The cannabis plant is a dioecious plant in that it presents as male or female plants. Sex organs present at approximately 6 weeks of growth and females are selected for cannabinoid generation. Male plants have an XY chromosome structure and female plants have XX chromosome structure much like humans.
Visual inspection of a male plant (XY)
Visual inspection of a female plant (XX)
DNA based gender determination allows early identification and removal of male plants long before visual sex identification is possible. This is important to maintain female flowers rich in cannabinoids. Once females are pollinated they divert their cannabinoid synthesis energy into making seeds and significantly reduce cannabinoid yields. Failure to detect a male plant amongst a female growth room can destroy a valuable crop. This is currently done visually at 6 weeks of growth and can be error prone.
With genetics, this can be performed at the first sight of a cotyledon. As soon as a leaf presents itself, DNA can be extracted and sex determined in under 1.5 hours in 96 well formats.
Sensitive genetic tests can be performed on a sample as small as a leaf hole punch
DNA based sex typing of cannabis was first described by Mandolino et al. with the MADC2 marker set. While this work was revolutionary, the assay required visual interpretations of gel electrophoresis bands to determine the sex and did not deliver a binary result compatible with qPCR.
Medicinal Genomics sought to improve these markers and decoded the genomes of 2 male strains (Wifi and Grape Stomper 4). These DNA assemblies were screened against 12 female genomes to find male specific sequence. qPCR primers were designed to make a more accurate and reliable male vs female test.
Male Cannabis Genome Project generates thousands of high quality putative Y chromosome Sequences for better Y detection