Integration of Green and Far-Red Light with Red-Blue Light Enhances Shoot Multiplication in Micropropagated Strawberry

Light spectral composition critically regulates plant morphogenesis and molecular adaptation in controlled environments. This study investigated the synergistic effects of three light spectra, red-blue (RB, 7:3), red-blue-green (RGB, 7:3:1), and red-blue-far-red (RBFR, 7:3:1), on multiplication, morphogenesis, physiological traits, and transcriptomic dynamics in tissue-cultured strawberry (Fragaria × ananassa cv. ‘Benihoppe’). After 28 days of cultivation under controlled conditions (25 °C/22 °C day/night, 50 μmol·m−2·s−1 PPFD), RBFR and RGB treatments significantly enhanced shoot multiplication (38.8% and 24.2%, respectively), plant height, and callus biomass compared to RB light. RGB elevated chlorophyll a and b by 1.8- and 1.6-fold, respectively, while RBFR increased soluble protein content by 16%. Transcriptome analysis identified 144 and 376 differentially expressed genes (DEGs) under RGB and RBFR, respectively, enriched in pathways linked to circadian rhythm, auxin transport, and photosynthesis. Far-red light upregulated light signaling and photomorphogenesis genes, whereas green light enhanced chlorophyll biosynthesis while suppressing stress-responsive genes. These findings elucidate the spectral-specific regulatory mechanisms underlying strawberry micropropagation and provide a framework for optimizing multispectral LED systems in controlled-environment horticulture.