PROPERTIES OF CUCUMBER BULGARIAN LATENT VIRUS A NEW SPECIES IN THE GENUS TOMBUSVIRUS
D. Kostova, V. Lisa, L. Rubino, C. Marzachì, P. Roggero, M. Russo
This paper reports the properties of a tombusvirus isolated by mechanical inoculation from severely stunted and mottled cucumber plants, infected also by Watermelon mosaic virus (WMV), grown in glasshouses in the Plovdiv area (Bulgaria). After separation from WMV, this virus was characterized biologically (host range reaction), physicochemically, molecularly, and ultrastructurally. The virus invaded systemically with difficulty different cucumber cultivars, producing latent infections. It was not serologically related to 24 different viruses in the genera Tombusvirus, Carmovirus, Necrovirus and Sobemovirus, but it had physico-chemical and ultrastructural properties typical of tombusviruses. The genome, which was totally sequenced, is a single-stranded positive-sense RNA of 4576 nucleotides. The genome structure was identical to that of tombusviruses but the sequence homology of the protein cistrons was not higher than 41% when compared to that of all sequenced members of the genus Tombusvirus. Distinct differences were also found in the N-terminal region of the ORF 1 sequence. The cucumber virus was therefore identified as a new putative tombusvirus species provisionally named Cucumber Bulgarian latent virus (CBLV).