Pear Scab Disease Suppression by Pseudomonas capeferrum NFX1 Is Mediated by Direct Antagonism Against Venturia pyrina and Pear Defense Priming.

Pear scab, caused by Venturia pyrina, poses a threat to pear cultivation, with particularly severe consequences for Portugal's high-value Rocha pear industry. Despite its economic impact, few biological control agents are currently available. In this work, the phenotypic and genomic characterization of Pseudomonas capeferrum NFX1 is performed and its role as an effective biocontrol agent against V. pyrina is reported. Detailed genomic analysis revealed that strain NFX1 and other members of the Pseudomonas capeferrum species contain key biosynthetic gene clusters involved in pathogen antagonism, including the cyclic lipopeptide putisolvin. Phenotypic assays showed that strain NFX1 significantly inhibited V. pyrina growth, spore germination, and reduced pear scab lesion severity and fungal colonization in detached leaf assays. Moreover, strain NFX1 reprogrammed the Rocha pear leaf transcriptome to be consistent with a priming state and induced systemic resistance. A novel image-based method quantifying lesion darkening as a proxy for pear scab severity in detached leaves and a qPCR assay targeting the V. pyrina ef1-α gene and optimized for fungal DNA detection in infected pear leaves were also developed, thereby establishing a laboratory workflow specifically tailored to biocontrol evaluation against V. pyrina. Ultimately, the obtained results demonstrated the potential of P. capeferrum NFX1 for sustainable pear scab control.