AbstractOut of 12 populations of X. diversicaudatum tested, 8 were efficient vectors of arabis mosaic virus type-British strain (AMV-T). A population from USA transmitted the virus at a rate intermediate between these 8 efficient populations and one from Spain which transmitted AMV-T infrequently. Spanish nematodes did not transmit a 2nd strain of virus (AMV-W) and French and Italian nematodes only infrequently transmitted AMV-W. However, AMV-W was relatively frequently transmitted by 9 other populations of X. diversicaudatum. Petunia hybrida and Chenopodium quinoa virus-source and bait plants were used with AMV-T and AMV-W respectively and AMV-T was transmitted by substantially more of the nematodes from 8 of the populations than was AMV-W. In a separate test AMV-T was more frequently transmitted when P. hybrida rather than C. quinoa were used. Differences in transmission between the 2 strains of AMV were much larger than the differences when the 2 plant species were compared. It is suggested that the differences may be inherent in the specificity of the relationships between AMV-T and AMV-W and X. diversicaudatum.