Tobacco yellow vein,a virus dependent on assistor viruses for its transmission by aphids*

Tobacco yellow vein, a disease found in Malawi, is caused by a combination of two viruses transmitted in the persistent manner by aphids. One component, tobacco yellow vein virus (TYVV) is manually transmissible, but aphids transmit it only from plants also containing the other (assistor) component, which is not manually transmissible. Aphids also transmit TYVV from plants containing either of two other assistor viruses - tobacco vein-distorting and groundnut rosette assistor. A virulent isolate of TYVV infected Soja max, Arachis hypogaea and several solanaceous species. It infected plants already containing tobacco mottle or groundnut rosette viruses but not those containing a mild isolate of TYVV.