The objective of the proposed work is to uncover mechanisms by which organisms can be immune to infection by a specific virus. This system consists of lines of cowpeas (the "Blackeye pea," Vigna unguiculata) and two strains of cowpea mosaic virus, SB and DG. Several lines are immune to SB, but protoplasts from primary leaves of those same lines were susceptible. Some postulated explaations for this situations will be tested. One cowpea line, "Arlington," was not only immune to SB as seedlings but was a source of highly resistant protoplasts. The virus strain DG infected seedlings and protoplasts of all the lines tested. Analyses for virus replication intermediates were developed. These will be applied to protoplasts from Arlington and from the other lines inoculated with SB or DG. The objective is to identify a site at which SB replication in Arlingtn protoplasts is restricted.