Genomic Epidemiology of Erwinia amylovora Strains That Caused the Fire Blight Outbreak in Korea

Fire blight, a devastating bacterial disease affecting rosaceous plants such as apples and pears, is caused by Erwinia amylovora. The disease, known for its rapid spread and destructive potential, can lead to severe symptoms and often result in the death of infected plants. In Korea, the observation of E. amylovora was first recorded in 2015, and subsequent dissemination has been noted across the peninsula. We previously determined the genomic characteristics of five Korean E. amylovora strains isolated in 2015, demonstrating a close phylogenetic relationship to a North American lineage. Based on these results, we have now sequenced a collection of 92 E. amylovora genomes from various fire blight cases in Korea spanning from 2016 to 2018. Through the population genomic approach, we explored the genetic diversity among the isolates. Our comprehensive genomic assessment facilitated the reconstruction of phylogenetic relationships, the correlation of genetic and spatial distances, and the inference of the most recent common ancestor of Korean E. amylovora. We conclude that E. amylovora was introduced to Korea several years before the first disease outbreak. Genomic insights obtained from our investigation will be invaluable for understanding the genetic characteristics, geographic spread and evolutionary dynamics of Korean E. amylovora.