This is an exciting time in the field of conservation and biotechnology. For the first time, it seems likely that a genetically engineered (GE) tree could be approved by US regulatory agencies for use in the restoration of an endangered species in the wild. This tree is the American chestnut, a species decimated by disease in the last century. Proponents of American Chestnut Restoration have waited decades for this day to come, and anticipation for its release grows stronger with each passing month.
Despite the enthusiasm of many for the chance to grow native chestnut again, some oppose the use of biotechnology for American chestnut restoration. A recent opinion piece in The Hill expressed the concerns of opponents of the release of blight-tolerant GM chestnuts, so I will attempt to address those concerns and provide insight into efforts to restore the American Chestnut. .
The American chestnut was once an important member of eastern American forests, but it was effectively lost to a fungal blight pathogen that made its way to the United States on its own. stop on resistant species of Asian chestnuts. Decades of research at the SUNY College of Environmental Science and Forestry in Syracuse, NY, have produced American chestnut trees called “Darling” that harbor an acid detoxifier gene from wheat, which allows trees to survive blight fungus infections.
This feat of modern biology allows the conservation of native chestnut genetics without hybridization with other chestnut species. Opponents of ‘Darling’ trees suggest that hybrid Chinese-American chestnuts would be a safer choice, citing concerns about unexpected changes that could come from the GM techniques used to create the blight-tolerant chestnuts.
While American chestnut trees bred with Asian chestnut species may have an increased tolerance to blight infections, many important native chestnut traits are also lost in the process. This is due to the huge genetic changes that occur when two species hybridize, where the entire genetic structure of the species is rearranged. In contrast, ‘Darling’ American chestnuts retain their genetic makeup with the small addition of the wheat gene. Additionally, the genetic sequence (genome) of ‘Darling’ has been mapped and no unexpected genetic changes have been caused by the addition of the wheat gene.
Another concern is the possibility that resistance to blight does not persist sufficiently over time and that the trees eventually succumb to the infections for which they were developed. While this is a valid concern, it is unlikely due to the way the wheat gene protects the tree without directly harming the fungus. Moreover, the end result of this scenario would be the death of the genetically modified trees, which is the same result currently experienced by wild trees. In other words, there is no additional threat, just an extension of the status quo.
While it is impossible to know all the possible consequences of planting ‘Darling’ chestnut trees in the forest, it is possible to exclude many hypothetical risks. For example, some of the most sensitive organisms in the native chestnut ecosystem include pollinating insects and amphibians, which suffer from even small exposures to toxins. Experiments were conducted where bumblebees were fed pollen containing the wheat gene and wood frog tadpoles were fed ‘Darling’ chestnut leaves. In both cases, no difference was observed between chestnuts with or without the wheat gene.
These are just two examples of environmental studies carried out with ‘Darling’ chestnut trees to test their safety. In all of these published studies that looked at interactions with insects, plants, fungi, amphibians, and more, no negative effects were observed from the additional wheat gene. Therefore, it is reasonable to conclude that these trees pose no new threat to the environment. This is not surprising, since the same gene used in ‘Darling’ chestnuts is found naturally in many species of plants and fungi that live in eastern forests and other ecosystems. After evaluating these studies as part of a multi-year review, the United States Department of Agriculture (USDA) also concluded that these trees do not pose new environmental risks. (The USDA’s public comment period on the trees ends December 27.)
The American Chestnut Foundation’s current approach is a multi-pronged strategy that uses biotechnology in conjunction with breeding and biological control techniques. The “darling” trees fall into the category of biotechnology, but there is also a decades-long breeding program that has incorporated Chinese chestnut resistance genes into late-generation hybrid American chestnut trees.
These two approaches are not considered as one proposition or the other, but as complementary techniques that can be explored in parallel, as well as in combination. The third category is biological control, which includes several techniques that lessen the damage caused by infection by treating infected trees with biological agents. Biological control helps maintain existing trees in orchards, but also has the potential to mitigate disease damage in wild ecosystems. The combination of these three approaches is known as 3BUR: Biotechnology, Breeding, and Biocontrol United for Restoration. A combined strategy has the best chance of success in American Chestnut restoration.
In an era filled with seemingly endless stories of environmental degradation, the potential restoration of the American Chestnut using biotechnology presents a clear example of the positive impact humans can have on the environment. environment. This tree may represent the first of many projects where people can help trees resist invasive diseases. But for starters, it will be the return of one of America’s most iconic forest tree species.
Erik Carlson is a research project assistant, teaching assistant and doctoral student at SUNY College of Environmental and Forestry Sciences and a member of the New York Chapter of American Chestnut Foundation.
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