Isolation, identification, and assessment of soil bacteria as biocontrol agents of pea root rot caused by Aphanomyces euteiches

Abstract

Aphanomyces euteiches is a soil-borne pathogen that causes root rot of pea and can significantly affect pea production in western Canada. This study aimed to isolate and identify soil bacteria with antagonistic activity towards A. euteiches mycelial and zoospore developmental stages under in vitro conditions and assess their potential as biocontrol agents against aphanomyces root rot in field pea under growth chamber conditions. In vitro screening of soil bacteria identified 184 antagonistic isolates, including 22 from an existing culture collection. Mean mycelial growth inhibition zones ranged from 1 to 12 mm, and mean zoospore germination inhibition ranged from 0% to 100%. Use of 16S rDNA sequence analysis placed isolates into 18 different bacterial genera. Screening of 47 bacteria that inhibited both infective stages identified 29 potential biocontrol strains, including Rhizobium spp. that significantly (α = 0.05) suppressed aphanomyces root rot in field pea grown in vermiculite, suggesting the intriguing possibility of using N-fixing Rhizobium inoculants as biocontrol agents for aphanomyces control. Further screening of 20 isolates as soil inoculants identified K-Hf-L9 (Pseudomonas fluorescens), PSV1-7 (Pantoea agglomerans), and K-Hf-H2 (Lysobacter capsici) isolates as having the highest biocontrol activity, significantly (α = 0.05) suppressing aphanomyces root rot in field pea in growth chamber trials. This study demonstrates the possibility of aphanomyces root rot management using biocontrol agents.