Tall wheatgrass [Elymus elongatus subsp. ponticus (Podp.) Melderis] is a perennial forage grass cultivated in dry, saline or alkaline environments. The morpho-physiological characteristics of four populations of tall wheatgrass from different climatic-edaphic origins were evaluated under three conditions of water stress (100%-50%-30% of field capacity). The trial was analyzed with three replicates and two-factor ANOVA in pots within the greenhouse during 35 days. Only dry matter and tiller number showed interaction between populations and water conditions. The most relevant changes in morpho-physiological parameters under strong water stress were reduced dry matter production (48–32% differing among populations), smaller leaf and tiller size (46% and 28%), together with higher water use efficiency (74%), and increased proline and protein contents (144% and 71%), smaller tiller number (30–11% differing among populations) and a slight decrease in leaf water content (3%). The populations differed in growth strategies and morpho-physiological mechanisms to survive water stress, which could be related to their habitat background. The study shows the stability in dry matter production under all levels of water stress, which can be related to the higher tiller number. Due to this plasticity, tall wheatgrass should be studied as a species with great potential to adapt to drought stress.

Tall wheatgrass [Elymus elongatus subsp. ponticus (Podp.) Melderis] is a C3 grass native from dry or saline habitats in SE Europe. The aim of this study was to better understand response mechanisms of populations from different origins to salinity and to provide new tools to select germoplasm with high salinity tolerance. Four populations (P3‐P4‐P5‐P9) were irrigated with five solutions of increasing salinity (Salt: 0–0.1–0.2–0.3–0.4 M NaCl) and evaluated in pots in a greenhouse. Two experiments were carried out, a short 40‐day long experiment with vegetative plants, and a longer 85‐day long one with plants that underwent vegetative‐reproductive stage. No evidence was found of an interaction between population and salt. Morpho‐physiological, biochemicals, isotopic and productive variables were differently affected by increasing salinity and were also different among populations. Proline, Na+ and Cl− consistently appeared to function as osmotic agents. P5 showed the highest biomass in the 85‐day experiment and had the highest leaf length, tiller density, water use efficiency and δ13C isotope; and the lowest Cl− concentration and evapotranspiration rate. However, P5 showed the lowest biomass in the 40‐day experiment, suggesting that duration of the stress is an important aspect to consider when selecting germoplasm for tolerance to salinity. Differences among populations in growth strategies and physiological mechanisms could be related to their origin environment.

Tall wheatgrass (Thinopyrum ponticum (Podp.) Barkworth and D.R. Dewey) is an important, highly salt-tolerant C3 forage grass. The objective of this work was to learn about the ecophysiological responses of accessions from different environmental origins under drought and salinity conditions, to provide information for selecting superior germplasm under combined stress in tall wheatgrass. Four accessions (P3, P4, P5, P9) were irrigated using combinations of three salinity levels (0, 0.1, 0.3 M NaCl) and three drought levels (100%, 50%, 30% water capacity) over 90 days in a greenhouse. The control treatment showed the highest total biomass, but water-use efficiency (WUE), δ13C, proline, N concentration, leaf length, and tiller density were higher under moderate drought or/and salinity stress than under control conditions. In tall wheatgrass, K+ functions as an osmoregulator under drought, attenuated by salinity, and Na+ and Cl− function as osmoregulators under salinity and drought, while proline is an osmoprotector under both stresses. P3 and P9, from environments with mild/moderate stress, prioritized reproductive development, with high evapotranspiration and the lowest WUE and δ13C values. P4 and P5, from more stressful environments, prioritized vegetative development through tillering, showing the lowest evapotranspiration, the highest δ13C values, and different mechanisms for limiting transpiration. The δ13C value, leaf biomass, tiller density, and leaf length had high broad-sense heritability (H2), while the Na+/K+ ratio had medium H2. In conclusion, the combined use of the δ13C value, Na+/K+ ratio, and canopy structural variables can help identify accessions that are well-adapted to drought and salinity, also considering the desirable plant characteristics. Tall wheatgrass stress tolerance could be used to expand forage production under a changing climate.