Kiwifruit Xylem Sap Promotes Pseudomonas syringae pv. actinidiae Proliferation and Vascular Colonization.

Kiwifruit xylem sap supports Pseudomonas syringae pv. actinidiae proliferation and virulence traits, reaching about 10^9 CFU·g^-1 during vascular migration.

• Why it matters: Understanding how Psa proliferates within the nutrient-poor xylem environment is crucial for managing kiwifruit bacterial canker, yet the mechanisms behind systemic colonization remain unclear.
• What they did: The study combined histopathology, metabolomics, bacterial growth kinetics, and gene-expression analyses to investigate Psa behavior in kiwifruit xylem sap from different cultivars, using ex vivo bacterial growth assays and a synthetic medium with key nutrients.
• The result: Xylem sap from both cultivars supported comparable bacterial growth and induced virulence gene expression, indicating it provides a permissive environment, while host defenses and pathogen containment likely influence systemic infection outcomes.