Study: Female Marijuana Plants Contain Nearly 17 Times More CBD Than Males, Researchers Identify the Exact Genes Responsible

A new peer-reviewed 0 published in iScience by researchers from the Institute of Bast Fiber Crops at the Chinese Academy of Agricultural Sciences provides one of the clearest molecular explanations yet for why female marijuana plants are dramatically more valuable for cannabinoid production than male plants. Using a combined transcriptomic and metabolomic analysis of male and female Cannabis sativa flowers, the research team identified 1,676 differentially expressed genes and 700 differentially accumulated metabolites that separate the two sexes at the biochemical level. The results show that these differences are not just structural or hormonal, but deeply tied to the genetic pathways that control terpene and cannabinoid synthesis.

The most striking finding was the cannabinoid disparity. Female flowers contained CBD levels 16.88 times higher than male flowers. CBD, CBDV, CBN and THC were all significantly more abundant in female flowers. By contrast, only CBDA and THCV were found at higher levels in male flowers.

According to the study, this difference is primarily explained by the density and function of secretory glandular trichomes. Under microscopy, female flowers showed a far higher concentration of active secretory trichomes, while the few trichomes present on male flowers were largely non-secretory. These trichomes are the primary sites where cannabinoids and terpenes are synthesized and stored.

The researchers identified several key genes that were strongly expressed in female flowers and are directly involved in terpene and cannabinoid synthesis pathways, including CsDXPS1, CsLOX2, CsLOX1.5, CsAAE18 and CsGGR. These genes sit at critical steps in the MEP and MVA pathways that produce geranyl diphosphate and olivetolic acid, the two foundational precursors to cannabinoids.

They also identified two transcription factors that appear to play an outsized regulatory role: CsMYC4 and CsMYB49. Both were highly expressed in female flowers and strongly correlated with cannabinoid and terpene abundance. These transcription factors are known in other plant species to regulate terpene synthase genes and trichome development, suggesting they are central switches that help female plants become biochemical “factories” for secondary metabolites.

In total, the team identified seven genes related specifically to glandular trichome development that showed strong positive correlation with cannabinoid and terpene levels. All but one of these were heavily upregulated in female flowers.

The study also found that 77 genes related to plant hormones such as auxin, gibberellin, ethylene and cytokinin differed sharply between male and female flowers. These hormone pathways are believed to influence sexual differentiation and may indirectly control trichome development and metabolite production.

Terpene production showed a similar sex-based split. Metabolomic sequencing identified 28 terpenes that differed between male and female flowers. Fourteen were more abundant in females, including several sesquiterpenes linked to antioxidant and anti-inflammatory effects that complement cannabinoids. Others were more common in males, but not at levels associated with high medicinal value.

Importantly, the researchers connected these metabolic differences back to gene expression through integrated pathway analysis. Phenylpropanoid biosynthesis, citric acid cycle activity, and ABC transporter pathways all showed sex-specific gene expression patterns that help explain why female plants allocate far more resources into secondary metabolite production.

The authors conclude that the results provide a “theoretical basis for the directional selection of female strains with high production and cultivation value.” In practical terms, the study offers molecular confirmation of what cultivators have known for decades: female plants are uniquely suited for cannabinoid and terpene production, but now the specific genes and regulatory systems behind that advantage have been identified.

This opens the door to more targeted breeding strategies, including selecting for strains that express higher levels of CsMYC4, CsMYB49 and other trichome-related genes, potentially increasing cannabinoid yields without changing cultivation conditions.

The study also highlights why male plants, while useful for fiber production, offer far less medicinal value due to their limited trichome activity and suppressed expression of key biosynthetic genes.

Researchers note that while the findings clearly map the genetic and metabolic differences between male and female flowers, further work is needed to experimentally verify how these transcription factors directly regulate trichome secretion.

Still, the work represents one of the most detailed molecular examinations of sex-based differences in marijuana plants to date and provides a blueprint for future breeding, selection and cultivation strategies aimed at maximizing cannabinoid production.