A single U/C nucleotide substitution changing alanine to valine in the beet necrotic yellow vein virus P25 protein promotes increased virus accumulation in roots of machanically inoculated, partially resistant sugar beet seedlings
Autor/in:Koenig, R., S. Loss, J. Specht, M. Varrelmann, P. Lüddecke, G. Deml
Beet necrotic yellow vein virus (BNYVV) A type isolates E12 and S8, originating from areas where resistance-breaking had or had not been observed, respectively, served as starting material for studying the influence of sequence variations in BNYVV RNA 3 on virus accumulation in partially resistant sugar beet varieties. Sub-isolates containing only RNAs 1 and 2 were obtained by serial local lesion passages; biologically active cDNA clones were prepared for RNAs 3 which differed in their coding sequences for P25 amino acids 67, 68 and 129. Sugar beet seedlings were mechanically inoculated with RNA 1+2/RNA 3 pseudorecombinants. The origin of RNAs 1+2 had little influence on virus accumulation in rootlets. E12 RNA 3 coding for V67C68Y129 P25, however, enabled a much higher virus accumulation than S8 RNA 3 coding for A67H68H129 P25. Mutants revealed that this was due only to the V67 ‘GUU’ codon as opposed to the A67 ‘GCU’ codon.