Integrated application of phosphite, phosphate, and arbuscular mycorrhizal fungi enhances postharvest longevity and quality of cut rose (Rosa hybrida cv. Dolce Vita) in soilless culture

This one-year study evaluated the effects of integrated chemical (phosphate and phosphite) and biological (arbuscular mycorrhizal fungi; AMF) biostimulants on the postharvest performance of cut Rosa hybrida cv. Dolce Vita grown in soilless culture. The experiment was conducted as a factorial arrangement in a completely randomized design (CRD) with 29 phosphorus treatments applied via nutrient solution and foliar spray under both AMF-inoculated and non-inoculated conditions, with four replications per treatment. Preliminary optimization using response surface methodology (RSM) identified 17 treatments with the highest overall desirability for enhancing soluble sugars, total chlorophyll, protein, phenolics, and flavonoids. Postharvest analyses revealed that combined potassium-phosphite and phosphate treatments with AMF significantly improved relative solution uptake (RSU, 18-29%; P < 0.01), relative fresh weight (RFW, 21-28%; P < 0.01), and chlorophyll index (CI, 22-27%; P < 0.01), while reducing ion leakage, malondialdehyde (MDA), and hydrogen peroxide (H₂O₂) accumulation compared to the control. Biochemical assays showed increases in soluble protein (up to 1.84 mg g⁻¹ FW), soluble sugars (up to 2.92 mg g⁻¹ FW), total phenolics (up to 2.99 mg gallic acid g⁻¹ FW), flavonoids (up to 0.384 mg quercetin g⁻¹ FW), and enhanced activities of phenylalanine ammonia-lyase (PAL) and antioxidant enzymes (CAT, APX, GPX, SOD; P < 0.01). Gene expression analyses confirmed upregulation of PAL and SOD, supporting enzymatic and molecular defense activation. These integrated treatments effectively delayed senescence, reduced neck bending, and extended vase life from 21 days in the control to 29 days in the optimal treatment (25% potassium-phosphite in nutrient solution combined with 50:50 foliar phosphate/phosphite plus AMF). Overall, the combined application of phosphite, phosphate, and AMF enhances physiological, biochemical, and molecular resilience in cut roses, providing a practical approach for improving postharvest quality.