Phenazine-1-carboxylic acid production by Pseudomonas fluorescens LBUM636 alters Phytophthora infestans’ growth and late blight development
A. NOVINSCAK (1), M. Filion (1), C. Morrison (1) (1) Université de Moncton, Canada

Phytophthora infestans causes late blight of potato, one of the most devastating diseases affecting potato production. Alternative approaches for controlling late blight are being increasingly sought due to increasing environmental concerns and P. infestans resistance to chemical pesticides. Our research group has isolated a new strain of Pseudomonas fluorescens (LBUM636) of biocontrol interest due to its production of the antibiotic phenazine-1-carboxylic acid (PCA). Wild-type LBUM636 was shown to significantly inhibit the growth of P. infestans in in vitro confrontation assays while its isogenic mutant (phzC-; not producing PCA) barely altered the pathogen’s growth. Wild-type LBUM636, but not the phzC- mutant, also completely repressed disease symptom development on tubers. Pot experiments in growth chambers revealed that wild-type LBUM636 can significantly reduce P. infestans populations in the rhizosphere and in the roots of potato plants, as well as reduce in planta disease symptoms due to PCA production. The expression of eight common plant defense-related genes (ChtA, PR-1b, PR-2, PR-5, LOX, PIN2, PAL-2, and ERF3) was quantified in tubers, roots and leaves by RT-qPCR and revealed that the biocontrol observed was not associated with the induction of a plant defense response by LBUM636. Instead, a direct interaction between P. infestans and LBUM636 is required and PCA production appears to be a key factor for LBUM636’s biocontrol ability.

Abstract Number: P5-125
Session Type: Poster