Somatic Mutation Accumulations in Micropropagated Cannabis Are Proportional to the Number of Subcultures

Advancements in micropropagation techniques have made it easier to produce large numbers of cannabis clones, but these methods may also introduce genetic instability over successive generations. This instability often manifests as somaclonal variation, characterized by the progressive accumulation of genetic mutations or epigenetic alterations with each subculture. In this study, we examined how mutations accumulate in cannabis clones subjected to 6-11 subcultures. Using genotyping-by-sequencing, we identified 9405 polymorphic variants across 70 clones. The analysis revealed a correlation between the number of subcultures and the frequency of these mutations, revealing that genetic changes accumulate over successive subcultures despite clones sharing the same chronological age. Furthermore, we evaluated the functional impacts of accumulated mutations, with particular attention to implications on gene function and overall plant health. While rare, 14 high-impact variants were identified in genes that are important for plant development. Notably, six variants were also found in genes related to cannabinoid and terpene synthesis pathways, potentially affecting the plant's biochemical composition. These findings highlight the need for genetic assessments in micropropagation protocols, impacting plant breeding and conservation. Understanding genetic variations in clonally propagated plants optimizes practices for stability. Crucial for cannabis and horticultural plants, it emphasizes techniques to prevent genetic decay and ensure viability.

In vitro conservation and cryopreservation of ornamental plants

Today, the conservation of ornamental germplasm can take advantage of innovative techniques which allow preservation in vitro (slow growth storage) or in liquid nitrogen (cryopreservation) of plant material. Slow growth storage refers to the techniques enabling the in vitro conservation of shoot cultures in aseptic conditions by reducing markedly the frequency of periodic subculturing, without affecting the viability and regrowth of shoot cultures. Cryopreservation refers to the storage of explants from tissue culture at ultra-low temperature (-196 degrees C). At such temperature, all the biological reactions within the cells are hampered, hence the technique makes available the storage of plant material for theoretically unlimited periods of time. An exhaustive review of papers dealing with the slow growth storage and the cryopreservation of ornamental species is reported here. Step-by-step protocols for the slow growth storage of rose germplasm, the production of synthetic seeds for the in vitro conservation of ornamentals, and the cryopreservation of Chrysanthemum morifolium are included.