Role of genetic diversity and salicylic acid in drought stress memory of tall fescue

Understanding the concequence of drought stress memory and its interaction with genetic diversity and pollination system is critical for improving resilience in turf and forage grasses like tall fescue. With global warming and the predicted occurrence of frequent drought stresses in the future, little is known about these effects, especially on morphological traits, physiological responses, root characteristics, and spectral reflectance indices (SRIs). This study addresses the knowledge gap by evaluating the effects of drought memory in tall fescue using four parental clones (two drought-sensitive and two drought-tolerant), which were manually controlled to produce four selfed (S₁) and four open-pollinated (OP) genotypes. Over two years, these genotypes were exposed to five moisture treatments: control (C), two treatments with twice applications of drought stress (primary mild drought stress in two different stages and secondary at the end stage, D_1t1D₂ and D_1t2D₂), one severe drought stress treatment (secondary only, D₂), and foliar spray of salicylic acid (SA) under end-stage drought stress (H₂D₂). Selfing induced inbreeding depression, reducing relative water content (RWC), growth, chlorophyll, carotenoid content, catalase activity and root length. Alterations in natural plant mating systems can modify the genetic structure of tall fescue germplasm. Drought memory (D_1t1D₂ and D_1t2D₂) improved RWC, root-to-shoot ratio, and most physiological traits, especially pigment content, particularly in drought-tolerant and OP genotypes. SA treatment was more effective in mitigating drought effects in S₁ than OP. Significant genetic variation in SRIs was observed, indicating their potential as predictive tools physiological traits. These findings provide insights into breeding strategies and highlight the importance of leveraging drought memory and genetic diversity to enhance drought resilience in tall fescue.