Genomic Biosurveillance of the Kiwifruit Pathogen Pseudomonas syringae pv. actinidiae Biovar 3 Reveals Adaptation to Selective Pressures in New Zealand Orchards

• DOI: 10.1111/mpp.70056
• Publication Date: 2025-02-07T05:49:11Z
• Authors: Lauren M. Hemara; Stephen M. Hoyte; Saadiah Arshed; Magan M. Schipper; Peter N. Wood; Sergio L. Marshall; Mark T. Andersen; Haileigh R. Patte...; Joel L. Vanneste; Linda Peacock; Jay Jayaraman; Matthew D. Templeton
• Keywords: Pseudomonas syringae; Biovar; Actinidia

In the late 2000s, a pandemic of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) devastated kiwifruit orchards growing susceptible, yellow-fleshed cultivars. New Zealand's industry has since recovered, following deployment tolerant cultivar 'Zesy002'. However, little is known about extent to which Psa population evolving its arrival. Over 500 Psa3 isolates from Zealand were sequenced between 2010 and 2022, commercial monocultures diverse germplasm collections. While effector loss was previously observed on Psa-resistant vines, appears be rare in orchards, where dominant cultivars lack resistance. new variant, lost hopF1c, arisen. The hopF1c have been mediated by movement integrative conjugative elements introducing copper resistance into this population. Following variant's identification, in-planta pathogenicity competitive fitness assays performed better understand risk likelihood spread. variants had similar growth wild-type Psa3, lab-generated ∆hopF1c strain could outcompete wild type select hosts. Further surveillance conducted these originally isolated, with 6.6% surveyed identified as variants. These findings suggest that spread currently limited, they are unlikely cause more severe symptoms than current Ongoing genome biosurveillance recommended enable early detection management interest.