Beneficial and pathogenic plant‐microbe interactions during flooding stress

Abstract

The number and intensity of flood events will likely increase in the future, raising therisk of flooding stress in terrestrial plants. Understanding flood effects on plantphysiology and plant‐associated microbes is key to alleviate flooding stress insensitive species and ecosystems. Reduced oxygen supply is the main constrain tothe plant and its associated microbiome. Hypoxic conditions hamper root aerobicrespiration and, consequently, hydraulic conductance, nutrient uptake, and plantgrowth and development. Hypoxia favours the presence of anaerobic microbes inthe rhizosphere and roots with potential negative effects to the plant due to theirpathogenic behaviour or their soil denitrification ability. Moreover, plant physiologi-cal and metabolic changes induced by flooding stress may also cause dysbioticchanges in endosphere and rhizosphere microbial composition. The negative effectsof flooding stress on the holobiont (i.e., the host plant and its associated microbiome)can be mitigated once the plant displays adaptive responses to increase oxygenuptake. Stress relief could also arise from the positive effect of certain beneficialmicrobes, such as mycorrhiza or dark septate endophytes. More research is neededto explore the spiralling, feedback flood responses of plant and microbes if we wantto promote plant flood tolerance from a holobiont perspective.