From DNA to CBD, How Genetics Could Be the Key to Boosting Cannabinoids
Cannabidiol (CBD) is now one of the most discussed and craved chemicals on the market. The three famous letters drew in 6.4 million Google searches in the United States alone during April 2019 – outpacing other leading wellbeing-related search terms, such as acupuncture, meditation, and veganism. And this curiosity isn’t idle; US sales of cannabis- and hemp-derived CBD products are expected to surge to $20 billion by 2024.
With such values at stake, cannabis cultivators aren’t taking any chances with their CBD contents. Since the passage of the 2018 Farm Bill last December, the total number of US acres used for cultivating hemp has increased by 328 percent.
But is there a better way of boosting CBD supplies other than just growing more hemp? With the top tools of genetic science now at the cannabis cultivator’s disposal, there just might be.
Galvanizing green genes
“We have several assays designed for multiple different markers across the cannabis genome,” Anthony Torres explained. As a research scientist for Steep Hill, one of the first commercial medical cannabis labs in the US, Torres spends his time carrying out biochemical and genetic tests on multiple cannabis cultivars to determine their cannabinoid contents. And through such studies, it hasn’t escaped Torres’ notice which of cannabis’ green genes are vital to CBD production.
“For a couple of CBD markers, we’ve refined the assays to identify individuals that will produce CBDA at a ratio greater than 20:1,” Torres said during Analytical Cannabis’ recent online symposia.
CBDA, or cannabidiolic acid, is the chemical precursor to CBD. While not as notable as its successor, the compound was been shown to be a thousand times more powerful than CBD in binding to a specific serotonin receptor linked to anti-nausea and anti-anxiety effects.
Working with a cannabis cultivator in Tennessee, Torres and his team at Steep Hill tested and bred generations of hemp to produce a new, high-CBDA variety.
“When we looked at the F1 (first generation) genotypes, we identified the classes that matched the parents and used the chemical phenotype information to identify which diverse individuals would produce high CBDA,” he said.
A mixture of standard genetic tests and some unique innovations, Torres’ genotyping process relies on fluorescent markers and equipment to carry out polymerase chain reactions (PCRs) – a typical method of replicating DNA.
“For a CBD marker, a specific segment of the CBD gene will create lots of copies of this CBD marker using PCR,” Torres explained. “The [PCR] process will raise the temperature to 95 degrees, [after which] the double stranded DNA will come apart and mix with the fluorescent dye that is emitting light to the detector of the instrument. As the nucleotides reanneal, you’ll observe a differential DNA sequence. So if there’s any kind of diversity, you’ll observe a unique melting signature.”
It may sound complex – and it is – but Torres’ test is routine enough to be easily replicated for any grower looking to find and boost their CBD genes, as Torres’ study on the Tennessee hemp demonstrated.
“We identified the blue group individuals as high ratio CBD-producing genotypes that had the capacity of producing ratios of CBD 20:1,” he told Analytical Cannabis. “[These] were crossed with red group individuals and we observed a diversity of different genotypes that were all high CBD-producing.”
“So through chemical phenotyping and chemical tracking, we helped the breeder identify some key F1 individuals that will be carried out through production and used to produce high CBD individuals.”
The birds and the bees – and the CBD boost
Traditionally, when cannabis cultivation was a more clandestine process, growers didn’t have access to such genetic aids. If a cultivator wanted to encourage a particular characteristic in their crop, they’d have to taste, smell, and smoke the plant just to know what attributes it had in the first place.
But whether in 1979 or 2019, the process of selectively breeding cannabis is still the same: both a male and female plant have to be identified. Fortunately, genetic tests can help on that front, too.
“The female flowers are what are commercially sought after,” Torres explained. “And within the last decade or so breeders have been utilizing chemical potency analysis to track traits as well. And they can use those services from Steep Hill.”
As the bud-producing sex, feminized plants are coveted for their THC and CBD, while pollen-producing males are often regarded as worthless.So by clearly identifying CBD-producing females, growers can pair them with masculinized flowers to create a second generation, highly potent in CBD.
“Since its inception, we’ve tested nearly 10,000 individuals for sex genotypes,” Torres added. “Our assay targets a very specific DNA element that we’ve identified in true male cannabis that possess a Y chromosome.”
“We’re fully aware that the sex expression of cannabis is very diverse,” he clarified. “But there are true, genetically-diverged male individuals.”
As another PCR-based method, Steep Hill’s sex determination assay functions a lot like its cannabinoid test.
“We track a fluorescent probe of DNA through a PCR, and as the copies of DNA accumulate and cross a threshold, we’ll observe a fluorescent signal,” Torres said.
Although it’s not suited to every cultivation strategy – outdoor growing notoriously results in natural pollen distribution – Steep Hill’s sexing assay could help countless cultivators curate an ideal CBD-rich crop. And twinned with the company’s cannabinoid-identifying assays, the test has the potential to cement genetic screening as a key tool in a cannabis cultivator’s arsenal.
“There’s more genetic diversity in cannabis than there is in humans,” Torres added. “And the potential for breeding definitely could be maximized through biochemical and genetic applications.”
This article originally appeared in Analytical Cannabis’ Advances in Cannabis Cultivation Science ebook in December 2019.
Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a bachelor’s degree in biology from Newcastle University and a master’s degree in science communication from the University of Edinburgh.
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From DNA to CBD, How Genetics Could Be the Key to Boosting Cannabinoids Cannabidiol (CBD) is now one of the most discussed and craved chemicals on the market. The three famous letters drew in 6.4
THC & CBD – these are our main cannabinoids and it’s important to understand the relationship between them. As your plant is producing cannabinoids, it will be producing both (there are strains with negligible THC, but none that are producing CBD levels worth your effort). This becomes a balancing act; to find the right strain not just for the growth qualities, but also for the levels you’re targeting. In that, timing becomes very important. Hemp will increase its cannabinoid production at the end of its flower cycle – BOTH your THC and CBD values will be increasing. With that in mind, the timing of harvest is the point at which you produce maximum CBD, while staying within your regulatory requirements for THC. A quick look around and you will see what we mean, it’s in what is NOT said – claims of impossible CBD:THC ratios, but never a COA (Certificate of Analysis) to provide evidence…others give you the highest CBD content possible from their plant, but at that point their THC levels are far beyond acceptable. Always review the COA when you are looking to purchase hemp genetics.
CBG & CBN – these are the other emerging cannabinoids of interest. The interest in these is growing and we are continuing our research and breeding program for these cannabinoids. True breeding and stabilization is not a fast process…we are very excited about what’s coming in our future genetic releases for these specific cannabinoids, so stay tuned for future releases.
Some farmers will elect to start hemp seeds indoors and then transplant the clones into fields. While this is clearly more labor intensive, it can create a higher success rate and/or allows farmers to get a jump on the season. It is critical to maintain a moist environment – a dried seedling will be a dead seedling. While it is important to keep the plugs you’re propagating moist, do not oversaturate the seedling – it will drown or once sprouted, rot away (dampening off). Also understand that if propagating for a jump start on your season, the plants will have some adjustment issues when transitioning from artificial light to natural sunlight. This can be mitigated by introducing your starts to natural light slowly prior to transplanting outdoors (hardening off).
Planting of your hemp crop includes many variables and so here’s just a couple quick notes from us:
Hemp prefers moist, warm soil. Try to plant during expected rain times or run your irrigation frequently enough to keep the soil moist during transplant/planting.
Hemp does well with warmer soils – do NOT plant until soil temps are above 50 degrees and the higher the better.
Hemp does not do well in compacted soils or sowed deeply, it needs an easy shot coming out of the soil. Opinions range on planting depth from ¼” to 1” deep – we prefer the shallow end of this from our experience but the range of variables including soil composition, soil compaction, humidity, soil moisture, and temperatures mean there is no set answer.
Hemp does not do well in over saturated soils. It is best to plant hemp on fields with adequate drainage.
There has been a variety of opinions on the best spacing for high cannabinoid hemp fields: the initial opinion was to run plants at about 5’ spacing but we see many farmers adopting 3’ on center spacing with any adjustments for working rows. Some pros & cons on that from our experience are as follows:
-Larger spacing: cheaper seed costs, more row weeding, weeds able to establish and compete with hemp, less plants to harvest, larger stalks at harvest harder to cut, larger stalks not possible to harvest with standard farm implements, less plants to hang for drying, increased stalk mass, reduced plant management (male culling, inspection, etc).
-Tighter spacing: higher seed costs, less row weeding, weeds less able to compete with hemp, more plants to harvest, smaller stalks easier to cut, potential to use standard farm implements, increased plants to hang for drying, reduced stalk mass, increased plant management.
-Close spacing: not generally recommended – high seed costs, too many plants to harvest, too many plants to dry, too many plants to manage.
Below are tables to help you calculate your plant requirements based on plant spacing (on centers) or plant total. Keep in mind that these do not account for any working rows, windrows, etc. and adjust accordingly.
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