Intracellular occurrence of cowpea mild mottle virus in two unrelated plant species.

The filamentous particles of cowpea mild mottle virus (CMMV) were detected only in the cytoplasm of palisade, mesophyll, parenchyma and epidermal cells of Glycine max (Papilionaceae) and Nicotiana clevelandii (Solanaceae). They were aggregated to form either sheets or bundles or, more frequently, brush-like inclusions. Although CMMV was initially considered to be a possible member of the Carlavirus group, it differs from aphid-borne carlaviruses in its intracellular occurrence and transmission by whiteflies and in being frequently seed-transmitted in some leguminous hosts. Because CMMV is also serologically unrelated to any of 12 recognized carlaviruses, we suggest that it now be removed from the carlavirus group and left unclassified until the taxonomic significance of these differences has been fully evaluated.