A simple and easy laboratory technique is suggested for testing virulence of isolates of Erwinia amylovora, the causal of the fire-blight disease of pear and apple. In this work, detached apple or pear leaves were used in spring and summer months for testing virulence in the laboratory. In autumn and winter months, where desired young leaves from these host plants are not available, germinated pear seedlings could be used for this purpose. Seeds were germinated by the removal of the seed coats and directly planted in large trays containing moistened vermiculite. Suitable seedlings for inoculation could be produced within 2 weeks by this technique. These sources of plant material can now make testing virulence of E. amylovora isolates in laboratories, quite easy and satisfactory all the year round. Virulence of different strains could be determined within 48 hours-incubation period in inoculated wounded pear seedlings. Moderately virulent strains did not give any disease reaction at relatively low inoculum densities at this short period of incubation. |
