Concentration and specific infectivity changes of alfalfa mosaic virus during systemic infection

Alfalfa mosaic virus (AMV) concentration and specific infectivity were related to age of infection in tobacco; both decreased several fold between 1 to 5 weeks after inoculation. Even as virus concentrations increased, specific infectivity levels decreased. No differences, other than biological, were found between virus preparations with high and low specific infectivities. Logarithmic plots of specific infectivity decrease in vivo against time were linear when plants were grown in controlled environment rooms. Evidence was given to show that specific infectivity loss was not due to differential effects of plant age or purification. An extractable inactivating system may be implicated.