Molecular characterization of divergent isolates of grapevine red blotch virus from Blanc du Soleil, an interspecific hybrid white grapevine cultivar

During routine virus screening, grapevine red blotch virus (GRBV; genus Grablovirus, family Geminiviridae) was detected in several samples of a recently released interspecific hybrid wine grapevine cultivar Blanc du Soleil (BdS, US PP 34,483 P2, 2022). Molecular characterization of the BdS GRBV isolates revealed the presence of distinct complete genomes in nine isolates, with atypical lengths of 3,181 to 3,183 nucleotides (nt) relative to the expected 3,205-3,208 nt reported for GRBV isolates characterized to date globally. The difference in length was mainly due to deletions in the long intergenic region of the BdS GRBV isolates. In a phylogenetic reconstruction, the variant BdS GRBV isolates formed a monophyletic subclade basal to the clade II isolates to whom they were more phylogenetic related than the clade I isolates. On average, complete genomes of these new isolates are 98.75% identical to each other, 96.66% identical to clade II isolates, and 92.02% identical to clade I isolates. Evolutionary analysis also revealed the occurrence of recombination in the history of these new isolates.