Blue and far-red light control flowering time of woodland strawberry (Fragaria vesca) distinctively via CONSTANS (CO) and FLOWERING LOCUS T1 (FT1) in the background of sunlight mimicking radiation

Abstract

Indoor vertical farming is currently a breakthrough horticultural production system. However, for fruit bearing crops such as strawberry, a major challenge is optimizing light spectral composition to control flowering. We have shown that it is possible to stimulate flowering and fruit development with different light treatments in the day-neutral strawberry accessions Fragaria vesca ‘Yellow Wonder’ YW5AF7 and ‘Hawaii-4’. We used blue (449 nm) and far-red (740 nm) light in a background of sunlight-mimicking photosynthetic active radiation (PAR) under both long- and short-day photoperiods. Flower induction was most successful when blue light was given during the night and far-red light was given for 24 h. These light treatments overruled the photoperiodic control of flowering. Both light treatments boosted flowering, leading to a higher fruit yield, with minor effects on vegetative plant growth. We also evaluated the role of FvCO and FvFT1 using expression analysis and RNAi lines, and revealed that both blue and far-red light treatments trigger flowering in part through the conserved FvCO and FvFT1 cascade. Blue light operates through FvFT1, partially independently of FvCO, while far-red light operates independently of FvCO. Furthermore, using transcriptional reporter lines of FvFT1, we found that FvFT1 is ontogenetically and tissue-specifically regulated, being exclusively expressed in the veins of older leaves, and induced predominantly by blue and far-red light. • Blue light at night and 24 h far-red light strongly promote flowering in woodland strawberry. • These light treatments function in the background of photosynthetic active radiation. • Photoperiod dependency of flowering time control can be overruled this way. • Blue and far-red light operate via FT1, partially independent of CO. • FT1 is age- and tissue-specific, showing light induced expression in veins of old leaves.