In Tuber Biocontrol of Potato Late Blight by a Collection of Phenazine-1-Carboxylic Acid-Producing Pseudomonas spp.

Phenazine-1-carboxylic acid (PCA) produced by plant-beneficial Pseudomonas spp. is an antibiotic with antagonistic activities against Phytophthora infestans, the causal agent of potato late blight. In this study, a collection of 23 different PCA-producing Pseudomonas spp. was confronted with P. infestans in potato tuber bioassays to further understand the interaction existing between biocontrol activity and PCA production. Overall, the 23 strains exhibited different levels of biocontrol activity. In general, P. orientalis and P. yamanorum strains showed strong disease reduction, while P. synxantha strains could not effectively inhibit the pathogen’s growth. No correlation was found between the quantities of PCA produced and biocontrol activity, suggesting that PCA cannot alone explain P. infestans’ growth inhibition by phenazine-producing pseudomonads. Other genetic determinants potentially involved in the biocontrol of P. infestans were identified through genome mining in strains displaying strong biocontrol activity, including siderophores, cyclic lipopeptides and non-ribosomal peptide synthase and polyketide synthase hybrid clusters. This study represents a step forward towards better understanding the biocontrol mechanisms of phenazine-producing Pseudomonas spp. against potato late blight.