Mutagenesis-Inducing Variation

Marijuana Horticulture

by Jorge Cervantes

If variation does not exist for the trait or traits of interest, or cannot be found in other populations, it is theoretically possible to induce variation by exposing seeds or other tissues to radiation, alkylating agents, or other mutagens such as colchicine or EMS (ethylmethylsulfonate). These treatments cause changes at the DNA level that have the remote potential to result in desirable, novel phenotypes.

There is much rumor and speculation about this technique amonst breeders and growers. It’s a common myth that treating seeds with colchicine and growing the plants results in more potent cannabis plants. Let’s put this myth to rest; it is completely untrue. While the possibility does exist on a theoretical level, no valid experiments have ever shown this to be true. Potential breeders would be better off using their time an space for selecting better plants than trying this technique as a method for improving plant stock. That being said, let’s take a look at the theory behind the concept.

Imagine you have a population of plant which, when grown from seed and inbred within the population, consistently produces high-THC plants. It is theoretically possible to treat many of these seeds with a mutagen, grow and inbreed the seeds, and find plants in subsequent generations that produce no THC. These mutagens can destroy genes along a chromosome, and when copies of this chromosome are inherited by future generations, a new or “novel” phenotype can appear. In our example, the no THC condition is the novel phenotype.

These mutations, however, occur at random and are extremely unreliable. The probability of finding plants which have the desired mutation in the gene of interest is very low. A breeder may treat many thousands of seeds, grow 100,000 plants, and still not see the desired altered phenotypes. This technique is costly in both time and space. It is often used in breeding of “legal plants” when growing our thousands of individuals and searching for these novel phenotypes is not problematic. Performing such population screens in cannabis is not practical, especially for clandestine breeders. The potentially hazardous nature of these mutagenic agents is another very good reason to choose other breeding options. Inducing variability is likely not the best option, at least for the hobby breeder.