New Study Identifies Universal Genetic Marker for Early Sexing of Marijuana Plants

OG Article By Anthony Martinelli in News, Studies

August 29 2025

Researchers from University College Dublin have developed what they call a breakthrough method to determine the sex of cannabis plants at an early stage of growth.

The study, published in Planta, introduces CsPDS5, a highly conserved genetic marker that enables precise, affordable, and reliable sex identification using a simple PCR-based assay. Cannabis is primarily dioecious, with “female and male flowers develop[ing] on separate individuals, which is controlled by an XY sex determination system: females have two X chromosomes and male plants carry an X and a Y chromosome,” the study explains. While adult plants show “a high degree of dimorphism,” the authors note, “at early stages of development before the onset of flowering, this sexual dimorphism is not present.” This has created inefficiencies for both medical and industrial cultivation, as plants cannot be reliably sexed until flowering.

The researchers report that their new method “relies on a gene polymorphic between the X and Y chromosomes and therefore requires only a single PCR with one pair of primers.” The targeted marker, CsPDS5, is present on both chromosomes but includes a restriction enzyme site only on the Y-linked version. This makes it possible to “allow early sex identification and hemp selection” through a single PCR reaction and enzyme digestion.

The team tested the approach on more than 500 samples across 14 hemp cultivars and six crosses, and found that “the genetic and phenotypic sex matched, showing an accuracy of 100%.”

To broaden its application, they also “adapted it into a high-throughput TaqMan assay” suitable for breeding programs, and sequence analysis confirmed that CsPDS5 is “extremely conserved across the different cultivars.”

According to the authors, the assay provides “a robust, reliable and affordable PCR-based method to determine the sex genotype” and could serve as a blueprint “to discover new sex markers, not only in C. sativa but also in other dioecious plants and other organisms with 2 sexes.”