Rahnella aquatilis Ra39 - a bacterial antagonist against fire blight (Erwinia amylovora)

摘要

The epiphytic bacterial strain Rahnella aquatilis Ra39 was shown to reduce fire blight symptoms in fieldtrials during 1998, 1999 and 2000. The isolate was investigated on its mode of action against Erwiniaamylovora, the causal agent of the disease. The interaction between the populations of the fire blightpathogen E. amylovora strain Ea7/74 and R. aquatilis Ra39 was studied in vitro. In experiments with cocultures, a direct inhibition of Ea 7/74 by Ra39 in vitro was observed at a sucrose concentration of 0.2%but not at a concentration of 2%. Therefore competition for sucrose might be involved in the mode ofaction of R. aquatilis Ra39 against fire blight. Furthermore it could be shown that the lipopolysaccharideof R. aquatilis Ra39 is able to inhibit the multiplication of Xanthomonas campestris pv. begoniae, thecausal agent of the Oil Spot Disease of Begonia tuberhybrida in leaves of its host plant. From theobservations on this model system it was concluded that induced resistance may also play a role inantagonism of R. aquatilis Ra39 against E. amylovora.