In the apple blister bark syndrome, physiological stresses,adverse agronomic or climatic conditions, biotic agents can all be considered as predisposing factors potentially involved on the occurrence of the symptoms (Prodorutti et al., 2012). Previous studies conducted on host–pathogen interactions have recognised a plant-vigour mediated aetiology, stressing the physiological status as a discriminant on plant vulnerability (Kogel et al., 2006; Bostocket al., 2014).