Effect of Different Media and Plant Hormone Concentrations on Callus Induction and Regeneration of Red Squill (Squilla maura) and Peruvian Squill (Oncostema peruviana)

Two bulbous plant species, Squilla maura and Oncostema peruviana (Asparagaceae), show particularly interesting ornamental and medicinal characteristics. Micropropagation could be a promising alternative method to accelerate their naturally slow spreading pattern. This study focused on the effects of different growth regulators and culture media on callus induction and shoot regeneration, from which an effective protocol was established. Leaf explants were cultured on Murashige and Skoog (MS), MS/2, or B5 medium, containing one auxin—1-Naphthaleneacetic acid (NAA), 2,4-Dichlorophenoxyacetic acid (2.4-D), or 3-indolebutyric acid (IBA)—combined with the cytokinin 6-Benzylaminopurine (BAP), at various concentrations. All treatments resulted in callogenesis rates between 65–100% for both species. These treatments led to direct bulbil regeneration. Among the treatments, the B5 medium with 1 mgL−1 BAP and 1 mgL−1 2,4-D gave the highest regeneration rate (89.2%) for O. peruviana, while the ½MS medium with 0.5 mgL−1 BAP and 0.5 mgL−1 NAA showed the highest regeneration rate (85.5%) for S. maura. The highest mean number of bulils per explant was 7.44 for O. peruviana on the MS medium (0.5 mgL−1 BAP and 2 mgL−1 IBA), and 9.5 for S. maura on the MS medium (1 mgL−1 BAP and 0.5 mgL−1 NAA). The regenerated bulbils were transferred for multiplication to the MS medium with a hormone combination (2 mgL−1 BAP and 0.2 mgL−1 NAA) which increased the multiplication rate compared to the callus induction me dium, with a highest recorded multiplication rate of 177 (O. peruviana) and 104.33 (S. maura). The propagation stage achieved the highest number of bulbils/explant after a second subculture for the two species. An efficient micropropagation protocol was established for S. maura, which answers our main objective, and it would contribute to their conservation and sustainable use in ornamental and medicinal applications.