Several olive cultivars, characterized by high-quality olive oil show agronomical issues such as excessive vigor, high susceptibility to biotic and abiotic stresses, and low propagation ability. They are strong candidates for breeding based on new technologies to improve their performance in a short period of time. For this reason, the first step is developing efficient somatic embryogenesis (SE) protocols. Somatic embryogenesis in olive is highly genotype-dependent for both adult tissues and mature embryos as initial explants, requiring the development of specific protocols for each genotype. Trials using cotyledons and radicles as initial explants, isolated from ripe seeds from the Portuguese olive cv. ‘Galega vulgar’, gave more than 95% calli development. Radicles proved to be the most responsive tissue for SE induction, with an average of 2 embryos per callus after callus transfer to expression medium, and 14 embryos per callus after subculture on the olive cyclic embryogenesis medium (ECO). Embryogenic competence could be recovered after several subcultures on ECO medium that maintained cyclic embryogenesis for an indeterminate period of time. Embryo conversion and plant acclimatization were also attained with high success rates. Media management for cyclic embryogenesis maintenance is of general importance for SE protocols in any olive genotype. Somatic embryogenesis was thus attained for the first time in embryo-derived explants of cv. ‘Galega vulgar’.

Several physiological and yield parameters were evaluated in lettuce plants, cv. ‘Trocadero’, while growing at four different photosynthetic photon flux (PPF) (70, 120, 250 and 400 ± 10 µmol m-2 s-1), under four light spectra, white (W), red (R) and blue (B) Light-Emitting Diode (LED) lamps and cool white fluorescent tubes (FL). Yield parameters were also evaluated on spinach, turnip and radish, growing under identical light spectra but using a single PPF (340 ± 10 µmol m-2 s-1). Lettuce development was impaired at PPFs below 250 µmol m-2 s-1 for all tested spectra. At higher PPFs (250 and 400 ± 10 µmol m-2 s-1), for the two broad spectra tested (W LEDs and FL light), no significant differences were registered on all physiological and yield parameters evaluated. On all situations W LEDs performed, at least, as good as the FL light, indicating that actual W LEDs can efficiently replace traditional light sources, with all the inherent benefits, which include significant lower power consumption. For all species, narrow light spectra (R and B LEDs) proved not being able to provide normal plant development. Plants under R LEDs, although presenting, in some situations, a fresh weight higher than those achieved with the broad light spectra, always led to abnormal plant morphology, characterized by expanded petioles and leaf curling. B LEDs, in spite of promoting plant growth with normal morphology, frequently led to a lower number of leaves and consequently to a lower fresh weight.

In vitro micropropagation is already a current multiplication tool for walnut self-rooted cultivars and rootstocks, but walnut grafting is still performed in the field or in greenhouses, mainly using seedlings as rootstocks. The present work describes a new approach to obtain clonal walnut-grafted plants, involving in vitro shoot production of ‘Paradox’ (Juglans hindsi × Juglans regia) cl. ’Vlach’, to be used as rootstock, and J. regia cv. ‘Chandler’, to be used as scion. After completing the in vitro multiplication phase and a seven-day root induction treatment, ‘Vlach’ explants are transferred to ex vitro conditions for root expression while being simultaneously grafted using the in vitro produced ‘Chandler’ scions. The importance of the presence of leaves on both the scion and the rootstock for the success rate of the technique was evaluated. Under optimal conditions, average success rates of 82% for rootstock rooting, 72% for micrografting survival, and 84% for grafted plant acclimatization were achieved. This rooting/grafting combination technique seems able to compete with the traditional techniques of nursery grafting, allowing obtaining high-quality walnut-grafted plants independently of the external weather conditions in a significantly shorter time.

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