Posted: Thursday, October 25, 2012 12:00 PM
Growers fear widespread public distrust of genetic engineering
Researchers at USDA have genetically engineered an apple with increased cold tolerance, but they don't plan on ever commercializing the cultivar.
Instead, they plan to study the genes responsible for the increased hardiness and then try to replicate the trait through breeding.
"My intention is not to produce a transgenic crop, by any means," said Michael Wisniewski, a research plant pathologist with the USDA Agricultural Research Service in Kearneysville, W.Va., who is working on the project.
The biotech apple cultivar relies on a genetic "transcription factor" from peach trees, which regulates the expression of other genes that allow plants to better withstand freezing conditions, Wisniewski said.
"You can think of this as a master switch, where you turn it on and all the light bulbs in the house go on," he said.
Wisniewski's goal is to study the biology of the transgenic cultivar and find out how to activate those genes without any external genetic material.
Achieving the same result with breeding will allow researchers to avoid jeopardizing the market for apples, since genetically engineered crops are still controversial with the public, he said.
"That's what the growers and the industry prefer at this point," said Wisniewski. "They don't want anything to blemish the image of the apple."
Researchers have been testing the biotech cultivar in the field for two years and recently obtained approval from USDA to continue field tests through late 2015.
Aside from improved cold hardiness, the cultivar also breaks bud later than other apple varieties, making it less susceptible to spring frosts that damage newly emerged plant tissue, Wisniewski said.
The cultivar's slower growth rate could also be an advantage, he said. "Everyone likes to have size control for high-density orchards."
Though researchers want to attain improved cold tolerance through breeding, they expect to drastically speed up the process with the help of another biotech trait.
Field tests have also been approved for another transgenic cultivar that uses genes from poplar and birch to impart "reduced juvenility," allowing apples to begin flowering after a year rather than four or five, Wisniewski said.
The time needed to develop new cultivars could be shortened from 20 years or more to about five years, he said. "It has tremendous potential."
Early flowering "segregates" in descendant plants, so only half of the progeny inherit the transgenic trait, said Ann Callahan, research geneticist with the agency.
The trait can be used to speed up breeding until it's no longer necessary, at which point researchers can select for plants without reduced juvenility, eliminating those genes, she said.
"It no longer has the transgene, technically," said Callahan, noting that the resulting cultivar wouldn't be regulated as genetically engineered by USDA. "It's not sidestepping the regulation. It doesn't come under the regulation."
The agency's Animal and Plant Health Inspection Service, which regulates biotech crops, confirmed in a letter last year that fruit trees bred with this method don't contain "inserted, transgenic material" and thus wouldn't be considered "regulated articles."
The technology is also being used in plum breeding and can be applied to "any kind of perennial plant, any plant with long juvenility," Callahan said. "It's a way to do some fast breeding."
The Northwest Horticultural Council, a tree fruit industry group, needs to learn more about this approach but is optimistic that the resulting cultivar would be considered conventional, said Chris Schlect, its president.
"That would seem to be a positive, and our industry would support it," he said. "It's not the same situation as an actual biotech apple."
Farmers currently use wind machines and other means to mitigate the effects of freezing temperatures, so better cold tolerance would be highly useful, he said. "I think there'd be very good use of the product."