Eucalyptus DNA blueprint revealed

By Beau Gamble 29 July 2011
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The Australian flooded gum is the world’s most farmed tree – and now scientists have unlocked the secrets of its DNA.

IN A MAJOR BOOST to global forestry research, scientists have mapped the genome of Eucalyptus grandis – the world’s most common plantation tree and one of our biggest eucalypts.

The flooded gum, also known as the rose gum, is only the second commercially forested tree ever to have its genome – its entire DNA sequence – decoded.

The genome map – developed by the US Department of Energy and the Eucalyptus Genome Network – will allow scientists to identify the genes responsible for rapid growth and other desirable traits. Essentially, the knowledge will fast-track the development of superior genetic varieties of flooded gum and other eucalypts.

“In the past, we would go out and select a range of different trees,
grow them up for twenty years and see how they perform,” says Professor
Bill Foley, a plant geneticist at the Australian National University and
a participant in the study. “But now we can shortcut that process and
understand exactly what makes desirable traits in a tree.”

Perfect plantation tree

The preliminary sequencing of the eucalypt genome was announced earlier
this year, but now scientists gathered in Melbourne this week at the XVIII International Botanical Congress are discussing all the possible research applications of the genome.

The flooded gum is grown all around the world, with millions of hectares of plantations in America, Europe, Asia and Africa.

“It has very good form – it grows as a tall, straight tree rather than a scraggly tree that wanders all over the bush,” says Bill. “It also produces good quality pulp, so it’s of interest to paper producers.”

In Australia, the species grows naturally along the coasts of NSW and Queensland, where it is harvested for furniture and timber for construction. But overseas, the focus is on growing the flooded gum for sustainable biofuel, helping to wean the world off its dependence on fossil fuels. “[The US Department of Energy] is thinking about eucalypts as a way to create fast-growing bioenergy crops,” says Bill, “because they produce so much biomass so quickly.”

‘Shotgun sequencing’

To map the flooded gum’s genome, the team used a process called ‘shotgun sequencing’, says Bill. “We basically bust [the DNA] up into lots and lots of small fragments.” The researchers then used sequencing machines to read the genetic code on each fragment.

“The problem is putting the jigsaw puzzle back together at the end,” he says. “It really challenges the amount of computer power we have to stitch it all together again.”

Dr Jason Able, an expert in plant breeding from the University of Adelaide, says that knowledge of the flooded gum’s genome will benefit research into other, similar species as well. “The implications of knowing the full sequenced genome of any plant are huge,” says Jason. “If you work on Casuarinas, for example, then you could go and look at the Eucalyptus genome – they share similar genes.”

With rapidly evolving DNA technologies, Bill says more Australian natives are likely to be sequenced in the next few years.

“The speed at which we can get the genome information is doubling about every six months; it’s even hard for somebody in the area to keep up with all the new technologies,” he says. “What we could do a year ago costs us about half as much now.”