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To sequence a genome, scientists start by chopping DNA into small bits, and let their machines sequence each bit. That’s the part that has become much faster and cheaper in recent years. But then comes the task of re-assembling these bits back into the long DNA chains found in trees. And that is a huge challenge with conifers, because their DNA chains contain many repeated sequences that make the assembly a lot harder.

As a result, conifers present “these large regions I think we will never be able to piece together” with current technologies, said Par Ingvarsson of Umea University in Sweden, who is leading the Norway spruce project.

Will scientists develop new technologies to overcome that problem?

“You should never say never in this game,” Ingvarsson said.

This past summer, Neale’s group presented partial results for the genome sequence of loblolly pine, based on DNA extracted from a single pine nut. It includes about a million disconnected chunks of DNA, and altogether it covers well over half the tree’s genome.

Neale figures it will take his team until 2016 to complete genomes of the loblolly, Douglas-fir and sugar pine. The project is financed by the U.S. Department of Agriculture.

Mackay’s group recently released its early results on DNA taken from a single white spruce.

As for the Swedish project on Norway spruce, Ingvarsson said its results will be made public early next year. The 2 million DNA pieces have captured most of the estimated 35,000 to 40,000 genes in the tree, even if researchers don’t know just where those genes go in the overall genome sequence, he said.

People have about 23,000 genes, not much different from a conifer. The tree’s genome so much bigger because it also contains an abundance of non-gene DNA with no obvious function, Ingvarsson said.

He said his chief reason for tackling conifer genomes was to fill a conspicuous vacancy in the list of sequenced plants.

“It was like the one missing piece,” he said. “We just need this final piece to say something about how all the plant kingdom has evolved over the last billion years or so.”

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Online:

Canadian project: http://bit.ly/UQdTPd

U.S. project: http://pinegenome.org/pinerefseq/

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