S. Manulis et al., DISTRIBUTION OF STREPTOMYCIN-RESISTANT STRAINS OF ERWINIA-AMYLOVORA IN ISRAEL AND OCCURRENCE OF BLOSSOM BLIGHT IN THE AUTUMN, Phytoparasitica, 26(3), 1998, pp. 223-230
Following failure in control of fire blight with streptomycin, the dis
tribution of streptomycin-resistant strains of Erwinia amylovora in Is
rael was surveyed. During 1994-1997 109 pear, apple, loquat and quince
orchards were monitored. Streptomycin-resistant strains of E. amylovo
ra were recovered from flowers and from infected branches collected at
18 locations in the Sharon, Galilee and Golan Heights regions. In the
Sharon region all the isolated strains of E. amylovora were streptomy
cin-resistant, whereas in the Galilee and Golan Heights, resistant as
well as sensitive E. amylovora strains were recovered at different loc
ations. In the southern coastal plain no resistance could be detected.
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 Isr
ael is not plasmid-mediated. Fire blight symptoms were observed, for t
he first time, on pear blossoms during the autumn of 1994. A high popu
lation of 2 x 10(6)-6 x 10(7) CFU/flower in the autumn of 1995 and of
1996 was correlated with the appearance of blossom blight symptoms.