Synchronization of Cowpea Chlorotic Mottle Virus Replication in Cowpea Leaves

Abstract

A technique that systemically inoculates cowpea [Vigna sinensis] leaves with cowpea chlorotic mottle virus (CCMV) is described. The upper leaves of cowpea plants are maintained at 10.degree. C and allowed to become infected with inoculum from lower leaves maintained at 32.degree. C; when the whole plant is shifted to 25.degree. C, synchronous virus replication starts in the upper leaves. Following the shift to 25.degree. C, no infectivity could be detected during the first 6 h, after which the infectivity increased exponentially between 8-20 h and linearly between 20-72 h. The time-courses of effectiveness of different inhibitors occurred sequentially and at different times during the infection. An actinomycin-D-sensitive step occurred at 10.degree. C, prior to the shift to 25.degree. C. A 2.0 mM guanidine-sensitive step occurred between 4-20 h and a cycloheximide-sensitive step occurred between 12-48 h after the shift to 25.degree. C. When the upper leaves were maintained at 5.degree. C while the infected lower leaves were at 32.degree. C, viral inoculum did not move into them, but rapid systemic infection occurred during the first 6 h after a shift of the whole plant to 25.degree. C.