First report of fire blight on Cotoneaster in China.

In May 2023, characteristic symptoms of fire blight, suspected to be caused by Erwinia amylovora, were observed infected wild Cotoneaster plants in the secondary forest along the lower reaches of the Jilgilang River, Xinjiang, China. Symptomatic tissues were collected, and bacterial isolation and purification were performed. The bacterium was identified through morphological characterization of the colonies, pathogenicity assays, tobacco hypersensitivity tests, and specific polymerase chain reaction (PCR) amplification, followed by sequence analysis. The isolated bacterium exhibited morphological features consistent with E. amylovora, and pathogenicity tests conducted under greenhouse conditions confirmed its pathogenicity, as evidenced by bacterial dissemination from the main leaf veins to surrounding tissues and the presence of bacterial exudates at the petioles. Furthermore, a pronounced hypersensitive response was observed in tobacco. PCR followed by sequencing revealed over 99.6% similarity with E. amylovora plasmid pEa29 repeat region. These findings confirm the E. amylovora is the causal agent of the fire blight disease in wild Cotoneaster plants. This is the first documented case of the fire blight affecting Cotoneaster plants in China. The detection of this pathogen has significant implications for the conservation of wild Rosaceae germplasm in the Tianshan Mountains wild fruit forests in Xinjiang.