The present study aims to generalize cultivar-specific tree phenology responses to winter and spring temperatures and assess the effectiveness of the Tabuenca test and various chill and heat accumulation models in predicting bloom dates for a wide range of climatic conditions and years. To this end, we estimated the dates of rest completion and blooming and correlated them with observed bloom dates for 14 peach and nectarine cultivars that were evaluated in 11 locations across Europe (Greece, France, Italy, Romania and Spain), within the EUFRIN cultivar testing trial network. Chill accumulation varied considerably among the studied sites, ranging from 45 Chill Portions (CP) in Murcia-Torre Pacheco (Spain) to 97–98 CP in Cuneo (Italy) and Bucharest (Romania). Rest completion occurred latest or was not achieved at all for some cultivars in the southern sites in Murcia. Dormancy release happened earliest in Bucharest and Cuneo, sites where heat accumulation had a strong influence on the regulation of bloom time. Blooming occurred earliest in the moderately cold regions of Lleida (Spain) and Bellegarde (France), and 7–11 days later in the warmer locations of Rome (Italy) and Naoussa (Greece), suggesting that bloom timing is strongly influenced by delayed rest completion in these locations. The Dynamic Model resulted in both more homogeneous chill accumulation across years and better predictions of bloom dates, compared with the Utah, Positive Utah and Chilling Hours models. Prediction of bloom dates was less successful for low-chill cultivars than for medium- and high-chill cultivars. Further climatic and experimental data are needed to make estimates of the climatic needs of peach cultivars more robust and to generate reliable advice for enhancing the resilience of peach production under varying and changing climatic conditions.

Light influence on shoot regeneration in Prunus salicina is a complex interaction that has been studied for the first time. Japanese plum plants were regenerated from calli and seeds of the scion cultivar ‘Victoria’. The effect of four different light spectra (white, blue, red, and mixed), along with three 6-benzyladenine (BA) concentrations (1, 1.5, and 2 mg L⁻¹), was studied in these two sources of explants. Organogenic calli were derived from the base of stem explants of the scion cultivar ‘Victoria’, whereas cotyledons and embryogenic axis slices were used as seed explants. Calli cultured with 2 mg L⁻¹ of BA and mixed light or 2.5 mg L⁻¹ of BA and control light showed the highest regeneration rates, with no significant differences compared to other treatments. Seed explants exposed to 2.5 mg L⁻¹ of BA and red light exhibited significantly higher organogenesis. In comparison, those in 1.5 mg L⁻¹ of BA with blue light or 2.5 mg L⁻¹ of BA with mixed/control light showed no regeneration. BA concentration did not have a significant effect in the induction of somatic shoots from any explant source. In contrast, a strong interaction between light and BA was noticed. This work presents a protocol that can be applied in transformation and editing research as light spectrum studies continue to advance.

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.

Plants have a remarkable ability to regenerate tissues and organs from single cells, a property that underpins in vitro protoplast regeneration. Efficient protoplast-to-plant regeneration remains a major bottleneck for genome engineering in many crop species, including broccoli (Brassica oleracea var. italica). In this study, we established and optimized a regeneration system for broccoli cv. Claremont by evaluating enzyme composition, light quality, and culture media at successive stages of development. Among the tested enzyme mixtures, 1.5% Cellulase R-10 combined with 0.4% Macerozyme R-10 yielded the highest protoplast viability and recovery. Alginate-embedded protoplasts were cultured under control (dark), blue, and red + far-red LED illumination. Red + far-red treatment significantly enhanced microcolony formation, plating efficiency, and shoot regeneration compared with blue light, whereas blue illumination consistently reduced regenerative performance. The inclusion of activated charcoal in the regeneration medium further increased shoot production. The generalized linear model analyses identified light quality as a significant predictor of both shoot number and regeneration. To our knowledge, this study provides one of the first demonstrations of LED-assisted enhancement of protoplast regeneration in broccoli. The optimized protocol enables whole-plant recovery within approximately 5 months and offers a practical platform for CRISPR-based genome editing and advanced breeding applications in B. oleracea.