Disease suppressive soils vary in resilience to stress

Soil-borne plant diseases are a major source of crop losses. Biologically active soils have the ability to suppress pathogenic infections of plants, but little is known how this essential soil function might be affected by abiotic stresses. Using a model system with pea and its fungal pathogen Pythium ultimum we studied how the suppressiveness of different soils from a wide geographic range responds to combined heat and drought stress. We found that different soils strongly differ in their ability to suppress diseases and that a stress event of combined heat (40 °C) and drought (−50% moisture) can strongly reduce this disease suppressiveness. Further, the response of suppressiveness to the stress depended on the provenance of the soil. Soils from a cool-climate site in Scotland were much more negatively affected than soils from warmer sites in Germany and Hungary. After being exposed to stress, one soil was able to regain suppressiveness after several weeks while the others were not, thereby collectively showing different degrees of resilience to the stress. Stress tolerance was negatively related to resilience. Our results suggest that microbial communities responsible for suppressiveness are adapted to prevailing climate, which has potentially severe consequences for the impact of climate change upon plant health.