Phylogenetic Analysis of Grapevine Fanleaf Virus, Grapevine Virus A, and Grapevine Leafroll-Associated Virus 3 in Kazakhstan

Grapevine viruses reduce harvests and degrade fruit quality, but their genetic diversity in Kazakhstan has remained unexplored. We collected symptomatic leaves from local vineyards and recovered eleven fragments of the coat-protein gene: one from grapevine fanleaf virus, five from grapevine virus A, and five from grapevine leafroll-associated virus 3. After Sanger sequencing, we compared these fragments with more than one thousand international counterparts to place the Kazakh strains on the global family tree. The results reveal a clear spectrum of genetic diversity that mirrors each virus's route of spread. Grapevine virus A, which is moved both mechanically and by insects, proved the most variable; grapevine fanleaf virus, carried by dagger nematodes and pruning sap, had intermediate variability; and grapevine leafroll-associated virus 3, moved only by mealybugs and scales, was highly conserved. All Kazakh sequences fell inside established foreign lineages, showing that the viruses were imported multiple times rather than evolving locally. Grapevine virus A will require broad-coverage or multiplex PCR primers to avoid false negatives, whereas the stable leafroll virus can be monitored with a single high-sensitivity assay. Combined with vector management-mealybug control for leafroll, and nematode testing for fanleaf-these data lay the groundwork for a national clean-plant program and more resilient vineyards across Central Asia.