ABSTRACT
Several of the plant viruses are highly variable, but a few show only little variation. Alfalfa mosaic (AMV), cucumber mosaic (CMV), tobacco mosaic (TMV), tobacco ringspot, and turnip mosaic viruses belong to the former category, while cauliflower mosaic (CaMV), maize dwarf mosaic, and squash mosaic viruses belong to the latter category. TMV is the most highly variable virus.
