Cannabis in the wild is almost exclusively a diploid (2n) species. In diploids, every plant receives one set of chromosomes from each parent. Though rare, spontaneous mutations can occur that result in a doubling of the diploid genomes and lead to tetraploid (4n) individuals even in controlled breeding populations.
Dr. Hsuan Chen and Brendan Rojas, research plant breeders at Oregon CBD, designed a series of experiments to treat diploid cannabis tissue with compounds known to inhibit cell division. The process approximates the tetraploid-inducing events that occur in nature at a very low rate, but does so (now, after many experiments) in a more consistent manner. Treated plants must be screened using a flow cytometer--a device that can measure the physical size of a plant genome--and compared to their diploid counterparts to detect the desired doubling of genome size. Success results in tetraploids: plants with four sets of homologous chromosomes (4n) and an identical doubled version of the mother. This screening process is repeated a number of times in subsequent generations of cuttings to prevent reversion to the diploid state.
Tetraploid cannabis plants have been described by two other research groups (Mansouri and Bagheri 2017 and Parsons et al. 2019) and their findings mirror ours; distinct morphological changes and increased nutrient consumption are apparent, but chemical composition (ratios and total amounts produced) is relatively unchanged--albeit with a marked increase in aromatic compounds. So far, evidence suggests that tetraploids offer little if any performance increase over diploids, with the exception of louder olfactory notes.
The game-changer for farmers happens when tetraploids (4n) are crossed with diploids (2n); the resulting seed carries 2 copies of chromosomes from the tetraploid parent and 1 set from the diploid parent (3n). This traditional plant breeding process is well documented and has been used to improve many other crops, particularly those where seedless characteristics, essential oil production, and increased biomass are valuable agronomic traits. We are able to offer this revolutionary advancement through ploidy improvements of our newly developed, varin-rich total THC compliant hemp varieties--making for one of the most significant single-year advancements in the history of modern cannabis breeding.