Duboisia is an Australian native woody species of the Solanaceae family, a crucial source of alkaloids, and is naturally extracted for pharmaceuticals. The alkaloid content of the four naturally occurring species of Duboisia, i.e., Duboisia myoporoides R. Br., Duboisia leichhardtii F. Muell., Duboisia hopwoodii F. Muell. and Duboisia arenitensis, is not conducive for large-scale commercial extraction. High-value hybrids between D. myoporoides R. Br. and D. leichhardtii F. Muell. have become the commercial crop for the industry. Propagation of these hybrids is key for progression of this industry, especially for the establishment and expansion of plantations and to replenish old plantations. Commercial propagation of Duboisia completely depends on cutting propagation to ensure true-to-type propagules. Cutting propagation of this species is associated with several challenges and has been a hurdle for industry expansion for many years. Micropropagation can be an efficient and sustainable alternative for Duboisia clonal propagation and is a faster and cleaner propagation avenue for elite propagules. This review compiles the research attempts made in the space of Duboisia micropropagation and provides an update on recent advancements to understand the technical capacity, progress and challenges towards a commercial micropropagation platform.

The Duboisia species, a group of plants native to Australia, have been historically valued for their pharmacological properties and have played a significant role in traditional medicine and pharmaceutical research. Persistent efforts are underway to enhance the efficacy of the active ingredient scopolamine, employing both conventional breeding methods and advanced biotechnology tools. The primary objective of this research was to establish a highly efficient method for isolating mesophyll protoplasts and facilitating their regeneration, thereby laying a robust foundation for the application of various advanced plant biotechnology tools in the pursuit of genetic enhancement. The mesophyll protoplast isolation process was developed for hybrid D. myoporoides × D. hopwoodii with careful optimisation of the following parameters: leaf strip size; incubation conditions; physical treatment; and enzyme concentration. The optimal parameters were combined in each individual step; the best enzyme concentration was determined to be 2% (w/v) cellulysin and 0.5% (w/v) macerase. Protoplast yield was found to be greatly affected by the enzyme concentrations. The isolated protoplasts were cultured at a density of 0.5 × 10⁵ to best sustain the highest cell division (33.2%) and a microcalli induction frequency of 17.9%. After 40 days of culture in a modified KM8P medium at 25 °C in darkness, visible microcalli were transferred to a solidified Murashige and Skoog (MS) medium with 1 mg L⁻¹ 2,4-dichlorophenoxyacetic acid (2,4-D) for callus induction under a 16 h photoperiod. After 30 days of culture, compact organogenic calli were transferred into a solid MS medium with 6-benzylaminopurine (BA) alone or thidiazuron (TDZ) alone or in combination with BA or naphthalene acetic acid (NAA) for shoot regeneration. The maximum shoot regeneration frequency (63.3%) was observed in the medium with 1.5 mg L⁻¹ TDZ alone. For the first time, a reliable protoplast isolation and regeneration system from mesophyll cells was established for Duboisia with high protoplast viability, successful microcalli formation, and intact plant regeneration. This innovation will significantly contribute towards the genetic enhancement of the Duboisia species.

Duboisia is an Australian native, commercially valuable for tropane alkaloid extraction. Clonal propagation of elite selections is essential to establish highly productive plantations. The current propagation system using stem cuttings is proven to be inefficient, prompting the industry to seek a more efficient and effective propagation tool. Tissue culture is a cost-effective alternative for mass propagation of true-to-type plants, particularly ideal for propagating elite Duboisia selections. In this context, attempts were made to develop a commercially viable high throughput micropropagation system for three Duboisia species: Duboisia myoporoides, Duboisia leichhradtii and Duboisia hopwoodii. Various nutrient media, hormone combinations and incubating conditions were tested to optimise each stage of the micropropagation pipeline. The findings revealed that the tissue culture media composition and hormone requirements are species-specific. With the optimised conditions, an efficient tissue culture system was developed, achieving successful meristem induction and multiplication. Species-specific rooting protocol optimisation resulted in 100% rooting for D. myoporoides and D. leichhardtii, and 70% rooting for D. hopwoodii. Furthermore, an optimised acclimatisation protocol supported 100% survival of D. myoporoides and D. leichhardtii and 80% of D. hopwoodii plantlets. This study, for the first time, demonstrated the capacity of successful meristem culture of three Duboisia species, establishing the foundation for high throughput micropropagation of Duboisia species.

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