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Co- and super-infection exclusion of Beet necrotic yellow vein virus and Beet soil-borne mosaic virus

Mark Varrelmann: Inst of Sugar Beet Research

<div></p> <p><em>Beet necrotic yellow vein virus </em><span>(BNYVV) and <em>Beet soil-borne mosaic virus</em> (BSBMV) belong to the genus <em>Benyvirus</em>. Roots infected with BSBMV appear asymptomatic whereas light yellow vein banding, mottling and mosaic patterns can be observed on the foliar. In contrast, BNYVV induces a reduced root size with massive root proliferation and vein yellowing on the foliar. Since BNYVV and BSBMV share the same host-range and vector species; mixed infections occur frequently. Information on interaction between both viral species is limited. Therefore, the species interaction was studied in <em>Nicotiana</em> <em>benthamiana</em> and <em>Beta vulgaris</em> using fluorescently labelled cDNA full length clones. Viral populations of BYNVV and BSBMV remained spatially separated with only a few co-infected cells after simultaneous inoculation into <em>N.</em> <em>benthamiana</em>. Furthermore, plants that were initially infected with BNYVV could not be super-infected with BSBMV. Although both viral species showed a strong exclusion in mixed infections, reassortment experiments in <em>Beta vulgaris </em>demonstrated that viral RNAs of BNYVV can be replaced by BSBMV and <em>vice versa</em> resulting in a systemic infection with altered symptom development. Moreover, it was proven whether both viral species are able to form chimeric RNAs by recombination. The observation of spatial separation possess significant impact on plant virus evolution by acquisition of foreign sequences by means of recombination or reassortment.</span></div>