Optimizing the light environment for indoor strawberry production is critical for ensuring high productivity and fruit quality. Short-day (SD) strawberries require SD conditions for flower induction. However, SD can also cause semi-dormancy symptoms that inhibit strawberry plant growth and production. Current strategies to address this challenge in SD strawberry production is extension of photoperiod to prevent semi-dormancy. This preliminary study investigated the effect of photoperiod adjustment and light quality modification by analyzing two SD strawberry cultivars ‘Earliglow’ and ‘Nyohou’ under three photoperiod treatments (SD, LD, or alternating SD/LD) with or without supplemental far-red (FR) treatments (56 % FR over total photon flux density, 400-750 nm). Plants under continuous SD conditions exhibited a typical semi-dormancy like morphology with shorter petioles and peduncles. Supplemental FR treatment significantly extended petiole and peduncle length, regardless of daylength. Strawberry total yield, percent marketable yield, and total number of fruit were improved in plants with supplemental FR treatment. Supplemental FR light treatment also increased soluble solid concentration (SSC, brix %) and SSC-to-TA ratio regardless of cultivar. No significant differences in leaf net photosynthetic rates were observed among photoperiod or FR treatments. The increase in productivity and fruit SSC was partly attributed to improved plant morphology under supplemental FR light, which enhanced photoassimilates allocation to fruit. Addition of FR light seems to be beneficial in indoor production of SD-type strawberry cultivars for preventing semi-dormancy and enhancing yield and fruit quality.
