Effects of seedling-stage LED supplementary lighting on the eating quality and textural properties of oriental melon (Cucumis melo L. var. makuwa Makino) fruits at maturity

Introduction: Makino) in cultivation. Although LED supplemental lighting is commonly used to alleviate low-light stress in horticulture, its long-term programming effects on fruit quality remain largely unknown. Methods: This study investigated whether early light signals from different LED spectra (red:blue ratios of 1:1 and 5:1) and intensities (full‑spectrum white at 18, 48, and 60 W) could persistently shape the texture and eating quality of mature fruits in two cultivars, 'Green Gem' and 'Young White Lady'. Seedling-stage lighting treatments were applied, and subsequent fruit quality parameters-including perceived sweetness, fruit firmness, total soluble solids (TSS), titratable acidity (TA), and sugar-acid ratio-were measured. Results: Key cultivar‑specific programming effects were identified. For 'Green Gem', seedling‑stage lighting with R:B = 5:1 at 18 W most effectively enhanced perceived sweetness and fruit firmness. For 'Young White Lady', full‑spectrum light at 48 W optimally boosted TSS (11.9 ± 1.5 °Brix), while 60 W reduced TA, yielding a superior sugar‑acid ratio (95.5 ± 7.0). Additionally, a high R:B ratio strongly correlated with increased acidity (ρ = 0.579). Discussion: These findings reveal a trade‑off between flavor and texture, as high R:B ratios promote acidity but may affect other quality attributes. Seedling‑stage spectral management offers an energy‑efficient strategy for precision quality control in protected horticulture.