CHARACTERIZATION OF ERWINIA AMYLOVORA STRAINS FROM DIFFERENT HOSTS AND GEOGRAPHICAL AREAS

Fire blight is one of the most important diseases from a quarantine standpoint as several important pome-fruit producing regions are still free of the pathogen, Erwinia amylovora (van der Zwet and Beer, 1995). It apparently originated in North America based on the fact that, until the turn of the century, there were no reports of the disease outside the continent.
Generally, E. amylovora causes the disease on pears and apples.
Strains isolated from Rubus plants, however, infect only Rubus plants and not apples and pears (Starr et al., 1951). Based on RFLP analysis of the E. amylovora hrp gene cluster, Laby and Beer (1992) suggested that two distinct groups of Rubus-specific strains may exist. “Bacterial Shoot Blight of Pear” pathogens were isolated from Asian pears in Hokkaido, Japan, and were identified as strains of E. amylovora (Tanii, 1981; Beer et al., 1996). Given the possible diversity of strains within the species, we decided to investigate the microbiological and molecular biological characteristics of strains of E. amylovora.

Eighty-four strains of E. amylovora isolated from diverse hosts and geographical areas were collected: sixty-six strains from pomaceous plants from many locations including North America, Europe, the Middle East and New Zealand; ten strains from Rubus in North America; and eight strains from Asian pears on Hokkaido, Japan.
The metabolic capabilities of all the strains for 95 different carbon sources were examined by the BiOLOG^TM system.
Most E. amylovora strains oxidized N-acetyl-D-glucosamine, L-arabinose, D-fructose, D-galactose, -D-glucose, meso-inositol, D-mannitol, -methyl-D glucoside, D-psicose, D-sorbitol, sucrose, D-trehalose, methyl pyruvate, monomethylsuccinate, D-gluconic acid, succinic acid, bromosuccinic acid, L-alanine, L-glutamic acid, glycyl-L-glutamic acid, glycerol, glucose 1-phosphate, and glucose 6-phosphate under the test conditions used.

The carbon source utilization profiles of each strain were compared by a cluster analysis.
Most strains isolated from pomaceous hosts clustered together.
Supporting a previous observation (Laby and Beer, 1992), at least two different groups were recognizable for strains pathogenic on Rubus spp.
One group, designated “Rubus I”, showed “metabolic fingerprints” much more similar to pomaceous strains compared to the other group, “Rubus II”. The four “Rubus II” strains tested and one “Rubus I” strain metabolized cis-aconitic acid and citric acid.
Strains isolated on Hokkaido formed two

VII International Workshop on Fire Blight

J.-H. Kim, S.V. Beer, A. Tanii, C.H. Zumoff, R.J. Laby, H.L. Gustafson, H.S. Aldwinckle

https://doi.org/10.17660/ActaHortic.1996.411.37