Natural soil suppressiveness against soilborne phytopathogens extends to the control of insect pest

Abstract

Since the 1980s, soils in a 22-km2area near Lake Neuchâtel in Switzerland have been recognized for their innate ability to suppress the black root rot plant disease. Their efficacy against insect pests has not been studied. We demonstrate that natural soil suppressiveness also protects plants from the leaf-feeding pest insectOulema melanopus. Plants grown in the most suppressive soil have a reduced stress response toOulemafeeding, reflected by dampened levels of herbivore defense-related phytohormones and benzoxazinoids, and enhanced salicylate levels in plants without the insect indicate defense-priming. The rhizosphere microbiome network of the suppressive soils was highly tolerant to the destabilizing impact of insect exposure. The presence of plant-beneficial bacteria in the suppressive soils along with priming conferred plant resistance to the insect pest, manifesting also in the onset of insect microbiome dysbiosis. This intricate soil-plant-insect feedback extends natural soil suppressiveness from soilborne diseases to insect pests.

Expanding the Pseudomonas diversity of the wheat rhizosphere: four novel species antagonizing fungal phytopathogens and with plant-beneficial properties

“…The four Pseudomonas strains described in this study were isolated from the rhizosphere of wheat ( Triticum aestivum cv. Arina) growing in a previously designed sterile microcosm ( Garrido-Sanz et al, 2023a ), containing a soil extract from a previously sampled Swiss soil [46.884947N, 6.922562E, ( Harmsen et al, 2024 )]. Briefly, wheat seeds were surface disinfected with 4% NaOCl solution, thoroughly rinsed with sterile water and germinated on 1% agar plates as previously described ( Garrido-Sanz et al, 2023a ).…”

“…2 (Oxoid) and 5 g yeast extract (Oxoid)) at 25°C. The four novel Pseudomonas described in this study are part of a larger screening process to characterize wheat-associated bacteria in a naturally disease-suppressive field soil ( Harmsen et al, 2024 ).…”