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Title: Viruses that enhance the aethetics of some ornamental plants: beauty or beast?

item VALVERDE, RODRIGO - Louisana State University
item SABANADZOVIC, SEAD - Mississippi State University
item Hammond, John

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2012
Publication Date: 3/13/2012
Citation: Valverde, R.A., Sabanadzovic, S., Hammond, J. 2012. Viruses that enhance the aethetics of some ornamental plants: beauty or beast?. Plant Disease. 96(5):600-611.

Interpretive Summary: Plant virus infections are typically considered detrimental, causing losses to both productivity and quality. This is usually true for ornamental plants as well as for agronomic crops. However, there are a limited number of examples in which virus infection confers desirable aesthetic qualities on ornamental hosts. Plants with unusual foliage and flowers are often highly prized by horticulturalists and ornamental plant enthusiasts, and selections of many ornamental plants with variegated leaves of unusual floral patterning have been propagated and commercialized as distinct cultivars. Although some of these patterns are under genetic control, in other instances they are caused by virus infection. Examples of virus infection resulting in desirable appearance of ornamental plants are discussed, including the potential hazards that may result from transmission of virus to other ornamental or agronomic crops, with the possibility of economic loss. Increased testing of ornamental plants prior to importation and distribution is recommended, in order to prevent introduction of new viruses that may cause significant crop losses. This information will be of interest to importers and producers of ornamental crops, and to the regulatory authorities responsible for crop inspection and plant quarantine.

Technical Abstract: Although most viruses that infect plants cause diseases that are detrimental to the plant, there are some instances in which infections by mild viral strains of a virus have been used to protect the plant against severe strains of the same virus. There are other viruses that can cause desirable effects in plants, and infected plants have been selected or in some cases used, by ornamental horticulturists to enhance the aesthetics of the plants. In most cases, this translates into an increase in their commercial value. There are several examples of ornamental plants being more marketable when infected by a particular virus than virus-free. Plants with unusual foliage or/and flowers are highly sought by horticulturists and many ornamental plant enthusiasts. Selections of many ornamental plants exhibiting green leaves with other colors such as white, yellow or red, alone or combined (generally known as variegations) have been propagated and commercialized as distinct cultivars. Similarly, this practice has been conducted also with flowers exhibiting desirable aesthetic value usually in the form of flower breaking. Flower breaking describes the appearance of the flowers in which the petals, instead of being uniformly colored, are variegated due to the irregular distribution of anthocyanin. Leaves can also exhibit vein discolorations that range from white to yellow. Most foliar or flower variegations and vein discolorations are the product of mutations that affect plastid development or transposable genetic elements that result in anomalous production of pigments. Plant viruses can cause symptoms that mimic genetic variegations and vein discolorations. Differentiation between genetic variegations and variegations caused by plant viruses is not an easy task and it is often assumed that variegations are of genetic nature. This illustrates, at least from the commercial point of view, the desirable effect of certain viral infections. In recent years, there have been reports of plant viruses associated with unique phenotypes of ornamental plants, and some of them are being marketed as novel plant cultivars. Here we discuss some viruses that enhance natural beauty of certain ornamentals and increase their commercial value, and discuss potential drawbacks and repercussions associated with their use.