Fire blight distribution in Georgia and characterization of selected Erwinia amylovora isolates

Since its initial appearance in the Mtskheta-Mtianeti region in 2016, fire blight has spread to several other regions of Georgia during the years 2017–2018, especially affecting the eastern part of the country. The causative agent of the disease, Gram-negative bacterium Erwinia amylovora, was confirmed by PCR in hundreds of instances on different organs of symptomatic apple, quince and pear trees. Isolates recovered from diseased plants in Georgia display the typical biochemical and physiological properties of the species. Sequencing of the CRISPR regions revealed the presence of two distinct genotypes that can directly or indirectly be traced back to those that originally colonized Europe in the second part of the twentieth century. Genetic and phenotypic differences among the isolates analyzed, together with the rapid spread of the disease across the country, are suggestive of multiple introduction events that occurred in recent years through import of diseased plant material