Occurrence of phytoplasmas in leafhoppers and cultivated grapevines in Canada

Following the recent detection of bois noir, X-disease and aster yellow (AY) in Canadian vineyards, a survey was conducted in 2006-2008 in vineyards located in Ontario (ON), British Columbia (BC) and Quebec (QC). PCR tests were used to detect phytoplasmas in grapevine cultivars and leafhopper species, and identify phytoplasma strains. The overall detection of phytoplasmas was <1% in BC, and ranged from 2.4% to 8.3% in ON and QC, respectively, with significant variability between years, cultivars and locations. A large proportion of phytoplasma-infected grapevines were symptomless and the cultivars merlot and pinot gris were the only two cultivars in which no phytoplasma were detected. Aster yellow phytoplasma strains belonging to the subgroups 16SrI-A, -B, and -C were detected in grapevines, with 16SrI-A being the most frequently found. Phytoplasma DNA was detected in 37 leafhopper species, out of which 11 are known vectors. Most leafhopper species in which phytoplasma DNA were detected are grass feeders, with the AY vector Macrosteles quadrilineatus constituting a strong potential candidate for AY transmission in ON and QC vineyards. Five new sequences of phytoplasma were found in grapevines, and 11 in leafhoppers: they were registered in GenBank. The possibility of phytoplasma transmission between leafhoppers and grapevines is discussed.