Genetic analysis of Grapevine leafroll‐associated virus 3 population from Galicia, Spain

Grapevine leafroll‐associated virus 3 ( GLR aV‐3; Ampelovirus , Closteroviridae ) isolates from Galicia in northwestern Spain were selected to characterize their genetic diversity according to different factors (age, origin, location, variety, etc.). The vines belonged either to local white and red varieties autochthonous to Galicia or to varieties from other Spanish regions but widely used in Galicia. These GLR aV‐3 isolates came from different vineyards in Galicia located in coastal or inner areas. Multiplex RT ‐ PCR allowed the detection of isolates belonging to groups I, II, III–V and VI. Two genomic regions were studied in the isolates, the HSP 70h and the capsid protein, using specific primers that allow the detection of variants from groups I to V. Some possible recombinants could be detected; however, multiple infections with different variants indicated that they were not genuine recombinants. No differences were found in the population structure considering variety or geographical factors. Isolates belonging to four groups were found in the distinct areas surveyed: groups I and II were the most common, followed by groups VI and III , as is the case in the rest of the world. In the same surveys, the presence of insect vectors for GLR aV‐3 was investigated and found lacking in inland areas but present in those with milder climate. Genetic analysis did not support isolation of the GLR aV‐3 isolates in Galicia, suggesting that the uncontrolled exchange of infected vines and/or rootstocks has been a major agent of virus spread.