STUDYING ERWINIA AMYLOVORA ISOLATES FROM SYRIA FOR COPPER RESISTANCE AND STREPTOMYCIN SENSITIVITY
A. Al-Daoude, M.I.E. Arabi , H. Ammouneh
A total of 75 Erwinia amylovora isolates, collected primarily from fire blighted quince (Cydonia oblonga) and pear (Pyrus syriaca and P. communis) shoots, were tested for copper resistance and streptomycin sensitivity. Sixty eight isolates, representing 90.6% of the total were inhibited by 10 µg/ml streptomycin and were thus regarded as streptomycin sensitive. On the contrary, three isolates that were not inhibited by 2000 µg/ml streptomycin were considered as resistant. Fifteen isolates grew well on casitone yeast extract medium in the presence of 1.2 mM copper sulfate and none survived
on the same medium containing 2.4 mM copper sulfate, indicating that most of the Syrian E. amylovora isolates are copper tolerant and could cause severe problems even in copper heavily sprayed orchards. The use of both bactericides in controlling fire blight disease in Syria is discussed.