Cannabis sativa has been cultivated for thousands of years across different continents.  However, scientists are only beginning to scratch the surface with cannabis research due to the protracted era of prohibition.
In the last few years, progressive advances such as the legalization of hemp have sparked a renewed interest in cannabis research. However, not many researchers have looked into Cannabis tissue culture. A 2021 review of the scientific literature provides an in-depth look at Cannabis tissue culture while paying keen attention to current challenges facing researchers citing recent developments and giving directions for the future. 
The many years of prohibition meant that the decades of underground breeding and hybridization now lack any formal records. This has made it difficult for researchers to establish cultivar pedigrees. The consumer is even more thrown off by the chemical unpredictability of cannabis plants.
Modern cannabis hybridization has created the need for a better understanding of Cannabis tissue culture which provides the framework for micropropagation as well as New Plant Breeding Technologies (NPBTs).
Due to rapid hybridization, Cannabis has been classified as a polymorphic and monospecific species. Scientists have discovered great diversity in the biochemical and morphological characteristics of cannabis leading them to preemptively suggest a polyspecific genus.
Cannabis, being an adaptable crop, can be cultivated in a range of settings from rudimentary to highly sophisticated commercial greenhouses. Micropropagation is a technique that uses tissue culture to propagate cannabis in a micro-controlled environment using aseptic techniques. The aseptic medium eliminates abiotic pressures, leading to disease-free plants.
Challenges Affecting Micropropagation
The main challenge affecting micropropagation is specificity at the species and genotype level that causes variations at each stage of propagation. The high specificity of the tissues and genotype affects the regeneration responses of the plant. Regenerative ability will vary from one species to another.
A different challenge is the development of a single shoot leading to poor survival rates. Floral reversion is a technique that can be used to boost the multiplication rate. This involves a migration out of the flowering stage back to the vegetative stage. De novo systems of regeneration can also increase tissues for micropropagation.
Other challenges involving in vitro cannabis tissue culture include:
- Lack of reproducibility
- Recalcitrance to regeneration
- The ambiguity of reported results
Micropropagation produces plants that are structurally and biochemically similar to the parent and also genetically stable. There’s a need to optimize both macro- and micronutrients to achieve success with micropropagation. 
While micropropagation is nonlinear and complex, new advances can help to sort out challenges that affect tissue culture. This includes advances in machine learning that can be employed to optimize shoot regeneration, androgenesis, and other techniques that support in vitro tissue cultures. Nanoparticle technology (including quantum dots, graphite, titanium dioxide, and silver) is also useful in providing a comprehensive view of micropropagation and provides an opportunity to tackle persistent recalcitrance as well as diminished replicability that frustrates in vitro cannabis tissue culture studies.  These nanoparticles have been hypothesized to provide beneficial outcomes due to their delaying deterioration due to age.
Ultimately, the study authors concluded that “innovative new approaches to Cannabis micropropagation are required if developments in Cannabis tissue culture and plant biotechnologies are to keep pace with the needs of the producers and consumers in this burgeoning industry.”
References Chouvy P. Les frontières, fronts inefficaces de la lutte contre le trafic international de drogue. L’Espace Politique. 2020. [journal impact factor = 5.753; times cited = 5]
 Monthony AS, Page SR, Hesami M, & Jones A. The Past, Present and Future of Cannabis sativa Tissue Culture. Plants (Basel, Switzerland). 2021;10(1):185. [journal impact factor = 3.935; times cited = 14].