Eucalyptus DNA helps search for super-trees

PARIS (AFP) - Scientists said on Wednesday they had unravelled the genome of a eucalyptus tree, gaining insights into its fast growth and adaptability that could one day enhance forests grown for biomass and timber.

Eucalyptus is native to Australia, but has become the most widely-cultivated hardwood tree; an important source of paper, wood and essential oils grown in more than 100 countries on six continents.

It is are also considered a potentially major source of biofuels.

An international team of scientists have now sequenced the genetic code of one of the most widely-bred species: Eucalyptus grandis.

"We were interested especially in understanding its ability to produce very high cellulose-content wood, which is what makes it desirable for pulp and paper production," explained study co-author Alexander Myburg of the genetics department of the University of Pretoria in South Africa.

"We were able to identify almost all of the genes involved in converting sugars into cellulose... in the tree and also the other main component of wood which is lignin," he said in a podcast carried by the journal Nature, which published the study.

"These are important pathways to understand because they are the main components that will be used in terms of biofuels and other biomaterials that are harvested from woody biomass... trees." The team found the Eucalyptus grandis genome contained just over 36,000 genes, "an average, medium-sized plant genome".

It also contained the largest number of tandem duplications - two identical sequences, one following the other, in a chromosome segment - than any other plant genome sequenced so far.

Myburg said the findings may prove valuable in understanding how to boost the cellulose content of trees, but also how to extract it more easily.

Cellulose, basically a long string of glucose molecules, can be broken down to sugar and then fermented into biofuels, for example.

"The prospect of accelerating breeding cycles for productivity and wood quality... is enhanced by the release of the Eucalyptus genome," the authors wrote.