An expert from the University of Pretoria (UP) is part of an international team that will embark on a large-scale genome sequencing of 2 000 eucalyptus trees.

Professor Zander Myburg, Chair in Forest Genomics and Biotechnology at UP’s Forestry and Agricultural Biotechnology Institute (FABI), along with Prof Justin Borevitz of the Australian National University and Prof Jill Wegzryn of the University of Connecticut and their teams, will bring together vast experience in molecular genetics, genomics and computational biology. Prof Myburg is also the Director of the Forest Molecular Genetics Programme at UP.

The project proposed by the international team will be funded by the United States Department of Energy (US-DOE) through the Community Science Programme (CSP) of the DOE’s Joint Genome Institute (JGI) as part of the 2022 CSP call. The genome sequencing and analysis will be done at the JGI and other affiliated institutes.

Eucalyptus tree logs analysed by the Forest Molecular Genetics Programme. (Image: AA Myburg)

One of the aims of this effort will be to identify genes associated with growth and woody biomass production in these trees. “Eucalyptus tree species include some of the fastest-growing woody plants on Earth,” Prof Myburg explained. “In the process of growing wood, these trees remove carbon dioxide from the atmosphere. They store this carbon in the form of a renewable raw material (wood) that provides an alternative for fossil carbon products, including bioenergy and a large number of biomaterial and biochemical products (construction wood, pulp, paper, cellulose, textiles, pharmaceuticals and food additives). Understanding the genomes of these trees is essential for developing future woody biomass crops, which will be the feedstocks of the bio-based economy.”

We wear and eat wood products on a daily basis without knowing it, Prof Myburg added. Many textiles are derived from wood, including viscose, rayon and, more recently, Lyocell. And because cellulose is inert, it is commonly used in pharmaceutical pills in the form of microcrystalline cellulose fillers and as a food additive to increase viscosity in products like meat pies and ice cream. “Also, our toilet and tissue paper is derived from wood fibre, and everything we order from Amazon or Takealot is packaged in cardboard products derived from wood.”

Eucalyptus species are endemic to Australia and the islands of Indonesia (East Timor). There are more than 900 species of “eucalypts” (about 700 are from the genus Eucalyptus; the rest are Corymbia and Angophora).

Some collections of eucalyptus species are present in South Africa in gardens, arboretums, provenance trials and conservation parks established by forestry companies. Others are being conserved in South Africa because they are either inaccessible or threatened in their natural range.

“Thanks to the Atlas of Living Australia, a phenomenal resource, we have very detailed knowledge of the environmental conditions in which each of the wild populations (provenances) of Eucalyptus grandis have evolved and adapted,” Prof Myburg said. “We can compare the genomes and identify genomic diversity that is in common in trees that share adaptation to environmental factors such as temperature, rainfall, elevation and soil types across the natural range of the species (most of the east coast of Australia).

“Then, growing them in common garden trials in subtropical and temperate sites in South Africa allows us to compare their growth and woody biomass properties in the same and in contrasting environments, and to associate genomic variants to any differences that we observe among trees in these trials. We know what future environments are predicted for South Africa, and we can look at current environments in Australia that match those future conditions, such as hotter and drier climates. The trees that are already adapted to those extreme conditions likely carry genetic diversity that will be important to breed into our trees in South Africa as we develop tree crops for future climate scenarios.”

A eucalyptus plantation. (Image: AA Myburg)