-56- 



Discussion 



Negative staining using PTA has been used extensively 

 to detect plant viruses (Hitchborn and Hills, 1965; Doi et 

 al . , 1969). However, large grid areas need to be scanned 

 (time-consuming) in checking for the presence of virus 

 particles. VaMo negative staining provides a much more 

 efficient way to detect the infections of CyMV and ORSV 

 and other viruses (Boothroyd and Israel, 1980). Using 

 this method, as little as 6 minutes from grid preparation 

 to examination may be all that is necessary for a 

 diagnosis. The resolution and contrast of the VaMo stain 

 compare favorably with those noted for PTA. 



Processing tissues for electron microscopy is 

 extremely labor-intensive. Since virus-induced inclusions 

 are sometimes widely scattered in host tissues, success in 

 locating them by this conventional technique is often 

 limited. The procedure of thin sectioning described here 

 permits electron microscopy of materials selected by light 

 microscopy. For example, Russo et al_. (1982) failed to 

 find crystalline inclusions in broad bean true mosaic 

 infected tissues by using electron microscopic methods 

 exclusively. However, and contrary to their conclusions, 

 such inclusions were later found when light microscopic 

 methods were employed ( Ko , unpublished). One of the chief 



