Phylogenetic Analysis of Allorhizobium vitis Strains in the Okanagan Valley, British Columbia, Canada

ABSTRACT Grapevine crown gall (GCG), characterised by the formation of galls and root necrosis, is an economically devastating disease that affects grapevines worldwide. The primary causal agent of GCG is the bacterium Allorhizobium vitis , which is spread primarily through infected grapevine planting material. The Okanagan Valley of British Columbia, Canada, one of the country's premier cold‐climate wine‐producing regions, is plagued by GCG. However, little is known about the epidemiology and genetic diversity of Okanagan A. vitis strains. We sequenced the genomes of 14 putative virulent ( virD2‐ positive) and 4 tumorigenic A. vitis strains collected from the Okanagan Valley and performed a phylogenomic analysis in the context of all previously sequenced virulent strains from around the globe. We found that the Okanagan strains fell into four distinct clades. Okanagan Valley A. vitis strains were grouped alongside strains isolated from Australia, Europe and the United States. One clade contained only strains isolated from the Okanagan Valley. All strains carrying Ti plasmids with characterised opine‐types in these clades, including the Okanagan strains isolated in this study, carried octopine/cucumopine (O/C)‐type (Type IV.b) plasmids. Single‐nucleotide polymorphism (SNP) analysis of Okanagan A. vitis strains found that there was no clear relationship between genetic similarity (few SNP differences) and cultivar, rootstock or nursery origin of the plant material the strains were isolated from. Results of this study enhanced our understanding of A. vitis diversity in the Okanagan Valley and supports previous work outlining the need for strict phytosanitary control measures in grapevine nurseries.