Investigations on induced resistance against fire blight (Erwinia amylovora) with different bioagents

Three different bioagents (BION, BioZell-2000B, an etheric oil from Thymbra spicata, and the antagonistic bacterium Rahnella aquatilis Ra39) were tested on their biocontrol effect against fire blight (Erwinia amylovora) and on resistance induction activity. The experiments were carried out under controlled climatic conditions in the greenhouse. For the studies M26 apple rootstock was used as host plant. Moreover as marker of resistance in physiological studies enzyme activities of beta-glucosidase and PR-protein (chitinase) were estimated. The treatment with BION, BioZell-2000B and Ra39, resulted in a marked reduction of the disease index up to 64%. This was correlated with a decreasing effect on the growth of bacteria up to 64% during the course of infection. In the physiological studies significant changes in the activities of beta-glucosidase and chitinase were found after treatment of all three bioagents. Thus the biocontrol effect was correlated with a resistance induction in the host plant of the apple rootstock M26.