ISHS Acta Horticulturae 273: V International Workshop on Fireblight
ANTIBIOTICS PRODUCED BY STRAINS OF ERWINIA HERBICOLA THAT ARE HIGHLY EFFECTIVE IN SUPPRESSING FIRE BLIGHT |
| Authors: | R.S. Wodzinski, J.C. Clardy, S.J. Coval, S.V. Beer, C.H. Zumoff |
| Abstract:
Control of blossom infection caused by Erwinia amylovora is achieved commercially in many areas by spraying trees with streptomycin. Experimentally, when selected strains of Erwinia herbicola, a nonpathogenic bacterium, are applied to apple blossoms, disease control is comparable to that achievable with streptomycin. This investigation attempted to determine the importance of antibiotic production to the ability of E. herbicola to inhibit E. amylovora strain Ea273. The ability of 12 strains of E. herbicola to produce antibiotics inhibitory to Ea273 was determined with an in vitro plate assay. The five strains that showed significant antibiotic production were all rated as excellent antagonists of Ea273 in tests done in planta. However, the seven strains that did not produce antibiotics were rated only as good or moderate antagonists of Ea273. Although antibiotic production clearly is not the only mechanism by which E. herbicola inhibits Ea273, the ability to produce antibiotics may distinguish excellent and good antagonists of E. amylovora. Erwinia herbicola strains Eh318, Eh314 and Eh252, which produce antibiotics that are inhibitory to Ea273, are excellent antagonists of Ea273 in planta. The antibiotic of Eh318 was not inhibitory to Ea273 in the presence of arginine and histidine, and the antibiotic of Eh252 was not inhibitory in the presence of histidine. The toxicity of the Eh314 antibiotic to Ea273 was reduced in the presence of valine, leucine or lysine. These results indicate that Eh318, Eh314 and Eh252 produce three distinct antibiotics. A crude preparation of the Eh318 antibiotic delayed the development of disease in immature pear fruits induced by Ea273 but not by strain Ea273R318, which is resistant in vitro to the Eh318 antibiotic. Thus, the Eh318 antibiotic is effective in planta. Cells of Eh318 protected immature pears more effectively from infection by Ea273 than from infection by Ea273R318 (resistant to the Eh318 antibiotic). These results indicate that the Eh318 antibiotic is produced in planta and contributes to suppression of the disease. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
