-74- 



*For light microscopy, Azure A and 0/G stains were used (see 

 chapter 2). For electron microscopy, 2% potassium 

 phosphotungstate ( pH 6.9, containing 0.025% bacitracin) 

 was used for negative stain. For serology, the SDS immuno- 

 diffusion test as described by Wisler et a_l. (1982) was 

 used. The CMV, ORSV, and CyMV antisera were as described 

 in chapter 3 . The BYMV capsid and nuclear inclusion 

 antisera used were obtained from C.-A. Chang. 



**NE: Non-evident symptom. 



