Abstract
Differences in symptom expression and growth curve exist between two California strains, B and C of tobacco rattle virus, each of which possesses 3 components of different particle lengths and is serologically related to two English strains. With increasing age of infection from 3 to 35 days, the particle populations of strains B and C show a shift in the middle to bottom component ratio from about 2 to 0·9. An unstable 1600 to 1700 Å fraction recovered during periods of most rapid synthesis of the strain C may be implicated in the appearance of normally present 800 to 900 Å rods.