-57- 

 advantages of light microscopy is the short time required 

 for tissue preparation and the extensive areas that can be 

 scanned. Also, many viruses induce characteristic 

 inclusions which can readily be recognized by this method 

 on the basis of morphology, staining reaction, and 

 location. However, the low resolution of light microscopy 

 is a major limiting factor in the interpretations of the 

 inclusions seen by this method. The 0/G and toluidine 

 blue methods described in this study provide the solution 

 to this problem, since the same (0/G) or adjacent 

 (toluidine blue) sections can be examined by both light 

 and electron microscopy. The 0/G was less satisfactory 

 for this purpose, since the fine structures of cells and 

 inclusions were adversely affected by its staining process. 

 Therefore, the toluidine blue method was used in this 

 study to reveal the fine structure of inclusions. In this 

 study, orchid infections caused by ORSV, CyMV, CMV, BYMV 

 and the Brassia rhabdovirus were readily studied by this 

 approach. Toluidine blue is not a selective dye, 

 however, it facilitates locating the inclusion-containing 

 areas for ultrathin sectioning. 



Fluorescent antibodies have been used extensively in 

 studying animal virus infections. However, their use in 

 the study of plant viruses has been very limited. This is 

 partly because the removal of non-specific staining of 

 plant tissues by fluorescent conjugates is very difficult, 



