Control of fire blight through systemically acquired resistance and intraspecies characterization of Erwinia amylovora

grantor: University of Toronto'Ophiostoma ulmi' and 'Verticillium dahliae' elicitors were tested for efficacy against 'Erwinia amylovora', causal agent of fire blight, in apple and pear cultivars. Despite inconsistent disease control in apple seedlings with 'O. ulmi' elicitors, both elicitors provided significant protection against 'E. amylovora ' in 4 year-old apple and pear trees ('P' < 0.05). ' E. amylovora' intraspecies differences in extracellular protease production and PCR products of the 16S/23S rDNA intergenic transcribed spacer (ITS) region were also assessed for correlation with host species-specificity. Both ' Maloideae' and 'Rubus' isolates secreted an extracelluar protease of similar size and activity. The ITS PCR products of 'Maloideae ' and 'Rubus E. amylovora' isolates encoded for tRNA Ala and tRNAGlu, and shared significant homology. The smallest ITS PCR product of 'E. amylovora Rubus' isolate 1-97 was homologous with the ITS region of 'E. pyrifoliae', contradicting previous conclusions that 'E. amylovora' and 'E. pyrifoliae ' were not homologous in the ITS region.M.Sc.F