How mapping tree genomes can help plant forests resilient to climate change

A research team at the University of Alberta is looking into why some trees in Alberta are more resilient when faced with drought, disease and the risk of wildfires by sequencing tree genomes. 

A genome is the genetic makeup of an organism, and the thought behind sequencing tree genomes is that it’ll help inform what trees have a better chance of surviving in tough conditions, and what trees should be planted when reforesting areas lost to wildfires. 

The genome Alberta resilient forests project, led by U of A agricultural, life and environmental science faculty professor Barb Thomas, originally studied the genetic makeup of trees to determine what makes a resilient forest.

Now, they are using that data to map out the genome for pine and spruce trees. 

“What we typically are trying to do is to measure populations and make assessments and measurements … about what would be the best parents to use to produce progeny that could then be used for reforestation,” Thomas said. 

To determine this, Thomas’s team is studying more than 5,000 trees, measuring up to 30 different traits or phenotypes, so they can figure out which tree families are more resilient in Alberta’s climate. 

Some of the phenotypes they are looking for include height, density, the rate at which the tree grows and how they adapt to drought. 

“You can take that phenotypic information and you can build a model that links that to the genotype … that will help you determine whether or not [tree families] are more robust or not for whatever challenge you’re looking at,” said Thomas. 

WATCH | U of A researchers mapping tree genomes: 

She says this can be used to account for issues common to Alberta, including drought. 

“If you have measures of drought tolerance … you can map that onto that genotype, then you can make better decisions about which parents to keep,” said Thomas.

While genomic selection has been used by tree breeders to isolate certain tree families, mapping out a tree’s genome is a much more laborious process. 

Tree genome larger than human 

When the national human genome project was launched in 1990, it was seen as an ambitious project that would forever change the way we look at genetics. 

But when the project wrapped in 2003, the team of international researchers only successfully sequenced 92 per cent of the human genome. 

For the team at the University of Alberta, the challenge they face when sequencing tree genomes is the size of the genome itself. 

The human genomes includes 23 chromosomes, which are made of about three billion base pairs. Overall, humans have about 25,000 genes. 

Trees have fewer chromosomes, but they are much larger. 

“Just to give you a little bit of context … conifer genome on average is about 20 billion base pairs, so seven times larger than the human genome,” said Charles Chen, associate professor at Oklahoma State University, who is a partner in the project. 

He expects the conifer genomes to have up to 65,000 genes. 

“To me, I like to read genomes as basically a DNA language manual book,” said Chen. “To understand this manual book of genomes constitutes the first step to actually utilize the genetic variation to fight … disease or climate change.” 

Tree genomes will also help the forestry industry determine what family of trees grow faster and larger, says Chen. 

Reforesting with climate in mind 

Sequencing tree genomes can help determine where certain trees will thrive, but as the climate changes, and drought conditions continue to creep northward, this may become more difficult to do. 

And Thomas says Alberta has its own challenges. 

“Alberta is a very complicated province to work in, we have many challenges. We have the foothills, we have the plains, we have the boreal,” said Thomas. 

“There are different populations of these species in each area, it’s important to make sure that you’re testing [trees] where [they] could be moved in the future.” 

Once the spruce and pine genomes are sequenced, tree breeders and Alberta Forestry and Parks, can figure out which tree families are best suited for Alberta. 

“We could identify genetic factors responsible for better drought resistance, for example, and then they will actually give us a target that breeders of the government need to maintain those,” said Chen.

“Then [the sequence] will actually give us a target that breeders of the government need to maintain … to select for those genetic elements.” 

Currently, where trees can be planted depends on the province’s seed zones, but Thomas says the province may soon have to pivot to a climate seed model, and trialling different types of trees in the province. 

“We need to be proactive and be looking at bringing other species, like we have Douglas fir growing in this province … maybe there’s an opportunity for Douglas fir to be tested more thoroughly further into this province,” said Thomas. 

“What about ponderosa pine? Ponderosa pine is very drought tolerant, it’s quite fire resistant.” 

And it’s not just in Alberta that entire forest ecosystems might change as a result of climate change. For Chen, who lives in Oklahoma, he says the climate of the state is starting to feel more like neighbouring Texas. 

“Living in the South, we already see Oklahoma is not going to be Oklahoma in the next five years … [it] will be like northern Texas very, very soon,” said Chen, who says that state is much hotter and drier. 

“All the climate that we know … it’s not going to be the same in a very short time.” 

The Genome Alberta Resilient Forests project is only in its early stages, but is already getting a lot of attention from the province and timber industry. 

“We are working to understand the impacts of the changing climate on the forest and are supporting research into the genetics of trees that appear to be better adapted to the future climate,” wrote Richard Briand, chief forester for West Fraser’s Alberta branch, in a statement to CBC News. 

“West Fraser sees this knowledge as essential to ensuring healthy, resilient, productive forests remain present across the areas we have the privilege to manage across Alberta.”