Characterization and developing effective screening methods of bacterial blight of highbush blueberry in the Lower Mainland of British Columbia

The Lower Mainland of BC is a major region for the cultivation of highbush blueberry in Canada. Bacterial blight caused by Pseudomonas syringae (Ps) is an endemic disease of highbush blueberry in BC and causes significant damage in young plants. The objectives of this study were: (i) to characterize isolates of Ps and assess their virulence; and (ii) to develop reliable screening methods for pathogenicity test and disease resistance. About 200 isolates of Ps were collected in 2019 from suspected bacterial blight-infected plant samples. Of these, 51 representative isolates were used for characterization and virulence diversity. Isolates were confirmed as Ps by growing them on the Ps-selective media
Tri-Society Virtual Conference 18
KBC (King’s B media with boric acid, cephalexin, and cycloheximide), and further characterized using the LOPAT test (levan, oxidase, pectolytic activity, arginine dihydrolase, and tobacco hypersensitivity reaction). Pathogenicity and virulence of these isolates were performed using blueberry leaf disc and detached leaf assays. About 61% of the tested isolates (n = 6) were confirmed as Ps and were pathogenic. Six pathogenic isolates were further evaluated by inoculating flower buds of two varieties ‘Chandler’ and ‘Duke’. All six isolates caused bacterial blight on flower buds of both varieties. In addition, six screening methods were compared by inoculating Ps in intact blueberry plants and three methods (wounding stem apex, removing leaf and wounding stem, and wounding leaf with carborundum) performed better than the remaining of screening methods.