Isolation and Characterization of Aphanomyces Euteiches Antagonistic Bacteria from Pea Root and Rhizosphere Soil.

Aphanomyces root rot is a serious disease of pea (Pisum sativum L.) worldwide and is becoming one of the major threats to the pea and lentil (Lens culinaris Medik) production in Canada. This oomycete pathogen is not responsive to any known seed treatment agents and no conventional control measures are available for this pathogen. The resting spores of the pathogen can remain active in the soil for more than 10 years under favorable conditions. This project was designed to develop an alternative disease management strategy by identifying antagonistic bacteria toward the suppression of A. euteiches present in field pea roots and rhizosphere soil. The study was initiated by collecting rhizosphere and root samples from diseased and healthy field pea plants from 9 locations across southern Saskatchewan. About six thousand rhizosphere and endophytic bacteria were isolated on Luria Bertani, Potato Dextrose, Pseudomonas, and Tryptic Soy agar media. Bioassays were conducted with 410 selected bacterial isolates under in vitro condition to evaluate their antagonistic potential. Thirty five isolates were selected from the replicated bioassays based on their ability to completely inhibit A. euteiches growth. Ten bacterial isolates were further tested for disease inhibition on field pea under in vitro condition that conferred partial to complete inhibition of root rot development. All 35 bacteria were then tested in a replicated pot experiment in the greenhouse to evaluate their effectiveness in root rot disease suppression of field pea. Twenty four of the 35 bacterial isolates showed promising results in root rot suppression and those isolates are being evaluated further to confirm their antagonism toward A. euteiches. Management of Aphanomyces root rot using antagonistic bacteria may provide a disease management strategy to ensure sustainable and profitable pea production systems in the Canadian prairies.