ISHS Acta Horticulturae 590: IX International Workshop on Fire Blight
BIOLOGICAL CONTROL OF FIRE BLIGHT BY USING RAHNELLA AQUATILIS RA39 AND PSEUDOMONAS SPEC. R1 |
| Authors: | P. Laux, O. Baysal, W. Zeller |
| Keywords: | Erwinia amylovora, Rahnella aquatilis, Pseudomonas, antagonism, mode of action, induced resistance |
| Abstract:
The bacterial strains Rahnella aquatilis Ra39 and Pseudomonas spec. R1 were investigated for their mode of action against Erwinia amylovora (strain Ea7/74). Pseudomonas spec. R1 expressed antibiosis against Ea7/74 independent from the amino acid composition of the medium. In contrast Ra39 did not show an antibiotic effect. The influence of the antagonistic strains on the population of the pathogen was further studied in co-cultures using different media. An inhibitory effect of both antagonists on Ea 7/74 could be seen only at the beginning of the third day after inoculation. The inhibitory effect of strain Ra39 was shown to depend on the sucrose concentration of the medium; while inhibition could be observed at a concentration of 0.2%, there was no effect at a sucrose concentration of 2%. Therefore, competition for sucrose was suggested as one mechanism of the strain Ra39 against Ea7/74. The inhibitory effect of strain R1 to Ea7/74 in co-culture was independent from the sucrose concentration and is probably based on antibiosis. Additionally, the induction of the superoxide radical by lipopolysaccharides (LPS) was studied as an indicator for an induction of resistance. The LPS of Ra39 was shown to cause the formation of superoxide in leaves of apple, bush bean and begonia. This effect was not observed with LPS of R1. Therefore, induced resistance might be a non-specific mechanism of Ra39, which is affecting also other bacterial plant pathogens beside E. amylovora. | |
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