Pathogen local adaptation shapes Pierce's disease of grapevines outcomes under field conditions.

Local Xylella fastidiosa strains in California show 77% lower overwinter survival compared to non-local strains, indicating strong local thermal adaptation in field conditions.

• Why it matters: Understanding pathogen thermal adaptation is crucial for predicting disease spread under climate change, yet it remains poorly characterized in bacterial plant pathogens like X. fastidiosa.
• What they did: A common garden experiment with 477 grapevines across 13 varieties over 3 years compared PD outcomes from local and non-local strains, complemented by whole-genome sequencing of 58 isolates to assess in planta evolution.
• The result: Results reveal local adaptation to cold temperatures and rapid adaptive evolution involving convergent mutations in Type IV pilin genes, highlighting the importance of incorporating thermal adaptation into disease models.