Metabolites from wild potato inhibit virulence factors of the soft rot and blackleg pathogen Pectobacterium brasiliense

Potato (Solanum tuberosum L.) is the primary vegetable crop consumed worldwide and is largely affected by bacterial pathogens that can cause soft rot and blackleg disease. Recently, resistance to these diseases has been identified in the wild potato Solanum chacoense, and the mechanism of resistance is unknown. Here, it was hypothesized that S. chacoense stems and/or tubers have unique chemistry that confers resistance to the pathogen Pectobacterium brasiliense through bactericidal, bacteriostatic, and/or anti-virulence activity. Stem and tuber metabolite extracts were collected from S. chacoense and tested for effects on Pectobacterium bacterial multiplication rates, and activity and expression of known exoenzymes and virulence genes using S. tuberosum extracts as a comparative control. Comparatively, the S. chacoense extracts did not affect bacterial multiplication rate, however, did reduce pectinase, cellulase, and protease activities. The chemical extracts were profiled using a bioassay-guided fractionation and a non-targeted metabolomics comparison of S. chacoense and S. tuberosum stems and tubers were performed. The data showed that selected alkaloids, phenolic amines, phenols, amines, and peptides are integrative chemical sources of resistance against the bacteria.