Supplemental Light-emitting Diode Effects on the Growth, Fruit Quality, and Yield of Two Greenhouse-grown Strawberry (Fragaria ×ananassa) Cultivars

Abstract

Recent interest in off-season greenhouse-grown food crops, in combination with supplemental (top) lighting (SL), has created opportunities for local production of high-value fruit crops such as strawberries (Fragaria ×ananassa). Light-emitting diodes (LEDs) as SL can be tailored to a specific quality of radiation (i.e., wavelengths) to promote increased production and quality of greenhouse-grown crops. The objectives of this study were to evaluate the effects of three LED light bars on off-season controlled environmental agriculture (CEA) production of 2-day neutral strawberry cultivars: Albion and San Andreas. LED effects on overall vegetative biomass (e.g., stolon production, crown number, and leaf area), marketable fruit yield, and fruit quality [e.g., individual fruit weight and soluble solids content (SSC)] were measured during decreasing daylengths from Oct. to Dec. 2017 (Expt. 1) and increasing daylengths of Jan. to Apr. 2018 (Expt. 2). We hypothesized that the addition of SL via three LED treatments would increase measured parameters. Specifically, it was expected that the LED bars [high blue (HB) and low blue (LB)] with greater intensities of blue and red light would produce greater yields and also increase SSC of the berries. The hypotheses were tested by evaluating three LED light top bars [white far-red (WFR; 440–450 nm), HB, and LB], with wavelength peaks of blue (450 nm) and red (665 nm) light, but differing photosynthetic photon flux densities (PPFDs). Results from these experiments showed that individual strawberry fruit size and SSC were increased with the use of HB and LB LEDs during the shortening days of Expt. 1. Increased leaf area and crown number were also affected positively within all LED treatments (WFR, LB, HB) for ‘San Andreas’. Relative to Expt. 1, the lengthening days of Expt. 2 elicited more limited fruit responses, although increased stolon production within all treatments was reported. In addition, differences between cultivars in leaf area and SSC were observed with ‘San Andreas’ growing larger leaves and ‘Albion’ berries having a greater SSC. Individual fruit weight of both cultivars responded similarly, with increased fruit size in LB and HB, specifically within both Expt. 1 and Expt. 2. Our studies indicate that the addition of SL, in the form of LB and HB improved overall strawberry fruit quality and plant growth during shortening daylengths and under greenhouse CEA conditions.