Plant genetic resources conservation may be a potential option for the improvement of agricultural crops through modern biotechnologies, and in vitro conservation is a tool available to safeguard plant biodiversity. Ex situ conservation of plant genetic resources using the in vitro procedures is in progress in many countries. The slow growth storage (SGS) technique is a valid in vitro approach to preserve several vegetatively propagated species by controlling the growth and development of plantlets, economizing storage space and labor and reducing costs. Moreover, SGS prolongs the timing between subcultures, lowers the risk of losing germplasm through handling errors, such as contamination problems, and decreases the risk of genetic instability due to the reduction in the number of subcultures. SGS is applied by considering different factors: temperature, light or darkness conditions, medium composition, including mineral or sucrose concentrations, and the presence/absence of plant growth regulators, osmotic agents and growth inhibitors. SGS protocols for some fruit species have been well defined, others require additional research. The present review focuses on the effect of several factors that influence the SGS of in vitro shoots derived from temperate and tropical fruit species during the last ten years.

Somatic embryogenesis, as a promising biotechnological tool for many conifer trees, has never been applied for the Abies nebrodensis species. Although all the encouraging results previously obtained by the EU LIFE (European LIFE program) funded projects in over ten years, the critically endangered Sicilian fir remains alarmingly close to extinction. In this study, we reported the first protocol of somatic embryogenesis obtained from mature zygotic embryos of the Abies nebrodensis. Seeds from Abies adult trees with specific identification numbers (IN) were collected and full seeds were identified by X-ray. Different experiments were carried out for callus initiation, from both zygotic immature and mature embryos, testing different culture media. The immature embryos did not give embryogenic tissue (ET). Embryogenic callus (EC) was successfully induced from mature embryos with variable frequencies (0–40%). Schenk and Hilderbrandt (SH) was the most suitable initiation medium where the obtained callus initiation rate reached up to 40% for IN7 (first experiment). 6-benzylaminopurine (BAP) showed to be essential to induce EC (second experiment). IN8 presented the highest callus initiation rate (40%) among all tested donor trees, whereas IN13 recorded the lowest rate with 4% (third experiment). ET maturation from each singular embryo of IN7, IN8, IN10 and IN21 was successfully achieved in SH medium containing 37,83 µM abscisic acid (ABA), 8% of polyethylene glycol (PEG-4000) and 4% maltose. The encapsulation technology was assessed on the obtained ET and its proliferation was observed after encapsulation.

Abies nebrodensis (Lojac.) Mattei is an endemic species of the north-west of Sicily located in an 84 ha area in the Madonie Regional park. The relic population is limited to 30 relic adult trees and a fluctuating number of juveniles of natural regeneration. The species is defined as “Critically Endangered” in the Italian list of threatened plants and is classified as CR-D in the 2000 IUCN Red List of Threatened Species. This article reports the key action undertaken by the LIFE4FIR project aimed at preserving A. nebrodensis, and the results obtained so far in three years of activity. OpenArrays SNPs genotyping revealed a high rate of inbreeding in the natural population and that the adult trees are genetically related. Controlled cross-pollination was consequently performed to increase the genetic variability of the progeny. Outbred offspring are currently being grown in the nursery. Reforestation has been planned by using 4000 selected outbred seedlings in 10 areas within Madonie Park to create re-diffusion cores. Support and protection of the relic population have been implemented through regular phytosanitary surveys, as well as new fencing and video surveillance systems against grazing and wild herbivores. A seedbank and cryobank for the long-term germplasm conservation have been established.

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