In a July 2011 photo, Kurt Laffin of Hudson pollinates a chestnut tree in Merrimack. The flowers were manually pollinated with pollen from a chestnut hybrid, then covered with bags to keep out other pollen. At the end of summer, the chestnuts are harvested and then planted to created the next generation of hybrids, whose pollen will be used in subsequent years.
Genetically modified chestnut trees might return this giant to our forests, faster
Posted by David Brooks | Thursday, June 12, 2014
After the American chestnut tree was virtually wiped out by an accidentally imported fungus, attempts began to breed a resistant variety by cross-breeding the few remaining samples with Chinese chestnuts, as I've often reported. Similar efforts are being used to create a resistant elm tree.
But there's another angle being pursued to develop resistant chestnut trees - genetic modifications. As New Scientist reports:
At State University of New York in Syracuse, the team has used genetic engineering to create a strain of fungus-resistant chestnuts called Darling4. The modified trees contain a gene from wheat called OxO, which makes an enzyme called oxalate oxidase that destroys the toxic oxalic acid made by the fungus, preventing cankers from forming on the tree. By-products from the enzyme's action help the tree's own natural defences to fight off the fungus.
The best news is that the resistance seems to be heritable through the chestnut seeds. This will make restoration simpler and faster, because growing trees from seedlings is faster than the current practice – growing trees from tissue-cultured plantlets derived from embryos found in the few surviving trees.
So far the GMO version is doing better at fighting the fungus than native trees, although not better than Chinese chestnuts.
If it improves, it will present an quandary for anti-GMO environmentalists: We need all the forest biodiversity we can get, especially since our ash trees are doomed by emerald ash borer and hemlocks are threatened by wooly adelgid beetles. If a GMO chestnut proves more viable than a cross-bed chestnut, should it be used in the wild?