Good Fruit Grower

February 15, 2017

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14 FEBRUARY 15, 2017 GOOD FRUIT GROWER N ew Jersey's tiny wine industry is booming — as are local wineries across much of the Eastern U.S. — but grape growers in those regions face increased disease pressure from fungi such as downy mildew that thrive in the humid conditions. That's why a plant pathologist at Rutgers University is experimenting with a cutting-edge tool to basically turn off the genetic welcome mat in the grape's DNA that allows the downy mildew fungus to take hold. If success- ful, the research will create Chardonnay grapes that resist the pathogen and that could hopefully be grown without dependence on intensive fungicide application. That's very appealing to some of the region's grow- ers because winemakers are often concerned about how pesticide residues may impact fermentation, said Dan Ward, director of the New Jersey Center for Wine Research and Education. Currently about 200 wine grape growers, working over 2,000 acres in New Jersey, rely on careful canopy man- agement to allow air circulation and light penetration to combat wet conditions that encourage fungal disease, Ward said. Even with those techniques, Eastern U.S. grape growers are completely dependent on fungicides to prevent downy mildew and other common diseases from destroying crops and eventually killing the vine- yards. That's why Ward is excited about the potential of engineering resistant grapes. "I brought it up at (industry meetings) and the peo- ple who responded were excited by the prospect of a genetically modifi ed grapevine being available to them to reduce the need for fungicide," Ward said. "There is interest among some of our larger grape growers, who were immediately warm to the idea of modifi cations to an existing variety — preserving the qualities that make them valuable while eliminating the qualities that make them susceptible." No open window for mildew Rong Di, a professor of plant biology at Rutgers, is growing tiny mutant plants in her lab that are resistant to the fungal pathogen. But she's not actually growing grapes yet. She started to test her theory that turning off the genes that serve as "host factors" for mildew would create disease resistance in an extremely well-studied little mustard known as Arabidopsis, which serves as a model in lots of genetic research. These host factor genes basically give each specifi c fungus the ability to interact with and infect the host plant, Di said. To turn them off, she's using a gene editing tool called CRISPR. Praised as a biotechnology breakthrough, the powerful tool has been adopted by scientists around the country for its precise and effi cient ability to edit the DNA of any organism. "I'm always on the lookout for new technology, so three years ago when the CRISPR gene editing came out, Cutting-edge technique to keep pathogens away Special Report: Disease Resistance Rutgers researchers hope gene-editing technology can make wine grapes resistant to downy mildew. by Kate Prengaman How gene-editing is altering the GMO debate A gene-editing technique known as CRISPR can make precise genetic changes without transferring DNA from other species. That means crops altered using the procedure are not expected to be subject to current U.S. Department of Agriculture regulations or labeling requirements. But whether consumers will support it remains to be seen. Here's how it works: Scientists target a specifi c site in a DNA strand to be edited. Sequence to be edited Scientists then pair an enzyme and a "guide RNA" sequence. The guide RNA lines itself up with the sequence to be edited, where the enzyme makes a precise cut. A new DNA piece, supplied by the scientists, fi lls in the new gap in the strand created after the cut. "Guide RNA" "It's very targeted; we can direct the DNA endonucleases where we want so we don't have to hurt the plant in other ways. We only knock out the gene I choose." —Rong Di

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