Abstract
<title>Abstract</title> <p> Background Combined abiotic and biotic stresses frequently occur in agricultural systems, yet the physiological mechanisms determining crop performance under stress combinations remain insufficiently understood. Salinity and take-all disease caused by <italic>Gaeumannomyces tritici</italic> are major constraints for wheat production, particularly in salt-affected regions. This study aimed to identify physiological indicators and adaptive strategies associated with wheat performance under simultaneous salinity and pathogen stress. Results Ten bread wheat ( <italic>Triticum aestivum</italic> L.) genotypes were evaluated under control, salinity, <italic>G. tritici</italic> infection, and combined salinity–pathogen conditions using a factorial greenhouse experiment with three replications. Root and shoot K⁺/Na⁺ ratios, peroxidase (POD) activity, phenylalanine ammonia-lyase (PAL) activity, and total soluble protein content were analyzed. Analysis of variance revealed highly significant effects of genotype, treatment, and genotype × treatment interaction for all measured traits (p < 0.001), indicating strong genetic variation in stress adaptation. Under combined stress, genotypes 1528 and 1642 maintained superior ionic balance and antioxidant capacity, particularly through higher K⁺/Na⁺ ratios and POD activity. Principal component analysis showed that the first two components explained 81.8% of total trait variation under combined stress, separating genotypes according to ionic–antioxidant regulation versus metabolic defense strategies. Ward’s cluster analysis further separated 30 genotype–environment combinations into two distinct groups. The first cluster (19 observations) was characterized by positive standardized values for root K⁺/Na⁺ ratio (+ 0.657), shoot K⁺/Na⁺ ratio (+ 0.894), and POD activity (+ 0.395), whereas the second cluster (11 observations) showed higher total protein and PAL activity (+ 0.558 for both traits), representing contrasting physiological strategies. Conclusions The results demonstrate that wheat plants do not rely on a single defense mechanism under combined stress but dynamically shift between ionic–antioxidant regulation and secondary metabolic defense depending on the dominant stress component. Shoot and root K⁺/Na⁺ ratios, together with POD activity, represent promising physiological indicators for identifying wheat genotypes adapted to saline and disease-prone environments. </p>