S06 - Session P7 - The effect of far-red light on white or pink supplemental LED lighting on growth and development of June-bearing strawberries

Authors: Theoharis Ouzounis *, Lisanne Helmus-Schuddebeurs, Stijn Jochems, Caroline Labrie, David Hawley

To meet strawberry year-round demand, greenhouse growers use many methods for out-of-season strawberry production, with supplemental LED lighting being one of them. Strawberry cultivars, like other plants, vary in their responses to different light spectra. Far-red (FR) light, through the light-sensing phytochrome proteins, has been shown to affect crop morphology and development, flowering, photosynthesis, and metabolism. The solar red to far-red ratio (R:FR) can vary depending on time of day, weather conditions, and season. Therefore, adding far-red light on top of the photosynthetically active radiation (PAR) has been a common practice, however, it is not clear if the potential benefits stem from FR signaling or the additional intensity itself. To decouple this, we grew two 'June-bearing' cultivars, Sonata and Sonsation, under 4 different LED treatments: 1) White, 2) White-FR, 3) Pink and 4) Pink-FR. All of the light treatments were at the level of 200 PFD (μmol m -2 s -1 ), with FR being a part of the 200 PFD and not added on top of the PAR. The strawberries were grown from October 2020 to March 2021, therefore covering the whole period of the 1 st flush. Morphological and developmental parameters, such as plant height, leaf area, and fruit yield, were measured. In addition, since strawberries have high nutritional value and health benefits, fruit quality attributes were also recorded. Besides TSS (Brix) values, a sensory panel assessed flavor and taste attributes while instrumental (GC-MS and LC-MS) flavor parameters were investigated as well. Although light spectra from the far-red region have been reported to substantially affect physiological and morphological parameters, to our knowledge, this effect has not been well documented under greenhouse conditions, nor to what extent these responses affect the intermediate and final yield of strawberry crops. Consequently, our experiment recommends suitable LED light regimes for greenhouse strawberry growth in the winter period.