By Dr. Daniela Vergara
Cloning Cannabis sativa plants through cuttings is common in the industry to maintain consistency. Now tissue culture is also becoming commonly used. But over time, growers have noticed that cloned plants may lose quality.
The aroma, strength, and even the size of the plants can change. Why does this happen?
According to some research, it could be due to genetic mutations and epigenetic changes that build up as the plant is cloned again and again or simply ages.
Mutations Increase
Somatic mutations, which are genetic changes that happen after a plant starts growing, increase in clones that were grown in tissue culture (Adamek et al. 2024). This study used GBS (Genotyping by sequencing) a sequencing technique that we talked about in a previous post.
According to the findings, C. sativa clones start building up mutations in their DNA as cloning continued.
As plants were grown through more and more subcultures, the number of mutations increased by about 34%. There was a strong relationship between how many times the plants were subcultured and how many mutations they had. The regression coefficient was over 0.92, which means the more subcultures there were, the more mutations showed up.
As subcultures increased, the number of places where these changes were found also increased, but the overall diversity in the DNA went down.
Most mutations didn’t do much (91.5% were classified as “modifiers”), but some were more serious and could show changes in important genes cush as those related to cannabinoid and terpene production.
This beautiful study shows that subculturing causes real genetic changes over time, and even though the clones may look the same, their DNA is quietly changing in ways that can affect traits important to growers and consumers (Adamek et al. 2024).
Genetic Diversity within one plant
This same group of people also explored something called the Genetic Mosaicism Hypothesis. This idea suggests that a single C. sativa plant can become genetically different in its different parts as it grows (Adamek et al. 2022).
To do this, they sequenced DNA from different parts from the top, middle and bottom of a mother C. sativa plant.
They found that each part of the plant had different mutations, and the top of the plant had the most, with 34% of its mutations being completely unique.
This shows that a C. sativa plant is not genetically uniform. Over time, and especially in tall or pruned plants, parts of the plant may evolve their own set of mutations.
This is important for growers because the cuttings taken from the top of the plant could have different traits than those from the bottom even though they came from the same mother plant.
Epigenetics: Changes Without DNA Mutations
While mutations are permanent changes in DNA, epigenetics involves changes in how genes are turned on or off but without changing the DNA. Epi means above, so these changes are not in the DNA per se, but in molecules above the DNA. However, both genetic and epigenetic mutations may be inherited from parents to offspring and can influence the plant’s phenotype (physical characteristics).
Epigenetic mechanisms may affect clones in the following ways:
Histone Modifications
Histones are proteins that DNA wraps around and are very important to form chromosomes. Chemical tags (like methyl or acetyl groups) can be added or removed from histones, changing how tightly DNA is wrapped and whether genes are turned on or off.
DNA Methylation
This involves adding a methyl group to parts of the DNA (usually cytosine bases), which can silence genes. In other crops, DNA methylation has been linked to changes in growth and defense.
ATP-Dependent Nucleosome Remodeling
This process moves or reshapes parts of the DNA structure so that certain genes become more or less accessible for use. It plays a role in how plants grow and how they produce compounds like THC and CBD.
Small RNAs
We haven’t yet talked about RNA so let me do a short introduction: RNA is a molecule that helps cells use the instructions in DNA. It carries the message from DNA to make proteins, which do important jobs in the body. RNA can also help control which genes are turned on or off.
Small RNAs are These are tiny RNA molecules that don’t code for proteins but can control how other genes are used. They can even guide DNA methylation.
Together, these epigenetic tools help the plant respond to its environment—but in clones, these changes can accumulate over time, creating differences in plant performance even if the DNA hasn’t changed (Hesami and Jones 2023).
So, if you are a grower…
These findings explain why some C. sativa growers notice their clones aren’t as strong, flavorful, or productive after many cycles. Even if the clones came from a great parent, mutations in the DNA (genome) and in the epigenome can affect the phenotype and overall quality over time.
Genetic and epigenetic changes in C. sativa clones are real and measurable. Keep in mind that micropropagation and repeated subculturing can increase the chance of genetic changes in plants. Older mother plants might even have different genetics in different parts. Even without changes to the DNA, epigenetics may affect how genes work, which can change important traits that we desire in the plants. To keep plant quality high, it helps to limit cuttings and subcultures, to rotate mother plants, and to reduce stress.
I hope you liked this post, I learned a lot while reading the papers that I’m citing, so thank you!
References
Adamek, K., A. M. P. Jones, and D. Torkamaneh. 2022. Accumulation of somatic mutations leads to genetic mosaicism in cannabis. The Plant Genome 15:e20169.
Adamek, K., A. M. P. Jones, and D. Torkamaneh. 2024. Somatic Mutation Accumulations in Micropropagated Cannabis Are Proportional to the Number of Subcultures. Plants 13:1910.
Hesami, M. and A. M. P. Jones. 2023. Potential roles of epigenetic memory on the quality of clonal cannabis plants: Content and profile of secondary metabolites. Pp. 91-104. Medicinal Usage of Cannabis and Cannabinoids. Elsevier.
