PLANT EXTRACTS WITH A RESISTANCE INDUCTION EFFECT AGAINST FIRE BLIGHT (ERWINIA AMYLOVORA)

After first results, in which different plant extracts (PE) showed beside protective characters a resistance induction effect against Fire Blight (Erwinia amylovora), further four from Reynoutria sachalinensis, Hedera helix, Viscum album and Alchemilla vulgaris were studied on their effect on pathogenesis and physiological changes in the host plant Cotoneaster watereri. Experiments were undertaken with seperated leaves of the testplant under controlled cultural and experimental conditions (climatic chamber).

All four PE led to marked increase of resistance in the test plant compared to the control. Moreover the number of bacteria per leaf were reduced in the course of pathogenesis. Physiological studies gave an indication for an increase in the phenol metabolism of the host plant after treatment with the inducer, as for instance an enhancement of the total phenol content with increased enzymatic activities of -glucosidase, phenylalanine-ammonia-lyase (PAL), peroxidase (PO) and phenoloxidase (PPO).