Synergistic application of Ascophyllum nodosum, Salix aegyptiaca, and gum arabic improves salt tolerance in Rubia tinctorum

Abstract Salinity in arid and semi-arid regions poses a significant limitation to crop growth. The present study aims to assess the synergistic effects of Ascophyllum nodosum , the bark of Salix aegyptiaca , and gum arabic in mitigating the adverse impacts of salinity stress on Rubia tinctorum . The antibacterial activity of root extracts against Ralstonia solanacearum and Pectobacterium carotovorum was evaluated separately using in silico molecular docking. A simplex lattice design with 14 experimental runs was used to optimize elicitors for physiological, biochemical, and antioxidant responses under salt stress. For all measured parameters, the models exhibited high regression coefficients and were statistically significant. The optimal conditions were established at 0.19 GA, 0.27 S. aegyptiaca, and 0.53 A. nodosum for optimum in FHY 37.63 (g), DHY 4.36 (g), EL 36.13 (%), SPAD 29.97 (%), RWC (%) 88.38, proline 1.91 (mg/g FW), MDA 5.21 (µmol/g FW), TPC 70.41 (mg GA/g FW), TFC 20.43 (mg Qu/g FW), PAL 3.90 (µmol cinnamic acid/g FW), DPPH scavenging activity 82.08 (%), GPX 0.78 (U min -1 g -1 FW), CAT 5.60 (U min -1 g -1 FW), APX 5.91 (U min -1 g -1 FW), alizarin 1.41(mg/g). The results indicated that the root extract effectively inhibited the growth of both bacteria compared to the control. In R. solanacearum and P. carotovorum, PDB: 5NMP and 4ZA2 exhibited notable affinities with ligand combinations, respectively. The synergistic models enhanced the potential effectiveness of the treatments and can help R. tinctorum reduce the adverse effects of salinity stress. The optimized formulation remains promising, offering significant and strategic potential for mitigating the adverse effects of salinity stress.