-6- 



1982) based on the inclusions they induce (Christie and 

 Edwardson, 1977; Edwardson and Christie, 1978; Hamilton et al . , 

 1981). This study explores the applicability of the light 

 microscope for diagnosing orchid viruses, as was done 

 previously for pepper viruses (Edwardson and Christie, 1979). 

 Electron microscopy of the inclusions found by light 

 microscopy was conducted to reveal the fine structure of the 

 inclusions . 



Materials and Methods 



Among the genera and viruses (in parentheses) studied in 

 this investigation were: Brassia ( uncharacterized bacilliform 

 virus), Cattleya (ORSV, CyMV), Cymbidium (ORSV, CyMV, 

 uncharacterized bacilliform virus), Masdevallia (bean yellow 

 mosaic virus), Phalaenopsis (ORSV, CyMV, cucumber mosaic 

 virus), and Vanil la (CyMV). For each plant tested, an unopened 

 new leaf and the first and second mature leaves (with or 

 without evidence of symptoms) were used. 



The Azure A and the calcomine orange/Luxol brilliant green 

 stain combinations ( 0/G ) were used (Christie and Edwardson, 

 1977; Hiebert et a_l . , 1984) for light microscopic examination 

 of viral inclusion bodies. The thick texture of most orchid 

 leaves precluded removal of epidermal strips for staining. To 

 overcome this problem, the following modifications were 

 employed: 1) For thin-leaved orchids (e.g., Phaius ) , leaf 



