Imagine a world where you never had to worry about viral infections plaguing your precious rose garden. Tissue culture techniques have successfully eliminated viruses in roses for decades. And with cutting-edge developments made by scientists at institutions like UC Davis, more and more virus-free roses are becoming available throughout the US.
Most Common Rose Viruses
The two most common viruses that infect roses every year are rose mosaic virus (RMV) and rose rosette disease (RRD).
RMV usually manifests itself on the leaves of your roses. Telltale signs include:
- Yellow veins
- Yellow zigzag patterns or ringspots
- Very faint swirls or squiggles
Signs of RRD include:
- Excessive thorniness
- Abnormal stem thickness or elongation
- Red or yellow mottling on the leaves
Once a rose is infected with RMV or RDD, there’s not much that can be done to save it. But there’s a groundbreaking development that’s allowing for the production of healthy roses from infected ones – and that’s tissue culture therapy.
What is Tissue Culture Therapy in Roses?
Tissue culture is a technique used to either rapidly grow thousands of roses or produce a healthy rose from one that is already infected with a virus.
How is Tissue Culture Used to Eliminate Viruses in Roses?
In tissue culture therapy, the shoot tip – also known as the meristem – is removed from the rose’s growing point and produced into a brand new, virus-free rose. The meristem is the part of the rose responsible for growth and development. Since meristematic cells are not connected to the rose’s vascular system, there is no pathway for viruses in the rose to reach them. And due to its high metabolic function, viruses aren’t able to multiply within the meristem.
The Tissue Culture Process
1. Mother Plant Selection - A “mother plant” from which the meristem will be removed is identified. It’s best to choose one that is healthy or minimally-infected. Because of the disconnect between the meristem and the rose’s vascular system, it’s okay for the mother plant to be a little bit sick.
2. Shoot Tip Sterilization - During any tissue culture process, the plant is cleansed of fungi, bacteria, insects, and any other external contaminants. Internal contaminants, such as viruses, are also cleaned out. Every part of the rose that goes onto the tissue culture medium needs to be completely sterile.
3. Culturing - The layers of the shoot tip are slowly peeled back with a hypodermic needle to reveal the meristem. The shoot tip is placed into a sterile, nutrient-loaded medium under controlled conditions where it can propagate into a new, healthy plant.
Benefits of Tissue Culture in Roses
Tissue culture in roses provides a range of benefits:
- Mass Propagation Tissue culture allows for the production of roses in large numbers in a short period of time.
- Healthy Roses The sterile conditions under which tissue culture is performed greatly reduces the risk of disease spread and pests.
- Genetic Uniformity The new roses cultivated will be identical to the selected mother plant – guaranteeing consistent traits.
- Year-Round Propagation Tissue culture allows healthy roses to be cultivated throughout the year, no matter the season.
Challenges
As effective as it may be, the tissue culture process presents a few challenges. It requires specialized equipment and highly-sterile environments, making it a less viable option for home gardeners.
Even with the fancy equipment, the process isn’t easy. It requires a great deal of precision. The meristem is tiny. Measuring less than 0.5 mm, it can barely be seen with the naked eye. That’s why a microscope is needed to perform the procedure.
It’s true that the smaller the meristem, the more likely it is to eliminate the virus. On the other hand, the smallest meristems are also the most difficult to generate new roses from.
Virus Testing & Detection in Roses
A rose may seem like it’s doing just fine, but viruses can be sneaky. Infected roses can often present as asymptomatic. To help navigate this challenge, scientists have developed testing techniques that allow for detection of viruses in roses – even in the absence of any symptoms.
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Enzyme-linked immunosorbent assay (ELISA) - a serological laboratory test that uses an enzyme to confirm the presence of an antigen or antibody in a sample.
Pros: ELISA is a sensitive test that provides rapid results. It is useful for handling large numbers of samples.
Limitations: ELISA can only detect viruses associated with known antibodies. -
Quantitative Polymerase Chain Reaction (qPCR) - a laboratory test that utilizes genomic information about the plant virus and selectively amplifies a small part of it.
Pros: qPCR is highly sensitive and can detect viruses at very low levels.
Limitations: qPCR can only detect specific viruses. -
High-Throughput Sequencing (HTS) - An advanced method for detecting and identifying plant viruses.
Pros: With its comprehensive capabilities, HTS can detect all viruses in a single assay, including novel variants. It does not require prior sequence information of an antibody.
Limitations: HTS can be expensive.
Tissue culture therapy has a long history of success in virus elimination in all types of plants and crops. And with advancements in technology and science, the future of healthy rose propagation is looking bright.
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