Decline of specific infectivity of cowpea chlorotic mottle virus in vivo

Specific infectivity of cowpea chlorotic mottle virus (CCMV) declined with advancing age of infection in both whole plants and inoculated primary leaves. The decline began between 2 and 3 days after inoculation; 20–30 days later, purified preparations with similar amounts of virus nucleoprotein were only 1–5% as infective as the initial preparations. Specific infectivity was independent of host age, purification procedures, aggregation, and oxidative inhibitors. Specific infectivity increased when infected plants were transferred to 16°, presumably as a result of new particle formation; it declined rapidly at 33°.