Beet black scorch virus in Iran is more diverse than anywhere

Merhvar, Mohsen Bragard, Claude [UCL]

The diversity of iranian Beet black scorch virus and its satellite was studied by sequence analysis of selected samples. The presence of the BBSV was systematically associated with the presence of the Beet necrotic yellow vein virus, the Beet soil-borne virus or the Beet virus Q. The complete genome sequences of seven Iranian BBSV were determined : three BBSV associated with a satellite and four BBSV without. They showed identities ranging from 99% to 88% nucleotide identities. Amino acid identity in the predicted genes ranged from 59% in the p10 gene only evidenced in the BBSV-CO US isolate to 100% in the p7a gene of the ‘Ningxia’ isolate from China. The level of diversity at nucleotide level is higher in Iran than observed for the previously reported BBSV from China, U.S.A. or Europe, raising the hypothesis of multiple contaminations of the sugar beet in Iran, possibly from a Brassicaceae. Such diversity, including additional putative genes, will be discussed. The Iranian BBSV satellite comprises 617 nucleotides rather than 615 for BBSV-X satellite from China, with an identity of 86% between both sequences. By mechanical infection, the virus gave a localized infection on Chenopodium quinoa and Beta macrocarpa. The 3′ UTR of some sources of BBSV showed significant changes at nucleotide level, but with no structural changes in the secondary structure of this region of major importance for the viral replication.