Two Bermudagrass Genotypes Take Opposite Biochemical Roads to Survive Salt and Drought

Bermudagrass has long been the quiet workhorse of the world’s arid rangelands. A C4 perennial grass that thrives where many forage crops fail, Cynodon dactylon carpets saline flats, drought-prone pastures and degraded soils across vast stretches of the tropics and subtropics. Yet the biochemical machinery that lets this grass endure such punishing conditions has remained surprisingly opaque, particularly when it comes to the secondary metabolites that shape both stress resilience and forage quality. A new greenhouse study published in Plant Biosystems has now mapped those responses in unprecedented detail, and the results reveal that two genotypes of the same species can solve the same environmental problems in strikingly different ways.

Researchers from Iğdır University in Türkiye set out to answer a deceptively simple question: when salinity or drought intensifies, how does the phytochemistry of bermudagrass change, and does a locally adapted wild ecotype respond differently from a commercial cultivar? To find out, they grew the commercial cultivar ‘Gobi’ alongside an ecotype collected from the harsh, semi-arid landscapes of Iğdır province in eastern Türkiye. The plants were subjected to a carefully graded stress regime: six levels of sodium chloride ranging from zero to a punishing 500 millimolar, and five levels of soil water deficit in which between 25 and 95 percent of plant-available water was depleted. This dose–response design, rather than the single-stress snapshots common in the literature, allowed the team to trace how each biochemical trait shifts as stress ramps up incrementally.

The analytical scope was equally ambitious. Seven traits were quantified for every genotype–stress combination: condensed tannins, saponins, total phenolic content, total flavonoid content, total soluble sugars, and antiradical capacity measured through the DPPH radical-scavenging assay and its half-maximal inhibitory concentration, IC₅₀. Two-way factorial analysis of variance tested the genotype-by-stress interaction for each trait, and the outcome was unambiguous. Every one of the seven traits showed a statistically significant interaction at the p < 0.01 level, meaning that the way each genotype responded chemically depended on both the type and the intensity of the stress it faced. There was no single, universal stress chemistry; instead, each genotype deployed its own tailored arsenal.

Perhaps the most dramatic single finding concerned saponins, the soap-like glycosides that plants use in defence and that can affect rumen metabolism in grazing animals. Water deficit proved to be the dominant driver of saponin dynamics. In the ‘Gobi’ cultivar, saponin concentrations collapsed from 356.9 to 203.2 micrograms of diosgenin equivalents per gram of dry weight as drought intensified, an effect so strong that the corresponding F-value reached 704.82, an extraordinarily large test statistic for a plant chemistry experiment. The steepness of this decline suggests that saponin biosynthesis is either an energetically expensive luxury the cultivar abandons under water stress or a trait tightly regulated by drought-responsive signalling pathways. Either way, the drop represents one of the clearest dose-dependent secondary metabolite responses documented in this species.

Salinity told a different story. While drought reshaped saponins, salt stress most strongly modulated antiradical capacity, the plant’s ability to neutralise the reactive oxygen species that accumulate when sodium and chloride ions disrupt photosynthesis and cellular metabolism. This distinction matters because it implies that the two stresses are not interchangeable in their biochemical consequences. A breeder selecting for salt tolerance would therefore be screening a different suite of traits than one selecting for drought tolerance, even within the same species. The finding echoes a broader principle in plant stress physiology: salinity imposes both osmotic and ionic burdens, and the antioxidant arm of the response, heavily dependent on phenolic and flavonoid compounds, appears to be the most sensitive barometer of that ionic pressure.

Under the most severe drought treatment, when 95 percent of plant-available water had been depleted, the Iğdır ecotype revealed its signature strategy. It accumulated markedly more total soluble sugars than ‘Gobi’, reaching 15.7 percent of dry weight compared with the cultivar’s 10.9 percent. Soluble sugars are classic compatible solutes: small, non-toxic molecules that accumulate in cells to maintain osmotic pressure and protect proteins and membranes when water becomes scarce. The ecotype’s sugar-heavy profile points to a robust osmotic adjustment strategy, an adaptation plausibly forged by generations of natural selection in the water-limited landscapes around Iğdır. The commercial cultivar, by contrast, leaned on a phenolic- and flavonoid-based antioxidant strategy, investing in radical-scavenging chemistry rather than osmotic buffering.

Principal component analysis made this divergence visually striking. When the researchers projected all samples onto the plane defined by the first two principal components, low-stress and high-stress samples separated cleanly along an axis loaded with saponins, phenolics and IC₅₀, while the Iğdır ecotype occupied a distinct region dominated by soluble sugars. In effect, the ordination plot drew a biochemical map of two survival philosophies: one genotype fights oxidative damage with defensive phenolics, the other rides out water scarcity with osmotic sugars. That such clear separation emerged from a single species underscores how much hidden adaptive variation can reside within the gene pool of even a familiar forage grass.

Crucially for livestock producers, none of this stress chemistry compromised feed safety. Condensed tannins, compounds that bind proteins and can depress digestibility at high concentrations while offering bloat reduction and even methane mitigation at moderate levels, remained within the safe forage range across every treatment, fluctuating between 6.1 and 10.2 grams per kilogram of dry weight. This narrow, nutritionally benign window held under both salinity and drought, in both genotypes. For a grass destined to feed ruminants on marginal land, the stability of tannin levels is arguably as important as any stress-tolerance trait, because it means the forage quality of bermudagrass pastures is unlikely to deteriorate into anti-nutritional territory even as climate stress intensifies.

The broader context gives these findings real urgency. The FAO’s 2024 global assessment of salt-affected soils documents the relentless spread of salinisation across agricultural land, while climate projections point to more frequent and severe drought episodes in the very regions where forage grasses must carry livestock production. Bermudagrass, already renowned for its salinity tolerance among C4 grasses, is a natural candidate for breeding programmes aimed at these converging pressures. What the new study adds is a biochemical roadmap: it identifies osmotic adjustment capacity, antioxidant phenolic profiles and stable tannin concentrations as measurable targets, and it demonstrates that wild ecotypes can carry trait combinations that commercial cultivars lack.

The Iğdır ecotype emerges from the analysis as the standout genetic resource. It combines stronger osmotic adjustment, evidenced by its superior sugar accumulation under extreme drought, with tannin levels that stayed safely within forage-quality limits throughout the experiment. The authors conclude that this locally adapted genotype represents a promising donor for stress-tolerant forage breeding and a model for managing saline and water-limited pastures. In an era when agricultural margins are being pushed onto land that conventional crops increasingly cannot occupy, the lesson from this humble Turkish grass is a compelling one: sometimes the best solutions to tomorrow’s agricultural problems are already growing, quietly and unassumingly, in the world’s harshest landscapes, waiting for science to read their chemistry.

Subject of Research: Dose-dependent secondary metabolite and antioxidant responses of two Cynodon dactylon genotypes to graded salinity and drought stress

Article Title: 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

Article References: Akis, R., Temel, S., Kulak, M., Keskin, B., Tohumcu, S. A., & Şeren, Z. N. (2026). 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. Plant Biosystems, 160(4), Article 219. https://doi.org/10.1007/s44473-026-00233-2

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00233-2

Keywords: bermudagrass, Cynodon dactylon, salinity stress, drought stress, secondary metabolites, saponins, condensed tannins, antioxidant capacity, osmotic adjustment, forage quality, plant breeding, abiotic stress