Optimizing Adventitious Shoot Regeneration in Peach Cultivar and Hybrid Rootstock Genotypes by LED Light Spectrum Modulation

Adventitious shoot regeneration is an essential prerequisite for the application of biotechnological tools such as CRISPR-Cas in woody fruit crops. Nonetheless, many Prunus species exhibit strong recalcitrance to in vitro regeneration. Light quality has emerged as an important environmental factor influencing morphogenic responses under in vitro conditions. In this study, the effect of different LED light spectra on adventitious shoot regeneration was evaluated in three peach-related genotypes: the commercial peach cultivar ‘Siroco 5’ (Prunus persica L.) and the hybrid rootstocks ‘GF677’ and ‘Garnem’ (P. persica × P. dulcis). Callus explants derived from the basal region of in vitro proliferation cultures were exposed for 30 days to five LED light treatments: white (control), blue, red + far-red, mixed (red + far-red + blue), and sequential LED light. Regeneration efficiency was assessed through the frequency of organogenic callus formation (FOC), the number of regenerated shoots per explant, the organogenic rate, and the fresh weight of the regenerated explants. While FOC was consistently high across genotypes and light treatments, shoot regeneration was significantly influenced by both genotype and light spectrum. The hybrid rootstocks exhibited a higher regeneration capacity than the commercial cultivar under most conditions. Red + far-red LED light promoted the highest regeneration efficiency across all of the genotypes, particularly enhancing shoot regeneration and fresh weight in ‘Siroco 5’. These results demonstrate that LED light spectrum modulation, especially red + far-red, is an effective strategy to optimize adventitious shoot regeneration in peach cultivar and hybrid rootstock genotypes, providing a robust basis for future applications in micropropagation and genetic improvement programs.