Oregon hazelnut growers begin to benefit from the blight-resistant trees bred by OSU’s Shawn Mehlenbacher.
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n the field, in the lab, or travelling the world, Shawn Mehlenbacher concentrates on a singular goal: breeding hazelnut trees for all the best qualities and, most importantly, for resistance to eastern filbert blight, a disease that could put an end to Oregon’s valuable hazelnut industry.The Willamette Valley would look much different without Mehlenbacher’s work. Instead of the current rush to put land into hazelnut production, orchards would be dying, farmers would be scrambling to put in new crops, and the state would lose a valuable crop.
In 1987, a year after Mehlenbacher started his breeding program at Oregon State University’s College of Agricultural Sciences, Rick Burkemeier discovered eastern filbert blight in his orchard near Canby. He had just planted 130 acres of ‘Ennis’, a variety that’s excellent for market but extremely susceptible to EFB. It shook him out of denial.
“By 1994, it blew up; we had blight on every tree on the farm,” he recalls. “We pruned out diseased wood as best we could and sprayed with fungicide. I thought we were doing OK.”
That year, Burkemeier had a group of hazelnut growers to his farm. He shared a dour story of his war against eastern filbert blight.
“At the end of the tour, they drove off and I was standing there exhausted and discouraged,” he says. “Then Shawn walked up to me. He handed me his card with the name of three experimental varieties. He had a tear in his eye. ‘Here Rich,’ he said, ‘you may want to try these. They’re not immune, but they’re much better than what you’ve got.’”
Mehlenbacher’s generosity led Burkemeier to graft enough trees for 200 acres. He found one variety that did remarkably well. It was named ‘Lewis’, and he says it kept him in business. But by 2000, he started noticing blight in young trees. With a program of judicious pruning and spraying fungicides tested by Jay Pscheidt, professor and plant pathologist with OSU’s College of Agricultural Sciences, he’s been able to manage it as much as it can be managed. In the meantime, he’s replacing some ‘Lewis’ trees with newer disease-resistant varieties, but that requires patience. It can take almost two decades for a new cultivar to make it to market. And once planted, a hazelnut tree takes another four years to bear nuts.
Trees fighting EFB develop rows of elongated cankers, their branches begin to turn brown, and over a lengthy period of seven to 10 years, they succumb.
“Remember we’re dealing with a fungus that reproduces with an infinite number of spores spread by rain in winter,” Burkemeier says. “When you have 5 percent of an infinite number, it’s still an infinite number and that’s what we’re dealing with.”
Not only that, but the disease can mutate into new races of the fungi that the trees can’t fight off. On the East Coast, where the disease is native and has been devastating hazelnut orchards for more than 100 years, new forms of eastern filbert blight have already appeared.
Mehlenbacher, who has a doctorate in plant breeding from Cornell University, and his crew fight to stay ahead of these destructive fungi by keeping new trees in the breeding stream. Advances in genetics sped up the process by allowing him to determine in the lab whether a new seedling has immune genes. Instead of moving trees into the field where it takes years to determine resistance, they use a process called polymerase chain reaction to find DNA markers for immunity to EFB. As soon as the first leaves grow on the offspring, a piece is transferred to a petri dish of gel and analyzed under the electron microscope. The ability to check for eastern filbert blight at that early stage saves hundreds of hours that might be invested in moving or transplanting trees, and acres of land needed to accommodate them.
“We only had markers for the ‘Gasaway’ gene, the first variety found to be resistant to eastern filbert blight; now we have 100,” Mehlenbacher explains. “There are seeds from all over the world. As we studied them, we found which transmit resistance to their offspring. Sometimes none; sometimes 50 percent. So far, we’ve mapped a dozen different resistance genes. With markers, you can quickly identify which chromosome the gene is on.”
There are seeds from all over the world. As we studied them, we found which transmit resistance to their offspring. Sometimes none; sometimes 50 percent.
While the lab process speeds things up, trees still need to be evaluated in the field. EFB resistance is not necessarily a sign that the variety will succeed. The crosses are monitored for best characteristics, including yield, vigor, growth habit, nut size, and color; how easily the nuts let go of the husk; and how difficult they are to crack.
Traditionally, Oregon focused on the in-shell nut, or what’s called the “holiday nut bowl” version. But the market has shifted. Demand now calls for smaller nuts or kernels that are used in candy, cookies, and other processed foods. One of the biggest markets is Ferrero, makers of Nutella and the world’s largest buyer of hazelnuts. OSU and the company have been in talks in the past about Ferrero supporting research in exchange for breeding information. Although the negotiations fell though, Mehlenbacher says the door is open.
“We ended up with zero from Ferrero,” he says, “but we showed we’re the ones to come to about hazelnuts. Everyone does. We’re the largest breeding program in the world, bigger than all the rest put together.”
In four and a half years, Mehlenbacher plans to put aside his cracking hammer and retire.
“It wouldn’t have been the same if Shawn had not been here,” says Wayne Chambers, a grower since 1964. “It wouldn’t be much of an industry without him. It’d be pistachios, I guess. Hopefully, we can continue to utilize his services on a different level, as a consultant maybe. Will he stay in the game? He better.”