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By Fred Miller
U of A System Division of Agriculture
Media Contact: Ryan McGeeney
[email protected]
501-671-2120
June 9, 2017
Research pursues resistance to rosette virus in roses
Fast Facts:
 Division of Agriculture researchers identified a virus in 2011 responsible for rosette
disease in roses.
 New research may have identified a rose genotype with resistance to the virus.
 Resistance offers the best defense against a disease that’s difficult to control.
(674 words)
(Art available for download at https://flic.kr/s/aHskWgkj5W.)
FAYETTEVILLE, Ark. — University of Arkansas System Division of Agriculture scientists have
identified a rose genotype that resists infection by the rose rosette virus, a pathogen that
disfigures and kills rose plants.
“Genotype” refers to the genetic code of an organism, and identifying this particular variation is
an important first step in developing new rose varieties with resistance to the disease, said
Ioannis Tzanetakis, associate professor of plant pathology.
Alma Laney and Patrick Di Bello, graduate students in Tzanetakis’ laboratory, discovered the
virus, developed sensitive detection tests and proved that the rosette virus is the sole causal
agent of the disease.
Since then, Tzanetakis said, researchers at other institutions have built on Tzanetakis’ work to
develop even more sensitive tests.
The discovery of the virus and development of the diagnostic tests have been breakthroughs for
the ornamental plant industry, Tzanetakis said. Commercial plant propagators can screen for
the virus and destroy plants that have the disease before it can spread to healthy rose plants.
More recently, Tzanetakis, Di Bello and post-doctoral research associates have been pursuing
resistance to the disease. They found one rose genotype out of many that didn’t get sick when
infected with the virus, Tzanetakis said.
“Under greenhouse conditions,” he said, “it cannot be infected.”
Traditionally, some gardeners cut off branches with disease symptoms, believing that would
keep the virus from spreading to other parts of the plant. But Tzanetakis said a simple test
showed the virus was present in the roots of an infected plant. “So, pruning doesn’t necessarily
remove the disease,” he said.
The discovery of a resistant genotype offers a more effective defense against infection and
provides a good starting point to breed resistance against the virus in popular varieties,
Tzanetakis said.
“Stable resistance is the best line of defense,” he said.
Knowing the rose has resistance is just the beginning. Tzanetakis said they don’t know where
the resistance is located in the plant’s genetic code. Also, because viruses change to adapt to
changing conditions, resistance must continually be sought out by plant breeders.
“It’s a good thing to look for,” Tzanetakis said. “But it’s hard work.”
To learn how the disease spreads, Tzanetakis and his research team looked at mites. Rose
rosette virus is one of a group of viruses that is known or suspected to be transmitted by mites.
Tobiasz Druciarek, a post-doctoral researcher on Tzanetakis’ team, is an acarologist — a
specialist in mites. He provided evidence that the virus replicates inside the vector, a disease
transmitter, called Phyllocoptes fructiphilus.
That means that once the mite has picked up the disease, it will continue to transmit it
indefinitely whenever it feeds on a rose plant.
Tzanetakis said previouse research from West Virginia has shown that infected roses have an
average of 17 times more mites on them than uninfected plants. This suggests that the virus
knocks down the plant’s natural defenses, allowing the mites to flourish.
It takes five days once an infected mite begins feeding on a plant until the plant becomes
infected with the virus,Tzanetakis said.
“This offers a window of opportunity to eradicate the mites before infection begins,” Tzanetakis
said.
The mites are microscopic and cannot be seen with the naked eye. But the mite hides on the
plant under the sockets where leaves are attached to the stems. Knowing where to look means
plants can be tested for the mites’ presence.
Unfortunately, chemical pesticides do not provide very effective control for the mites, Tzanetakis
said.
None of the plants in their tests had resistance to the mite, Tzanetakis said. Even the plant that
resisted the virus sustained a good mite population.
“This supports the idea that resistance to rose rosette virus is on the molecular (DNA) level,”
Tzanetakis said.
About the Division of Agriculture
The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture,
communities, and families by connecting trusted research to the adoption of best practices.
Through the Agricultural Experiment Station and the Cooperative Extension Service, the
Division of Agriculture conducts research and extension work within the nation’s historic land
grant education system.
The University of Arkansas System Division of Agriculture offers all its Extension and Research
programs to all eligible persons without regard to race, color, sex, gender identity, sexual
orientation, national origin, religion, age, disability, marital or veteran status, genetic information,
or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.
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