Nation’s researchers team up to improve, protect roses

COLLEGE STATION — People should be able to stop and smell the roses, not spray them, said Dr. David Byrne, Texas A&M AgriLife Research rose breeder in College Station.

Byrne is part of two national specialty crop research projects aimed at toughening up roses’ ability to ward off diseases and other pestilences. He cited surveys in which the gardening public said the No. 1 desired trait is disease resistance.

“And I agree with them. That’s what I prefer,” Byrne said. “I don’t want to spray my roses.”

The first project, called RosBREED II, is a five-year effort by researchers studying a number of major fruit crops and roses. Byrne explained that the internationally loved flower is kin to apples, peaches, pears, strawberries, blackberries and cherries as part of the Rosaceae family.

Dr. David Byrne, Texas A&M AgriLife Research rose breeder, with roses in plots at Texas A&M University. He is collaborating on two national studies to develop rose varieties that are resistant to diseases such as black spot and rose rosette.

“In the fruit trees portion of that project, they’re talking about fruit quality or disease resistance,” he said. “In the roses, we’re talking about disease resistance, basically black spot.”

Byrne said researchers have longed for molecular markers that point to black spot resistant genes so they could be identified in the breeding process.

“We can use the tools that we have now basically to find tags on chromosomes that mark traits,” he said. “This helps us select the parents, because we know which ones combine best to get the maximum black spot resistance. It also helps us select some of the seedlings that are going to be best, and that helps us select seedlings quicker.”

Byrne explained that the traditional process would be to produce the seedlings, plant them in the field and then evaluate them over two or three years.

“If I had a marker that would tell me which genes a seedling had, I could select the ones that have black spot resistance in the first year, saving a couple of years,” he said. “I can do two generations with markers as fast as I can do one generation without markers.”

Along with Dr. Stan Hokanson at the University of Minnesota on the rose portion of the project, Byrne is studying progenies with different types of black spot resistance.

“The ultimate goal is to combine different types of resistance into one plant, because sometimes a plant can be moved around the country and be resistant in one place but not the other,” he said. “The reason is that the pathogen, the disease, is changing. Just as everybody is not identical within the human race, the individual fungi types of the pathogen are not identical either. They respond differently to plants. One type may be able to get around the defenses of one plant whereas the other won’t. Even though it’s the same disease, there are different siblings.”

He hopes to have some markers within the five-year effort so that a progressive breeding effort will quickly begin producing resistant rose cultivars.

“With this technology, maybe we could essentially transform all the rose varieties to those that are resistant to disease — and not just well known diseases such as black spot but also to upcoming diseases such as rose rosette.”

The emerging malady, rose rosette, has become such a devastating disease in many states that a second, five-year national research effort by some 20 scientists is targeting that disease specifically, said Byrne, who is leading the breeding component of that project.

“In this second project, we are also developing markers in trying to understand the rose rosette resistance, which we don’t know much about at the moment,” he said. “The first step is doing a lot of screening for rose rosette resistance.”

His collaborating researchers at the University of Tennessee and the University of Delaware, will provide Byrne with information on the disease — because it already exists in those states — so that he can do genetic studies at his College Station lab. His Texas team also can produce the progenies.

“I’m working with five commercial breeders in developing these progenies,” he said.

One major aspect of the rosette project pertains to diagnostic procedures, he noted, because the disease is a virus that was only recently discovered in 2011. It is transmitted by the tiny Phyllocoptes fructiphilus mite which floats in the air and cannot be seen by human eyes without magnification, making it very difficult to control, Byrne said.

The disease causes excessive thorn production, leaf distortion, excessive branch development at the ends of branches and ultimately death of the plant. It has been found in landscape roses in many states and is thought to have spread via wild roses.

“We’re trying to develop a diagnostic technique that is reliable and can be done in the field to decide whether a rose is infected,” Byrne said. “By the time we’re through with this project, we will have gone through a set of analysis to understand the inheritance of resistance and hopefully to find markers to tag it. We will be at the point to start breeding for it in a more efficient manner and commercial breeders, with whom we are working, will have this available to them.”

He said it would take an additional five or 10 years before varieties are available to consumers.

“There are so many different types of landscape roses that it is not just one rose that has to be converted. There are a dozen different types of roses, and each has all the different colors, so about 50-60 varieties would need to be bred with the resistance,” Byrne said.

Another facet of the project has established a monitoring network headed by Dr. Kevin Ong, Texas A&M AgriLife Extension Service plant pathologist, who has about 100 gardens throughout the U.S. checking monthly for rose rosette.

“This is helping to track where it is, how quickly it is moving and what varieties it’s on,” Byrne said. “The aspect of understanding the biology is very important, and we have a group working on that as well as a group that is focusing on the economics and marketing aspects of the impact of rose rosette and black spot on the rose industry.”

Byrne provides update on rose research, which is funded by the U.S. Department of Agriculture-National Institute of Food and Agriculture, on Facebook at https://www.facebook.com/tamuroses.