A Comparison of the Sexual Expression, Biomass, Cannabinoid Content, and Seed Production in XXX and XXY Triploid Cannabis

Cannabis is a multi-billion dollar industry reliant on unpollinated genetically female (XX) plants, as pollination reduces cannabinoid yields and flower quality. The mechanism behind the sexual expression of C. sativa is unclear. This study examines the sexual characteristics of homo- and hetero-gametic triploid cannabis plants (XX(X/Y)) to understand the role of the Y chromosome in cannabis sex determination. Heterogametic triploids were produced by crossing a male diploid C. sativa cv. Durban Poison (2n = 2x = 18 + XY) with a tetraploid female C. sativa cv. Higher Education (2n = 4x = 36 + XXXX) confirmed by flow cytometry and PCR. Measurements include fresh and dry plant weight, dry flower weight, seed counts, seed weights, and cannabinoids quantified using liquid chromatography. Results showed 44.4% of plants were XXY ( n = 8), with 75% presenting a monoecious phenotype ( n = 6). Of these, 50% produced predominately male flowers ( n = 3), while the rest produced predominately female flowers. Plants with predominately female flowers had higher yields and cannabinoids compared to predominantly male plants. XXX genotypes outperformed XXY in several metrics. This study enhances our understanding of C. sativa sex determination and offers insight into breeding and cultivation strategies utilizing triploid cannabis.