P-540 - Genetic diversity and dissemination strategies in Xanthomonas translucens pv. translucens populations

Bacterial Leaf Streak (BLS), caused by Xanthomonas translucens pv. translucens (Xtt), is a growing concern for barley producers in North America.  With no chemical management solutions currently available, barley producers have limited options for disease control. Understanding the drivers of diversity in the globally distributed genetic subgroups of Xtt – K0, K1, and K2 – will elucidate the disease epidemiology and inform management strategies. Surveys of barley breeder fields in Idaho were conducted in the summers of 2022, 2023, and 2024 to monitor the genetic diversity of the Xtt population and assess subgroup dynamics. Over the three years, K1 and K2 subgroups were more prevalent compared to K0. The overall proportion of subgroups remained stable over the years, with minimal variation observed across sampling locations. Multiple Xtt subgroups were detected within individual BLS lesions, mirroring the distribution patterns observed in the fields. Isolates were ice nucleation active, allowing for ice formation catalysis and precipitation for long distance travel via air systems.  Various factors may drive this diversity, including pathogen virulence and fitness, plant genetics, and environmental transmission. Understanding the relationship between plant and bacterial genetics can provide insights into epidemic development and aid in predicting disease outbreaks. This study provides a model for understanding the drivers of bacterial population distributions and will assist in guiding barley breeders and producers in developing effective disease management strategies.