Interactions between soil source, flooding, and herbivory shape tomato plant volatile emissions and rhizosphere bacterial and fungal communities

Abstract Background Plants are exposed to diverse abiotic and biotic stressors during their lifecycle, including flooding and insect herbivory. To mitigate stressors, plants utilize several “cry for help” strategies, including producing volatile organic compounds (VOCs) aboveground and modifying microbial communities belowground. Although we have built strong understanding of plants “cry for help” strategies to individually occurring stressors, our knowledge about how these strategies are impacted by simultaneously-occurring stressors remains limited. Aims We examined the effects of flooding, insect herbivory, and their combination on aboveground VOC emissions and belowground rhizosphere bacterial and fungal communities and assessed how soil source influences these “cry for help” plant strategies. Methods In a greenhouse experiment, tomato plants grown in four soils sourced from different locations were subjected to treatments representing a full factorial combination of ± flooding and ± herbivory by Manduca sexta . VOCs were collected using the solid phase micro-extraction (SPME) technique, and plant growth parameters were recorded. Soil physicochemical characteristics were examined. Bacterial and fungal rhizosphere community changes were assessed using 16S rRNA amplicon sequencing and sequencing of the fungal ITS2 region respectively. Results Flooding was the primary driver of VOC emissions. The stress combination of flooding and insect herbivory significantly increased total VOCs. Soil characteristics, particularly iron, manganese, and ammonium nitrogen shaped VOCs profiles. Belowground, soil source was the dominant factor shaping bacterial and fungal communities. Conclusion Interactions between soil source, flooding, and insect herbivory shape above and belowground tomato plant “cry for help” strategies.