BUDAGOVSKY 9 ROOTSTOCK: UNCOVERING A NOVEL RESISTANCE TO FIRE BLIGHT

Budagovsky 9 (B.9) apple rootstock, displayed a high level of susceptibility (similar to M.9 rootstock) to fire blight bacteria (Erwinia amylovora) when leaves of non-grafted B.9 plants were inoculated. However, when older B.9 rootstock tissue was inoculated directly with E. amylovora, rootstock tissue was resistant in both grafted and non-grafted plants. Comparisons of four scion cultivar ('Gala', 'Red Yorking', 'Jonagold' and 'Gingergold') and two sources of B.9 rootstock (Oregon, USA and Netherlands) showed no influence of scion cultivar or source of B.9 rootstock on symptom development. Further experiments investigating tissue age and its effect on resistance suggest B.9 asserts a form of persistent age related resistance in response to E. amylovora.