The Influence of Solar Radiation Modulation Using Double-Roof Light Conversion Films on the Pre- and Post-Harvest Fruit Quality of Strawberry (Fragaria × ananassa cv. Marimbella)

Light conversion (LC®) films represent a novel approach to modulating the light spectra in protected horticulture. The present study evaluated the effects of two LC® polyethylene films on the growth and fruit quality of Fragaria × ananassa ‘Marimbella’ strawberries, cultivated using a soilless system in a double-roof greenhouse from March to June. The following films were used: blue (B), which converts UV to blue light, and pink (P), which converts UV and green light to blue and red wavelengths. These treatments were compared with a transparent film (T) and an uncovered sample (Control). The B film enhanced net photosynthesis (+9%) and stomatal conductance (+11%) compared to the Control, with no effect on intercellular CO2 concentration or PSII efficiency. Under the B film, fruit yield increased by 34 and 44% compared to the Control and T, respectively, although single fruit weight, fruit width, and fruit height decreased. The P film did not significantly influence the yield but improved fruit quality, increasing soluble solids (+30%) and ascorbic acid (+29%) content compared to the Control and T, respectively. At harvest time, both LC® films promoted the accumulation of total phenolic content (+17% vs. T). At the same time, the highest antioxidant activity was observed in Control fruits. Notably, the B film reduced post-harvest Botrytis cinerea development (−37% vs. T) at 72 h after inoculation. These findings highlight the potential of LC®—particularly the B film—to be used as a sustainable tool to improve yield, quality, and post-harvest disease resistance in greenhouse strawberry production systems.