Drought-response strategies in arbuscular mycorrhizal symbioses are shaped by inoculum environmental origin

Abstract

Background and Aims.The increasing frequency, intensity, and duration of droughts threaten global forage production and livestock sustainability. Arbuscular mycorrhizal fungi (AMF) are key modulators of plant drought resilience, yet assuming uniform benefits overlooks the potential importance of their environmental origin. We evaluated how the origin of AMF isolates shapes plant ecophysiological strategies to cope with drought and which components of drought resistance are most strongly modulated by symbiosis.Methods. Lolium multiflorum plants were inoculated with five Rhizophagus spp. isolates collected across a broad environmental gradient, from deserts to wetlands, and subjected to drought and recovery cycles. Morphological (aerial biomass, tiller number) and physiological traits (stomatal conductance, leaf greenness, chlorophyll a fluorescence) were measured throughout the experiment. Results.AMF environmental origin significantly influenced plant strategies to cope with and recover from drought. Isolates from humid environments promoted tolerance-leaning responses by maintaining physiological function and protecting PSII, whereas isolates from arid or highly fluctuating environments induced avoidance-leaning strategies characterized by strict stomatal closure and increased thermal dissipation that persisted into the recovery period. Conclusions. This study provides the first evidence that AMF origin induces qualitatively distinct drought-response strategies within a single host species. These findings highlight the importance of selecting AMF based on environmental background to enhance plant resilience and forage productivity under climate change.