University and University of California, Davis jointly secured $1.3 million in funding from the U.S. Department of Agriculture to find genetic markers for Phytophthora root rot resistance and needle retention.
Chastagner’s graduate student, Katie McKeever, is collecting isolates of Phytophthora in various growing areas. By sequencing these samples and conducting pathogenicity trials, McKeever will contribute critical information to the team’s search for mechanisms of resistance in trees. Once the researchers find the relevant genetic markers, they can screen adult trees and select the most promising as seed sources for viable Christmas tree plantations.

The team will use similar techniques to resolve the matter of needle shedding. Chastagner’s multi-decade cataloging of Christmas trees with varying degrees of postharvest needle retention will give this part of the project a jump-start. By using these and other trees, scientists will be able to quickly identify needle-retentive gene sources so growers can produce desirable Christmas trees.

Through genetics research we can improve firs that are used for Christmas trees and ensure the genetic conservation of firs. There is much more to learn about conifer genetics, but as Chastagner said in the interview with Wired, “the potential for genetic improvement in these species is huge.”