Save the roses

With the help of a $4.6 million award from the USDA last fall, researchers have set in motion a number of efforts to thwart the deadly and costly rose rosette disease (RRD). The funds were matched by $4.6 million of in-kind and cash contributions from growers and breeders both big and small, as well as some major landscape companies, says Mike Dobres, managing director of NovaFlora LLC, the research and breeding division of Star Roses and Plants/Conard-Pyle. The funds will be used to develop best management practices, expand outreach and education efforts, and to map genes for RRD resistance in roses.

RRD is a virus that is transmitted by the mite Phyllocoptes fructiphilus, and RRD threatens to decimate the U.S. landscape rose industry. The disappearance of this genus in the nursery industry would remove some $400 million in domestically grown plant sales, according to Star Roses and Plants/Conard-Pyle.

The research funding represents the culmination of a two-year initiative originally conceived and funded by Star Roses and Plants/Conard-Pyle to reach out to key university researchers and industry leaders to respond to the serious threat that RRD represents. Dobres has led the charge in many of the initiatives of the past few years regarding RRD.

“This research team is a wonderful example of the collaboration between the university and horticulture worlds, as well as within the industry with various companies coming together to support this effort,” Dobres says.

The grant enables the next wave of RRD research to have three main objectives, he adds.

“One, we’ll further develop diagnostic tools. Second, we’ll learn more about how the disease spreads and develop cultural recommendations, and third, we’ll map the rose genes for disease resistance,” he explains.

Dobres describes the research team as the “dream team,” which is led by David Byrne, Texas A&M AgriLife Research horticulturist and holder of the Basye Chair of Rose Genetics in College Station. The research group working with Byrne was selected from five leading university and government research centers with a wide geographic distribution, ranging from Texas to Florida, Oklahoma, Delaware and Maryland. The research team includes more than 20 scientists with expertise in plant pathology, DNA detection technologies, genetic mapping and rose breeding. The group also includes industry partners such as major growers and commercial breeders throughout the United States.

“The beauty of this research approach is that it combines both short-term cultural solutions as well as long-term solutions to breed roses that are resistant to RRD,” Dobres says.

Diagnostics is the major push during the first two years of this collaborative research, says Byrne.

“We currently have a lab test to detect the disease, but it’s expensive and slow. Currently we can only detect RRD in a plant that shows symptoms. We want to change that. But the problems is that we don’t understand much about the virus once it’s in the plant. Is it systemic? Is it going to the roots immediately? We need to concentrate on better methods of detecting it and the epidemiology of the disease,” Byrne explains.

Three groups are working on diagnostics and all are taking different approaches, says Byrne. For example, Ioannis E. Tzanetakis, associate professor of plant virology at the University of Arkansas, is researching the mite and the transmission of RRD.

The next major goal of the research team is to produce RRD-resistant germplasm, Byrne says.

“Roses react differently to the virus, and we don’t know anything yet about the garden varieties’ resistance to RRD,” he adds. “I’m a plant breeder, so I’m trying to find a source of resistance and put that into the cultivated material. I’ve acquired 300 different varieties and species to evaluate for resistance in Tennessee and Delaware, where there’s a lot of disease pressure.”

There are reports of two species that show resistance to RRD – Rosa palustris (swamp rose) and R. setigera (prairie rose), Byrne says. Mark Windham at the University of Tennessee and Tom Evans at the University of Delaware are doing the initial evaluation, he adds.

Byrne also is working with private rose breeders from across the country who are diligently looking at resistant varieties. Byrne says it will be a couple of years before crosses can be evaluated.