In 1997, one of the lab's graduate students attended a meeting of the American Society of Plant Biologists, and brought back a book containing hundreds of abstracts. "I was just looking through it," Powell recalled, "and I came across this abstract, the title of which was Expression of Oxalate Oxidase in Transgenic Plants Provides Resistance to Oxalic Acid and Oxalate-Producing Fungi."
Now that may not sound like much if you don't spend all your days thinking about chestnut blight, but to Powell, it struck a bell in his brain -- oxalic acid is the toxin that chestnut blight produces. "Immediately I thought, well, here's a gene that we could use in the chestnut." That gene came from wheat.
Powell reached out to one of the authors of that paper, Randy Allen at Texas Tech, who mailed him copies of the gene in a test tube. Back at the SUNY-ESF lab, they began by putting them into hybrid poplar (they still at that point were unable to genetically engineer chestnut). That worked, and they were able to increase the poplar's resistance to another fungal pathogen. "That kind of showed us, oh, this is a good gene to use," Powell said.
Over the next few years, Powell, his colleagues at ESF, and scientists at labs around the country made incremental progress toward their dream of a blight-resistant transgenic chestnut. In the early 2000s, they were first able to genetically engineer a chestnut embryo; the related paper was published in 2006 -- the same year the first transgenic chestnut was planeted outside of the lab. Following that they developed a line of chestnuts called Darling 4, which seems to be a bit less resistant to the blight than Chinese chestnuts, but still much better than a regular American chestnut. Last summer, they planted one of those trees at the New York Botanical Garden, not far from where the blight was first discovered.
The Darling 4 gets planted at the New York Botanical Garden. (courtesy of William A. Powell)
But they wanted even higher levels of resistance yet, and now they think they might have done it: a transgenic line of chestnuts, more resistant to the blight than even the Chinese trees. The team, lead by then-graduate student Amelia Bo Zhang, published their results in Trangenic Research in March. Earlier this month, they planted these trees at the Lafayette Road Experiment Station -- the first American chestnuts on this Earth that are highly resistant to the blight.
"Doing research on trees is just very difficult," Zhang told me. "The trees have very long lifespans. And it took a lot of researchers so many years to get to the point where we are today." Powell estimates that more than 50 different people at his and Maynard's lab have worked on this project over the last 23 years.
Powell is quick to emphasize that these results are preliminary, based on "leaf assay tests" which take place in the lab and are performed on small plants. "Working with trees is really hard because you have to get it to grow to a certain size. We really need to get it to be about two to three years old to do the final test to confirm that it is truly resistant," he said.