A NEW FLOWER BREAKING TOBAMOVIRUS OF STREPTOCARPUS

A virus was isolated from Streptocarpus plants that showed colour brea king of the flowers. Initial diagnostic tests indicated that this viru s was a member of the Tobamovirus genus. The virus could be transmitte d mechanically to several test plants. Its stability in plant sap was in line with that of other tobamoviruses, i.e. infectivity was lost af ter 10 min incubation at 90 degrees C and after dilution to 10(-8). In addition, the morphology of the virus was typical for tobamoviruses. The particles had a length of about 304 nm. On test plants, the virus from Streptocarpus could be distinguished from 7 well-defined tobamovi ruses. Nicotiana glutinosa showed the most characteristic symptoms. In agar double-diffusion tests and/or double antibody sandwich enzyme-li nked immunosorbent assays, no cross reactivity was observed in heterol ogous combinations with these 7 and 3 other tobamoviruses. Mechanical inoculation of the virus to virus-free Streptocarpus plants resulted i n the appearance of flower breaking in about 50% of the plants. On the basis of these findings, it is concluded that the virus that causes f lower breaking in Streptocarpus is a distinct member of the Tobamoviru s genus, and the name Streptocarpus flower-break virus is proposed.