CHAPTER 1 

 INTRODUCTION 



Orchidaceae is one of the largest and most diverse 

 families of plants. It includes 7-10% of all flowering plant 

 species (Dressier, 1981). Orchids are widely grown throughout 

 the world for sale as cut flowers or as potted plants. The 

 value of an individual mature plant can range from a few 

 dollars to several thousand dollars. In Florida, orchid 

 production has been estimated to have an annual sale value of 

 three million dollars (Anonymous, 1983), while the Federal 

 Republic of Germany imported $22.9 million of fresh-cut orchids 

 (Anonymous, 1978). 



The value of individual orchids is reduced considerably by 

 plant pathogenic infections. Viruses are particularly 

 problematic in orchids wherever they are grown. The most 

 serious damage occurs when symptoms become evident on the 

 flowers. Twenty-two viruses have been reported in orchids 

 (Lawson and Horst, 1984). Cymbidium mosaic ( CyMV ) and 

 Odontoglossum ringspot (ORSV) viruses, the first orchid viruses 

 to be described, are the most prevalent. Many of the other 

 viruses of orchids have only recently been described and have 

 not been well-characterized. The prevalence of viruses in 



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