אסיף מאגר המחקר החקלאי

Streptomycin resistance of erwinia amylovora in israel and occurrence of fire blight in pear orchards in the autumn

Year:

1999

Source of publication :

Authors :

Volume :

489

Co-Authors:

Manulis, S., Dept. of Plant Pathology ARO, Volcani Center, Bet-Dagan 50250, Israel
Zutra, D., Dept. of Plant Pathology ARO, Volcani Center, Bet-Dagan 50250, Israel
Kleitman, F., Dept. of Plant Pathology ARO, Volcani Center, Bet-Dagan 50250, Israel
Dror, O., Dept. of Plant Pathology ARO, Volcani Center, Bet-Dagan 50250, Israel
Shabi, E., Dept. of Plant Pathology ARO, Volcani Center, Bet-Dagan 50250, Israel
David, I., Dept. of Fruit Trees ARO, Volcani Center, Bet-Dagan 50250, Israel
Zilberstaine, M., Dept. of Crop Protection Extension Service, Tel-Aviv 61070, Israel

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Abstract:

Due to failure in control of fire blight with streptomycin, the distribution of streptomycinresistant strains of Erwinia amylovora was surveyed in Israel. During 1994-1998 163 pear, apple, loquat and quince orchards were monitored. Streptomycin-resistant strains of Erwinia amylovora were recovered from flowers and from infected branches collected from 25 locations, in the Sharon, Galilee and Golan Heights regions. In the Sharon region, all the isolated strains of E. amylovora were streptomycin-resistant, whereas in the Galilee and the Golan Heights resistant as well as sensitive E. amylovora strains were recovered from different locations. In the southern coastal plain and in the northern Negev no resistance could be detected. In 9 locations, which were monitored during several years, only resistant strains were found, whereas, in 8 locations only sensitive strains were recovered. Streptomycin-resistant strains of E. amylovora did not hybridize with the DNA probe SMP3, and resistance could not be transferred by mating to a sensitive strain, suggesting that streptomycin resistance in Israel is not plasmid-mediated. Since 1997 streptomycin was withdrawn from the recommendations for fire blight control and instead oxolinic acid (Starner) has been recommended. Fire blight symptoms were observed, for the first time, on pear blossoms during the autumn of 1994. A high population of 2x106-6x107 CFU/flower in the autumns of 1995 and 1996 was correlated with the appearance of blossom blight symptoms. The presence of resistant strains during the autumn in pear and loquat orchards may form a continuous source of inoculum for the spring bloom.

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