Antagonistic soil-borne Bacillus spp. and Pseudomonas spp. bacteria against late blight and other potato pathogens: From the laboratory to the field

Caulier, Simon [UCL] Gillis, Annika [UCL] Colau, Gil [UCL] Licciardi, Florent Liépin, Maxime Desoignies, Nicolas Modrie, Pauline Legrève, Anne [UCL] Mahillon, Jacques [UCL] Bragard, Claude [UCL] et al.[show all]

Today potato remains one of the most pesticide-intensive crop around the world. The control of late blight often request numerous fungicide treatments, raising both economic and environmental concerns. This work aimed at developing indigenous bacteria-based alternatives that could be integrated into sustainable pest management schemes encompassing alternatives such as adapted fertilizations, reasoned rotations or the use of resistant cultivars. About 2,800 Bacillus spp. and Pseudomonas spp. strains were isolated from soils, manure, composts and potato plants in Belgium. Their antagonistic activities were assessed in vitro against five potato pathogens: Alternaria solani, Fusarium solani, Pectobacterium carotovorum, Phytophthora infestans and Rhizoctonia solani. Fifty-two Bacillus spp. and eight Pseudomonas spp. strains, displaying strong in vitro inhibition, particularly against P. infestans, were selected and further characterized. All 60 bacterial isolates were identified based on 16S rRNA gene sequencing and genetically characterized for the production of potential bioactive secondary metabolites. This screening revealed that metabolites such as bacilysin, bio-surfactants and siderophores might explain the activities against late blight. Further greenhouse assays focusing on in vivo antagonistic effect against P. infestans allowed the selection of eleven strains of interest. Those bioassays were followed by a pilot field trial which highlighted one Bacillus subtilis able to significantly decrease late blight severity throughout the crop season. Overall, this study underlines the potential of using antagonistic indigenous soil bacteria as a relevant alternative to the use of pesticides in potato agro-systems.