Tree DNA: from sex to violins

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Martin Fairbank
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A few years ago I was at a roadside viewpoint in Utah looking at a slope covered with poplar trees  whose leaves were starting to turn yellow in the cold October air. An interpretive panel pointed out that while different shades of yellow could be seen in different groups of trees, all of the trees in each grouping were exactly the same shade of yellow.

The reason for this is that poplar trees can reproduce asexually through their root systems, essentially cloning themselves so that all the trees in a group have the same DNA. This means they react in exactly the same way to the temperature drop that occurs each autumn.

Most trees make new trees through sexual propagation. The pollen of one flower blossom is deposited on the stigma of another, and seeds are produced. This can occur in poplars, but is more difficult because they are unisexual, i.e., a tree is either male or female, and therefore a cloned poplar stand would all be of the same sex.

Like dairy cattle or racehorses, trees can be bred for superior characteristics, and this strategy has been adapted by Brazil for eucalyptus trees over the last forty years. Hybrids have been bred for characteristics such as disease resistance, better wood quality and faster growth, and then the resulting hybrids are cloned for plantation forestry. As an example of the success of this strategic breeding program, the yield of eucalyptus plantation wood in Brazil has increased from 27 m3/ha/year in the 1980s to 44 in 2015.    

With my background in chemistry, I tend to think of trees as containing only cellulose, hemicellulose and lignin. Between the old wood and the bark, however, is the living part of the tree, the cambium, where new wood grows and the DNA of the tree resides. A tree’s DNA can be determined today from about 2 g of sawdust from its outer edge. As any fan of TV shows such as CSI would know, DNA testing can now be performed rapidly on human suspects and compared with evidence from a crime scene. Available since 2010, automated rapid DNA testing of humans can produce results in about 90 minutes from a buccal swab, a test that previously took weeks or months. This has resulted in much higher efficiency in criminal justice systems for proving guilt or innocence.

For the first time in 2021, DNA testing of an individual tree was used to apprehend an illegal logger. Justin Andrew Wilke and a crew of associates were found to have conducted an illegal logging operation in the Olympic National Forest in Washington state, USA, between April and August 2018. The group removed highly prized maple trees, used to produce musical instruments such as violins and guitars, and forged permits to sell the wood. At the trial, testimony was presented showing that the wood sold by Wilke was a genetic match to the remains of three poached maple trees discovered in the forest by investigators. The DNA analysis was so precise, the probability of the match being coincidental was approximately 1 in 1 undecillion (1 followed by 36 zeros). Wilke was handed a 20-month prison sentence in November 2021, ordered to forfeit the proceeds of his illegal poaching and required to pay restitution to the U.S. Forest Service. A victory for tree science, and a new weapon to protect sustainable forestry!


Martin Fairbank, Ph.D. Martin Fairbank has worked in the forest products industry for 31 years,
including many years for a pulp and paper producer and two years with
Natural Resources Canada. With a Ph.D. in chemistry and experience in
process improvement, product development, energy management and lean
manufacturing, Martin currently works as an independent consultant,
based in Montreal. He is also an author, having recently published
Resolute Roots, a history of Resolute Forest Products and its
predecessors over the last 200 years.


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