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<p>Bermudagrass (<i>Cynodon dactylon</i>) is a C4 perennial forage grass of arid and semi-arid regions, but its secondary-metabolite responses across graded salinity and drought intensities remain poorly resolved. In this context, we characterised the dose-dependent phytochemical and antioxidant responses of two contrasting genotypes and tested whether a locally adapted ecotype differs from a commercial cultivar in stress-related metabolite accumulation. In a greenhouse pot experiment, the commercial cultivar 'Gobi' and a locally collected Iğdır (Türkiye) ecotype were exposed to six NaCl levels (0–500&#xa0;mM) and five levels of soil water deficit (25–95% of plant-available water depleted; AWD-25-AWD-95). In the study, seven traits were quantified: condensed tannins (CT), saponins (SAP), total phenolics (TPC), total flavonoids (TFC), total soluble sugars (TSS), DPPH radical-scavenging activity and IC₅₀, and analysed by two-way factorial ANOVA (genotype × stress). The findings of the present study clearly revealed that the genotype × stress interaction was significant for all seven traits (<i>p</i> &lt; 0.01). Saponins were the trait most strongly affected by water deficit, declining from 356.9 to 203.2&#xa0;µg diosgenin-equivalents g⁻<sup>1</sup> DW in 'Gobi' (F = 704.82), whereas salinity most strongly modulated antiradical capacity. Under severe drought the Iğdır ecotype accumulated more total soluble sugars than 'Gobi' (15.7% vs 10.9% DW at AWD-95). Condensed tannins remained within the safe forage range (6.1–10.2&#xa0;g&#xa0;kg⁻<sup>1</sup> DW) under all treatments. Principal component analysis separated low- from high-stress samples along a saponin-phenolic-IC₅₀ axis and positioned the Iğdır ecotype in a sugar-dominated region, indicating an osmotic-adjustment strategy distinct from the phenolic- and flavonoid-based antioxidant strategy of 'Gobi'. In conclusion, the two genotypes employ divergent, stress-specific biochemical strategies; the locally adapted ecotype combines stronger osmotic adjustment with stable, nutritionally safe tannin concentrations, identifying it as a promising resource for stress-tolerant forage breeding and for the management of saline and water-limited pastures.</p>

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Phytochemical plasticity of Cynodon dactylon under progressive salinity and drought stress: dose–response profiling of secondary metabolites, antioxidant capacity, and forage quality in two contrasting genotypes

  • 期刊论文

  • 发表日期：

    2026年7月8日

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  • Recep Akis,
  • Suleyman Temel,
  • Muhittin Kulak,
  • Bilal Keskin,
  • Seda Akbay Tohumcu,
  • Zeynep Nergiz Şeren

摘要

Bermudagrass (Cynodon dactylon) is a C4 perennial forage grass of arid and semi-arid regions, but its secondary-metabolite responses across graded salinity and drought intensities remain poorly resolved. In this context, we characterised the dose-dependent phytochemical and antioxidant responses of two contrasting genotypes and tested whether a locally adapted ecotype differs from a commercial cultivar in stress-related metabolite accumulation. In a greenhouse pot experiment, the commercial cultivar 'Gobi' and a locally collected Iğdır (Türkiye) ecotype were exposed to six NaCl levels (0–500 mM) and five levels of soil water deficit (25–95% of plant-available water depleted; AWD-25-AWD-95). In the study, seven traits were quantified: condensed tannins (CT), saponins (SAP), total phenolics (TPC), total flavonoids (TFC), total soluble sugars (TSS), DPPH radical-scavenging activity and IC₅₀, and analysed by two-way factorial ANOVA (genotype × stress). The findings of the present study clearly revealed that the genotype × stress interaction was significant for all seven traits (p < 0.01). Saponins were the trait most strongly affected by water deficit, declining from 356.9 to 203.2 µg diosgenin-equivalents g⁻1 DW in 'Gobi' (F = 704.82), whereas salinity most strongly modulated antiradical capacity. Under severe drought the Iğdır ecotype accumulated more total soluble sugars than 'Gobi' (15.7% vs 10.9% DW at AWD-95). Condensed tannins remained within the safe forage range (6.1–10.2 g kg⁻1 DW) under all treatments. Principal component analysis separated low- from high-stress samples along a saponin-phenolic-IC₅₀ axis and positioned the Iğdır ecotype in a sugar-dominated region, indicating an osmotic-adjustment strategy distinct from the phenolic- and flavonoid-based antioxidant strategy of 'Gobi'. In conclusion, the two genotypes employ divergent, stress-specific biochemical strategies; the locally adapted ecotype combines stronger osmotic adjustment with stable, nutritionally safe tannin concentrations, identifying it as a promising resource for stress-tolerant forage breeding and for the management of saline and water-limited pastures.