Moënne-Loccoz, Y. | bioRxiv Science

bioRxiv2024

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

Since the 1980s, soils in a 22-km2 area near Lake Neuchatel 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 insect Oulema melanopus. Plants grown in the most suppressive soil have a reduced stress response to Oulema feeding, 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.

plant biology↗

bioRxiv2018

The effect of susceptible and resistant potato cultivars on bacterial communities in the tuberosphere of potato in soil suppressive or conducive to common scab disease

Connections between the structure of bacterial communities in suppressive soils and potato resistance to common scab (CS) are not well understood. In this study, one resistant and one susceptible cultivar were grown in a conducive and suppressive field to assess cultivar resistance x soil suppressiveness interactions. The resistant cultivar had a higher Mg content in periderm compare to susceptible cultivar, while suppressive soil had lower pH (5.3 vs 5.9), N, C, P, Ca contents but higher Fe and S compared with the conducive soil. Bacteria and actinobacteria numbers were higher in the conducive soil. Copy numbers of txtB gene (coding for a pathogenicity determinant) were similar in both soils but were higher in the conducive soil (for periderm samples) and in the susceptible cultivar (for conducive soil samples). Taxonomic microarray analysis and Illumina sequencing of 16S rRNA genes amplicon showed that bacterial community differed between resistant vs susceptible cultivar and to a lesser extend between suppressive vs conducive soil. Bacteria participating in soil suppression belonged to Pseudomonadaceae, Bradyrhizobiaceae, Acetobacteraceae and Paenibacillaceae, while resistant cultivars selected a bacterial community resembling that of the suppressive soil, which was enriched in Nitrospirae and Acidobacteria. Thus, the analysis of soil suppressivenessxcultivar resistance interactions enabled to gain new insight to CS control in the field.\n\nIMPORTANCEIt was demonstrated that potato cultivars susceptible and resistant to common scab select differing bacterial community and above that this trait is further modified in suppressive and conducive soil. Common scab severity was diminished by either resistant cultivar or suppressive soil but without additive effect between them. Out of the two factors, potato cultivar had a more significant influence on tuberosphere bacterial community composition than soil. Results highlighted the usefulness of both cultivar resistance and soil suppressiveness traits in understanding and managing disease control of crops.

microbiology↗