Involvement of the cucumber necrosis virus coat protein in the specificity of fungus transmission by Olpidium bornovanus.

Cucumber necrosis (CNV) and the cherry strain of tomato bushy stunt (TBSV-Ch) are tombusviruses which differ in transmissibility by the fungus Olpidium bornovanus (Sahtiyanci) Karling (= O. radicale Schwartz and Cook). Zoospores acquire and transmit CNV, but not TBSV-Ch, in the in vitro manner. To assess the role of the coat protein in the specificity of fungus transmission, reciprocal exchanges were made between the coat protein genes of these two viruses in full-length infectious cDNA clones. Virions containing a modified TBSV-Ch genome with the CNV coat protein gene were efficiently transmitted, but those containing a modified CNV genome with the TBSV-Ch coat protein gene were not. This is the first direct demonstration for the role of a viral coat protein in the specificity of transmission by a fungus.