Mertensia maritima is a commercially interesting herb with edible leaves and flowers, characterized by oyster flavor and taste. Plant propagation and traditional cultivation are challenging for this species. Therefore, the main purpose of the present study was to establish successful protocols aimed at ensuring oyster plant shoot propagation, rooting and in vivo acclimatization. Both micropropagation and rooting were tested, comparing the traditional in vitro solid substrate in jar vs. the liquid culture in a temporary immersion system (TIS) bioreactor (Plantform™). A Murashige and Skoog (MS) medium added with 4-μM thidiazuron (TDZ) and 1-μM α-naphthaleneacetic acid (NAA) was employed for micropropagation, while a half-strength MS medium supplemented with 4-μM indole−3-butyric acid (IBA) was used for rooting. Different acclimatization conditions in the greenhouse or in growth chamber were tested. Morphometric and microscopical analyses were performed on the oyster plant leaves at the propagation, rooting and acclimatization stages both in a jar and in a TIS. Micropropagation in a TIS allowed to obtain large shoots, while a great number of shoots was observed in the jar. M. maritima shoots rooted in TIS produced more developed roots, leaves with more developed waxy glands and well-formed stomata; moreover, the plants coming from the TIS showed the best acclimatization performances.

Ocimum basilicum (sweet basil) is an economically important aromatic herb; in Italy, approximately 1000 ha of “Genovese-type” basil are grown annually in greenhouses and open fields and are subjected to Downy Mildew (DM) disease, caused by Peronospora belbahrii, leading to huge crop losses. Mutation of the Susceptibility (S) gene DMR6 (Downy Mildew Resistant 6) has been proven to confer a broad-spectrum resistance to DM. In this work, an effective Genome Editing (GE) approach mediated by CRISPR/Cas9 in O. basilicum ‘Italiko’, the élite cultivar used to produce “Pesto Genovese D.O.P”, was developed. A highly efficient genetic transformation method mediated by A. tumefaciens has been optimized from cotyledonary nodes, obtaining 82.2% of regenerated shoots, 84.6% of which resulted in Cas9+ plants. Eleven T0 lines presented different type of mutations in ObDMR6; 60% were indel frameshift mutations with knock-out of ObDMR6 of ‘FT Italiko’. Analysis of six T1 transgene-free seedlings revealed that the mutations of T0 plants were inherited and segregated. Based on infection trials conducted on T0 plants, clone 22B showed a very low percentage of disease incidence after 14 days post infection. The aromatic profile of all in vitro edited plants was also reported; all of them showed oxygenated monoterpenes as the major fraction.

Sweet basil (Ocimum basilicum L.; Fam. Lamiaceae) is an annual herbaceous plant with a high economic value used in folk medicine, pharmacology, and food production. In Italy, most of the varieties are used to produce the famous “pesto” sauce; however, almost all of them are susceptible to basil downy mildew (BDM) disease, strongly decreasing the growth of the fresh leaves and the survival of the whole plant. Nowadays, CRISPR/Cas9 technology is recognized to be a prominent way to enhance basil genetic breeding. In this work, we present an optimized protocol for in vitro direct regeneration of an elite cultivar, which is the major limiting factor for the transformation of O. basilicum. Regeneration has been obtained from different explants (leaves, cotyledons, cotyledonary nodes); the highest frequency has been obtained from cotyledonary nodes of seedlings germinated on MS medium containing TDZ. This protocol may be used for biotechnological applications as genome editing techniques to obtain basil-downy-mildew-disease-resistant clones.

Agastache aurantiaca ‘Sunset Yellow’ and A. mexicana ‘Sangria’ are aromatic plants with edible flowers characterized with good flavors, nutritional values and pleasant aromas. The aim of this study was to establish a successful protocol to ensure fast shoot propagation, rooting and in vivo acclimatization to obtain many vigorous plants for edible flower production. Micropropagation was tested with an agarized Murashige and Skoog (MS) medium enriched with different 6-benzylamino purine (BAP) levels. In vitro rooting trials were carried out using a half-strength MS medium comparing the traditional jar method with an agarized medium and the temporary immersion system (TIS) bioreactor with a liquid medium. After acclimatization in a greenhouse, the survival of plants and their development were recorded. Microscopical analyses were performed on both in-jar and in-TIS leaves at rooting stages and compared with in vivo leaves. In both species, the greatest number of new shoots was noted at 2.22 µM and 3.33 µM of BAP. In TIS, rooting started earlier, resulting in larger plants with more roots and longer roots than in the jar substrate. Any anatomical difference was observed in leaves collected from the jar and TIS during the rooting stage. The best acclimatization performances were recorded in plants coming from the TIS bioreactor.

The Nemo’s Garden^® project is an alternative production system for areas with scarce cultivable land but significant presence of water; thus, it is an interesting intervention to address the climate crisis. This work aimed to evaluate the micromorphological, biochemical, and phytochemical characteristics of Stevia rebaudiana (Bertoni) Bertoni grown underwater compared to the terrestrial specimens. The micromorphological analyses, performed on the leaves using light microscopy, fluorescence microscopy, and scanning electron microscopy, evidenced a general uniformity of the trichome morphotype and distribution pattern. The histochemical investigation indicated the simultaneous presence of terpenes and polyphenols in the trichome secreted material from the underwater samples and a prevailing polyphenolic content in the terrestrial specimens; this was also confirmed by biochemical analyses (26.6 mg GAE/g DW). The characterization of non-volatile components, performed using HPLC–MS, showed similar chemical profiles in all the samples, which were characterized by phenolic compounds and steviol glycosides. The volatile compounds, evaluated using HS-SPME coupled with GC–MS, showed sesquiterpene hydrocarbons as the main class in all the analyzed samples (80.1–93.9%). However, the control plants were characterized by a higher content of monoterpene hydrocarbons (12.1%). The underwater biosphere environment did not alter S. rebaudiana micro-morphological characters, although slight qualitative changes were evidenced for the compounds produced as a response to the growth conditions.

Ornamental plants constitute an important sector of the agricultural market, with global relevance. The impacts of climate change also affect flowering plants, increasing susceptibility to stress conditions. The most common effects are related to germination capacity and uniformity, which can indirectly compromise aesthetic value. Seed priming represents a promising environmentally friendly strategy to improve germination performance and stress tolerance in ornamental plants. This review gives an overview of the most recent advances in priming applied to ornamental species, highlighting the physiological, biochemical, and molecular impacts of the technique. Priming approaches can differ (e.g., hydro-, osmotic, hormonal, nano-based), with the common aim of enhancing germination efficiency, seed vigor, and promoting greater uniformity and quality of plantlets under stress conditions. Up to now, a bottleneck in the use of this promising tool has been represented by different responses related to species and protocol standardization. Molecular evaluation is required to monitor the long-term effectiveness of priming. The use of priming represents a sustainable and low-cost tool to enhance the adaptability of ornamental species in stress conditions, supporting the transition to new sustainable solutions for the future of ornamental plant production.