Rose rosette, a virus spread by a mite the size of a speck of dust, has forced landscapers to destroy thousands of rose bushes in Dallas-Fort Worth in recent years. Counties in and north of the region have had hundreds of reports of additional cases, the most in a state that has a city, Tyler, that holds itself out as the rose capital of America. It has gotten to the point where those in the business have given up on planting the flower. That’s the case with Steve Huddleston, a senior horticulturist at the Fort Worth Botanic Garden who also owns a landscaping company.
Four years ago, the pathogen forced Fort Worth Botanic Garden to remove and discard all of the roughly 1,000 roses in its rose garden—the only method science has offered in decades for dealing with infected plants. The facility, which is on the National Register of Historic Places, has resumed planting roses, managing the condition by spacing the flowers farther apart with different plants in between, Huddleston says.
But a solution may be on the way from a Dallas-based research team, which used a $15,000 donation from the American Rose Society to create infectious clones of rose rosette emaravirus—potentially a starter kit for ending the epidemic. “If you can make a DNA copy of the virus that you can store in a laboratory, you can do reverse genetics, where you make mutations in the lab to identify the functions of its genes,” says Jeanmarie Verchot, a Texas A&M plant pathology professor who leads the effort.
“Breeders can only deal with natural infections,” adds Verchot, whose team includes two Dallas scientists and a pair of research groups in College Station. “I can now go into controlled greenhouses at my research center, infect plants, and see which become sick and which don’t.”
Rose rosette has caused as much as $50 million-plus in lost revenue nationally for growers since 2014, according to the Shreveport, Louisiana.-based Rose Society. Yet it remains a surprisingly unknown quantity. A&M’s David Byrne coordinates work at a half-dozen institutions nationwide, looking into resistance that some rose varieties may have to the disease. “Scientists discovered proof only in 2011 that a virus causes it, even though we had known about the ailment for 70 or 80 years,” he says.
This summer, Verchot and her team were preparing to submit their research to a scholarly journal, the way scientists get validation from their peers. That process, which she estimated could last six months, is the first step in raising funds for follow-up work, as other outside experts must read and approve it before publication.
The research could prove to be very important, says Mark Windham, a University of Tennessee-Knoxville professor who is part of Byrne’s project. “It currently takes three to four years minimum to determine which roses may resist the sickness. This may speed that up significantly.”
“Although techniques have improved for managing rose rosette, there remains a limit on what can be done now to keep the flowers safe.”
Scientists have cloned infectious viruses since the 1980s, both to understand their weak points and how they operate. But most of that work has focused on conditions that affect people. And where most viruses have one or two segments, rose rosette has seven, whose bulk is tough for scientists to cram into cells to start infections for research. “It’s a lot of material to work with,” says Verchot, whose team developed technology for getting that job done that they are now trying to patent.
To track how rose rosette infection moves within given species of roses, her researchers are modifying an existing trick: Sticking green, fluorescent molecules called proteins inside the pathogen’s genome, which carries its seven known genes that contain its blueprint. By inserting into roses the virus cells containing glow-in-the-dark proteins, researchers can track where the bad guys go by holding an ultraviolet lamp over the plant. The team is optimizing this system for different varieties of roses.
The new ability to infect roses for research dovetails with improvements that the roughly 28 researchers in Byrne’s group have made to a method for determining which varieties may withstand the ailment.
Much like Verchot’s team uses glowing proteins to follow virus’ paths, Byrne’s group tracks pieces of roses’ DNA ladder that are associated with traits they want to encourage, such as the ability to withstand both rose rosette and black spot, a fungal disease that experts say weakens them by making their leaves fall off. This research tactic is called using “molecular markers.”
“Even five years ago, we only had a couple hundred markers to work with,” Byrne says. “Now we have thousands. Of the 1,200 rose ascensions that we’ve looked at for the microbe maybe 20 might be resistant.” That, coupled with faster diagnosis of the infection, is speeding up the process of determining which rose breeds might best weather problems like the emaravirus. “It’s a three-year process in the field,” Byrne says. “If [Verchot] can do it in a greenhouse, we might be able to cycle that down to three to six months.”
Questions About Commercialization
As Verchot and her team work on the scholarly article and seeking patents for their inventions, they are also tackling a larger issue: How to bring their creation to market. They’re partnering with commercial growers around the country and letting them drive the commercialization. Verchot, who came to Dallas two years ago from Oklahoma State University in Stillwater, is incorporating her experience running a startup centered on protective technology for canna lilies, decorative flowers that can resemble irises. “Based on what I learned before, I’m trying to take a strategic approach,” Verchot says. “I may want to develop a different model than I did before.”
To be sure, even the president of the Rose Society, which funded the virus-cloning research, is skeptical that scientists can achieve the holy grail of emaravirus-resistant roses. “I’m not optimistic,” says Robert Martin, whose organization has focused on educating the public and reporting.
Scientists have their work cut out for them. A Tennessee test found that just 4 percent of some 1,200 rose varieties may be able to withstand the emaravirus, according to Windham, the Knoxville professor. “But they’re not what people will want in their yard,” he says. “We must get the resistance out of them and put it into others that people desire.” Windham is looking for weak points on the mite that transmits it, and aims to use as little pesticide as possible to achieve maximum effects.
Verchot, meantime, is working on grant requests to turn her starter kit into a toolbox over the next years. The money could allow for hiring additional scientists to help determine what each of the virus’ known seven genes do and how mites acquire and transmit it. “We’re exploring publishing a new paper about gene-editing technology we’re developing for potatoes,” she says. “If we can use it for enhancing plants’ own ability for protecting themselves from rose rosette, that would be huge.”
The virus-cloning system might also work with rose rosette’s eight cousins. “One of them, the High Plains virus, has been a major issue for wheat production throughout the Great Plains,” Verchot says. “We’re just at the beginning with a starter kit. Now we must write a grant to build it into something more robust.”
Despite the progress, the unfortunate reality for commercial and residential growers is that although techniques have improved for managing rose rosette, there remains a limit on what can be done now to keep the flowers safe. “There have not really been any new methods that prevent it,” says Dave Forehand, vice president of gardens at the Dallas Arboretum. To lower the chance of spreading the disease, the Arboretum has reduced the number of roses on display, he says. “We carefully monitor the remaining ones for any signs of rose rosette. If found, we immediately remove and discard the plant.” The good news is better days may be ahead because of scientists’ improving understanding both of the virus and roses themselves.
Jeff Bounds is an award-winning business writer based in Garland.