Synergistic effects of zinc and phosphorus on salinity tolerance in potato: Integrating morpho-physiological traits and nutrient transporter gene expression

Abstract The accumulation of salts in the soil acts as a primary barrier to successful potato cultivation, directly hindering vital processes such as photosynthetic activity, overall development, and nutritional equilibrium. This research analyzed how the individual and synergetic application of zinc (Zn) and phosphorus (P) influences the physiological, morphological, molecular, and biochemical reactions of four distinct potato varieties (D6, KG911-91, D220, and KG913) grown in high-salinity environments. Findings confirmed that salt exposure consistently impaired root health, biomass production, and the density of photosynthetic pigments. Nevertheless, the targeted administration of Zn and P—especially when used in tandem—mitigated these stressors and boosted plant vitality. Distinct differences in salt resilience were observed across the genotypes. KG911-91 emerged as the most robust variety, followed by D220, both of which maintained superior osmotic regulation and pigment levels under stress. Conversely, KG913 displayed the highest sensitivity to salt. While genotype D6 demonstrated a significant upregulation of nutrient transporter genes, its stunted growth compared to D220 and KG911-91 suggests that this molecular response was a mere reaction to stress rather than an effective adaptive mechanism. Supplementing these nutrients boosted the synthesis of chlorophyll, soluble sugars, anthocyanins, and carotenoids, thereby reinforcing the plants’ antioxidant defenses, osmotic balance, and photosynthetic efficacy. Statistical analysis via Principal Component Analysis (PCA) revealed that metabolite and pigment profiles were the primary drivers of physiological variance, whereas morphological disparities were largely defined by biomass metrics. On a genetic level, the synchronized expression of StZIP_2179 , StZIP_2151 , and StPHT2 in tolerant varieties—specifically when treated with a combination of Zn and P—facilitated superior nutrient uptake and stress resilience. In summary, this study demonstrates that integrated Zn–P fertilization is an effective method for bolstering salinity tolerance in potatoes. By optimizing nutrient transport, sustaining photosynthesis, and enhancing osmotic performance, this strategy provides a viable pathway for improving crop yields in challenging, salt-stressed agricultural lands.