By: Madalyn Shires and Kevin Ong
Fasciation, also known as cresting, is a rare phenomenon that occurs in more than 100 species of plants, including roses. It commonly afflicts tobacco, which makes it an economically important pathogen. This distortion, unusual and unpredictable, does no lasting harm to the plant. Some plants are highly prized and bred for their unique fasciated characteristics.
Fasciation symptoms include flattened stems and shoots that seem to be made of several fused shoots (Fig. 1) as well as flattened, elongated, or misshapen flower heads (Fig. 2). Such characteristics appear in the stems, leaves, flowers, and fruit of most plants.
The deformity is often localized to a single stem (Fig. 3). Pruning the infected area usually stops the abnormal growth and it rarely occurs again, unless it is in the plant’s genes. Though symptoms tend to occur only occasionally and in localized plant parts, some plants such as forsythia and Veronicastrum virginicum may repeatedly show fasciation year after year because of a genetic predisposition. Since abnormalities in actively growing tissues cause the deformities, symptoms are most prevalent during spring and summer.
Though caused by many factors, fasciation symptoms are usually triggered by an abnormal hormonal change in the apical meristem, or growing tip, of the plant. During active growth, the apical meristem typically concentrates around a single point to produce cylindrical tissue. But, during fasciation, the growing tip elongates perpendicularly to the direction of growth, creating flattened, distorted tissue.
Other causes may be a bacterial, viral, or fungal infection, random genetic mutation, frost damage, animals and insects, and chemical or mechanical injury from cultural practices. The phytopathogenic bacterium, Rhodococcus fascians, produces fasciated symptoms in a wide range of hosts. Fasciation can also appear in conjunction with Rose rosette virus, mainly because of the lowered defense system of the infected roses.
There are not many control measures associated with fasciation. Various factors cause the condition, it does no lasting harm to the plant, and is usually localized and temporary. Prevention entails avoiding injury to plant bases, avoiding overwatering, and not grafting fasciated plants. Always use good hygiene when pruning plants with fasciation symptoms. Though it is not contagious, the causal agents might be and can be controlled using respective measures (for example, fungicides for fungal agents). If symptoms are present, prune out affected plant parts and dispose of them properly by burning plant material or placing pruned material in with non-plant-material trash. Do not compost with it because if a pathogen caused the symptoms, it could infect other plants through compost application.
Fasciation. Royal Horticultural Society. https://www.rhs. org.uk/advice/profile?pid=525
Klingaman, Gerald. 2008. Plant of the Week: Fasciated Plants (Crested Plants). The University of Arkansas Division of Agriculture. https://www.uaex.edu/yardgarden/resource-library/plant-week/fasciated-2-22-08. aspx For more information, contact the Texas Plant Disease Diagnostic Lab at email@example.com or Kevin Ong at PlantDr@tamu.edu.
Katherine Olive, Undergraduate Extension Assistant, contributed to the manuscript of this publication.
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