Aneuploidy

Aneuploidy refers to an abnormal number of chromosomes in a plant cell—either missing or extra copies beyond the typical diploid (2n) set. Cannabis normally carries two sets of chromosomes (2n=20), but aneuploid plants may have 19, 21, or other variations. This chromosomal imbalance typically arises spontaneously during seed development or in tissue culture and often results in reduced vigor, fertility problems, or stunted growth. Breeders generally treat aneuploidy as an undesirable trait because it compromises stable inheritance and reliable phenotype expression across generations.

While aneuploidy is usually eliminated during selection, researchers have occasionally documented it in stressed or aged seed stocks. Understanding its markers helps breeders identify and cull unstable plants early, ensuring seed lots maintain chromosomal integrity and consistent performance.