ADAPTIVE POTENTIAL AND BIOCHEMICAL PROFILING OF INTRODUCED WHITE SWEET CLOVER (MELILOTUS ALBUS L.) VARIETIES UNDER ARID SALINE CONDITIONS OF THE KHOREZM REGION, UZBEKISTAN

Abstract

White sweet clover (Melilotus albus L.) is a multipurpose legume valued as a source of coumarins, bioflavonoids, and forage biomass, yet its varietal performance under the extreme agro-ecological conditions of the Khorezm region of Uzbekistan—characterized by high summer temperatures (up to +45 °C), low precipitation (94–100 mm·year⁻¹), and moderate soil salinity (0.4–0.6% total salts)—remains largely unexplored. This three-year study (2024–2026) aimed to comparatively assess the introduction success, morpho-physiological traits, yield potential, and biochemical composition of three introduced white sweet clover varieties (Almaz, Iney, Volzhanin) against the local standard Kibray. Field trials were conducted on moderately saline meadow-alluvial soils of the Khorezm Mamun Academy experimental station (Xiva district). Significant genotypic differences were observed: Volzhanin exhibited the highest field germination rate (92.4%), emergence energy (91.5%), and green biomass yield (40.8 t·ha⁻¹), while Almaz showed superior germination (94.0%) and the highest overall green yield (44.5 t·ha⁻¹). Both varieties demonstrated superior water-holding capacity (47.5% and 46.8% at branching, respectively) and lower water deficit across phenological stages compared to the control. Transpiration rates peaked at midday across all varieties but were notably higher in Volzhanin (up to 2.62 g·m⁻²·h⁻¹), indicating efficient cooling under heat stress. Biochemical analysis revealed Volzhanin as the most promising source of bioactive compounds, accumulating the highest total coumarin content (1.84%, including free and bound forms), dominating in melilotic and o-coumaric acids. It also contained the highest levels of key bioflavonoids—rutin (0.46 mg·100g⁻¹), apigenin-7-glucoside (0.65), isoquercetin (0.72), vitexin (0.78), and kaempferol (0.210). Protein content was highest in Volzhanin (20.5%), followed by Almaz (19.8%), significantly exceeding the control. The varieties Volzhanin and Almaz are recommended for large-scale cultivation as sustainable sources of high-value bioactive compounds and forage biomass in the arid, saline conditions of the Khorezm region.