Studies 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 for their biocontrol effect against fire blight (Erwinia amylovora) and for resistance induction activity. The experiments were carried out under controlled climatic conditions in a greenhouse. M26 apple rootstock was used as host plant. Furtheremore, enzyme activities of ß-glucosidase and PR-protein (chitinase) were estimated as markers of resistance in physiological studies,. 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 ß-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 apple rootstock.