QUARANTINE VIRUSES, VIROIDS AND PHYTOPLASMAS THAT AFFECT MOVEMENT OF ORNAMENTAL PLANTS
Some viruses, viroids and phytoplasmas infecting ornamental crops have been widely distributed around the world and have caused significant damage and economic losses. When trade in ornamentals was initiated many years ago, the threat of distributing viruses and viruslike agents was minimized because much of the germplasm was exchanged as seed. In the last fifty years the transport of vegetatively propagated clonal material has resulted in the dissemination of many viral and other graft-transmissible agents. Some of the first viruses transported across national and international borders were those infecting cut flower crops. Infected cuttings of carnations and chrysanthemums carried disease agents over long distances. More recently, vegetative propagation of Petunia and perennial crops such as Hosta and seedlings of Eustoma served as virus carriers. In some instances the agents were spread before it was recognized the material was diseased. In other instances, methods of detection and diagnosis for a specific disease agent were not developed for certification purposes. Quarantine regulations are designed primarily to exclude the movement of pathogens into geographic areas where they were not previously known to occur. Regulations have also been developed to restrict the movement of disease agents into areas where they may occur but distribution is limited. Practical procedures of certification depend on adequate methods of detection. Certification also ensures that standards of quality are maintained for optimum productivity of each of the major crops in international commerce. The purpose of this review is to examine the differences in quarantine regulations between the European Union and the U.S. and how the application of these regulations affects the movement of plant material. Virus and viruslike agents of quarantine importance are presented. In addition, the potential of some"new" viruses, viroids and phytoplasmas to limit distribution of ornamentals are discussed.
Lawson, R.H. and Hsu, H.T. (2006). QUARANTINE VIRUSES, VIROIDS AND PHYTOPLASMAS THAT AFFECT MOVEMENT OF ORNAMENTAL PLANTS. Acta Hortic. 722, 17-30
quarantine regulations, quarantine pathogens, certification standards