Physiological indicators associated with drought tolerance and post-drought recovery in tall fescue

Defining the metabolic strategies employed by tall fescue to withstand and recover from drought events will be crucial for maintaining the performance and stability of turf and forage aspects in the future; however, research on this vital topic is scarce. This study assessed 142 tall fescue genotypes for forage production, physiological, and biochemical responses under two irrigation regimes from 2019 to 2021. In 2022, a two-month drought was imposed to evaluate post-drought recovery. Drought stress decreased photosynthetic pigments (5.26-27.89%) and yield (18.40-34.16%) in tall fescue genotypes. Simultaneously, antioxidant enzyme activities (catalase, ascorbate peroxidase, peroxidase) increased by 40%, 28%, and 31%, respectively, and osmo-protectants increased by 48.88-67.74%. Genetic variation among genotypes indicates potential for drought tolerance selection. The research demonstrates that drought tolerance and recovery in tall fescue are genetically variable and heritable, enabling selection for improved breeding. Under drought, catalase, ascorbate peroxidase, peroxidase, chlorophyll content, and proline can enhance forage yield. However, under control conditions, plant height and crown diameter predict yield in control conditions. Post-drought recovery relates to carbohydrate accumulation and antioxidant enzyme activity; genotypes 6 and 9 showed 20% higher recovery rates. Twenty-one top genotypes (12, 105, 3, 40, 1, 104, 4, 22, 86, 2, 11, 96, 5, 94, 88, 9, 89, 64, 106, 100, and 18) are highlighted for their productivity and drought resilience. Biochemical and physiological markers facilitate early drought tolerance screening, while this study's novelty lies in its integrated physiological, biochemical, and genetic approach.