Foliar fungal endophyte triggers host ecophysiological and morphological responses to drought and waterlogging

Abstract

Background and Aims: Temperate forage grasses form specific symbiotic relationships with Epichloë spp.fungal endophytes. While this symbiosis is known to enhance drought tolerance, itseffect under waterlogging - a common stressor in rainfed agroecosystem - remainsuncertain. This study investigates the ecophysiological mechanisms by which theLolium multiflorum–E. occultans symbiosis influences drought and waterloggingtolerance strategies, both during the stress period and the subsequent recovery phase.MethodsUsing the dual isotope (¹³C/¹²C and ¹⁸O/¹⁶O) concept, we analyzed the physiologicalresponses of L. multiflorum plants with and without Epichloë under severe drought orwaterlogging, relative to well-watered control conditions (field capacity) for 28 days,followed by a 20-day recovery period. We assessed changes in stomatal conductance(inferred via δ¹⁸Ocel), intrinsic water-use efficiency (iWUE), photosynthesis levels,specific tiller production, and specific root growth.Results: Epichloë-symbiotic plants exhibited increased stomatal conductance while maintainingstable iWUE levels. This combination suggests a higher CO₂ assimilation rate, leadingto increased photosynthesis levels. Additionally, symbiotic plants showed greaterspecific tiller production and root growth. During the recovery phase, they maintainedsuperior tiller growth, indicating a role of Epichloë in carbon allocation and post-stressregrowth.Conclusion: The symbiotic association with Epichloë enhances physiological and morphologicalresponses to water stress, improving plant resilience to extreme moisture conditions.These findings highlight the ecological significance of fungal symbiosis in temperateforage grasses, contributing to improved stress tolerance in natural and agriculturalecosystems.