The genetic makeup of an organism that determines its possible characteristics. In cannabis, this includes the plant’s color, height, resistance to disease, and general ability to produce resins. The genotype of a cannabis plant is the key to understanding the genetic potential of the cultivar and how environmental conditions may influence its growth and physical appearance.
“A plant’s genotype is not the same as its phenotype.”
“Those seeds have similar genotypes because they were harvested from the same mother plant.”
More About Genotypes
Before a plant even begins to grow, its seed contains all the genetic information that will determine its spectrum of possible visual, physical, and growth characteristics. A cannabis cultivar’s full set of genetic traits within its DNA is called a genome. Though not all DNA influences the growth traits of the plant, all the DNA that translates into proteins will make up a plant’s genome.
The genotype represents a spectrum of possibilities that a given plant will exhibit. Two different cannabis plants of the same cultivar, for example, won’t have completely identical traits but share similar genotypes inherited from their mutual mother plant. Other than clones, which contain exact copies of the original genome, no two plants have the exact same genotype.
The Difference Between Genotypes and Phenotypes
How do plants with the same genotype display different physical characteristics? The answer lies in the difference between a genotype and a phenotype, which can be summed up in this simple equation: genotype + environmental interaction = phenotype.
A cannabis phenotype is comprised of the visible characteristics or traits of a plant, which determine where a plant will end up within its spectrum of genetic traits, as determined by the genome. The color and shape of a plant’s leaves, the density of its trichomes, the yield and structure of its colas, and the strength of its stems are all elements of a plant’s phenotype.
A plant’s physical characteristics are ultimately determined by the environmental conditions under which it is cultivated. This is why two clones with an identical genotype can have different phenotypes. If two clones of the same plant are taken by two different growers and cultivated in different grow setups, differing climates, grow mediums, and other environmental factors will alter the color, shape, strength, and yield of each plant — all of which, in conjunction with the genotype of the original plant, will result in two separate phenotypes.
The Difference Between Genotypes and Chemotypes
While genotype determines the physical characteristics of the cannabis plant, and phenotype represents its observable traits after environmental exposure, a plant’s chemotype represents its chemical characteristics, i.e., its cannabinoid and terpene ratios. Cannabinoids are the cannabis compounds responsible for the plant’s euphoric and therapeutic effects, including tetrahydrocannabinol (THC) and cannabidiol (CBD). Terpenes provide the plant’s aroma and flavor, and influence effect by interacting with cannabinoids.
The ratio of cannabinoids, terpenes, and other metabolites found in the cannabis plant make up its chemotype, and they are also determined largely by the plant’s genome. This isn’t to say that environment doesn’t also play a role in determining a cannabis plant’s phenotype. But it’s the plant’s genes that dictate the possible range of chemotypes that the plant can produce under a given set of environmental conditions.
The genome essentially tells the plant, “If you are exposed to X nutrients and Y type of environment, you will produce Z chemical metabolites.” At the same time, two genotypes with the same nutrients and environment will produce two different cannabinoid and terpene ratios. The chemotype develops much more consistently with the genome than does the phenotype.