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Breeding for Novel Chemotypes

Here we will discuss more advanced breeding methodologies in our endeavor to produce novel chemotypes with similar "bag appeal" as that of the high THC cultivars we all know and love. Unfortunately, most true breeding CBD, THCV, CBDVA, CBG, . . .  chemotypes are lacking in their ability to compete in the marketplace due to several factors: lack of terpene diversity, airy/fluffy buds, lack of available cultivars, scarcity of seed stock, long flowering time, low overall cannabinoid production, etc.

A little background on myself: I started growing in the late '90s. Due to my geographic location, obtaining seeds and clones was rather difficult so I had to start breeding to ensure I had seed stock. I went on to college and finished bachelor degrees in Biology and Chemistry, and later a master's in Biology. I spent a lot of time studying genetics and various qualitative and quantitative methods of genetic research. Now back to the topic at hand.

For this discussion I will use the term phenotype to describe the visual physical differences and chemotype to describe ratios of cannabinoids.

So this past year I did five acres of hemp strains Otto II, BaOx, and Cherrywine. I planted a total of of 20,000 regular seeds. Throughout the year I noticed significant variation in phenotypic expressions within the individual lines. The Otto II is mainly sativa dominant and flowers in 9-11 weeks. BaOx has a wide variety of phenotypic expression and flowers for 8-10 weeks. Cherrywine is all over the place, but has some plants with amazing terpene profiles and bud structure, and flowers for 9-11 weeks. Terpene profiles are very very similar among all three cultivars, despite differences in their lineages. The one trait they all breed true for is CBD dominance.

I have a gas chromatograph with FID so I can look at the ratios of CBD:THC and the Otto II and BaOx are pretty stable with 90% testing in the 20:1 range. The Cherrywine seems to be a bit more variable with ratios from 15:1 up to 50:1. I selected the highest CBD:THC ratio males that were culled from the field. Having to sex 20,000 plants with just me and the wife was no simple task! I also selected for structure and for early flowering time.

Currently I have a 45:1 Cherrywine male in a tent with the highest ratio female clones from the field and they have about five-six weeks of flowering left. Once the seeds are ready I will be able to chemotype the Cherrywine x Otto II, Cherrywine x BaOx, and Cherrywine F2. I also have the following THC dominant plants in the tent as well: Key Lime Pie, MAC, OGKB, and Sensi Star. I am hoping to find offspring that exhibit similar physical and terpene profiles of the THC dominant strains, but retain the CBD dominant cannabinoid chemotype.

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Fantastic stuff. I'm incredibly interested in the hunt for THCV phenotypes, though they're quite scant. Difficult to source quality seeds that have the potential, difficult to find phenos with a noteworthy (5%+THCV) chemotype, and even more difficult still to get them to breed true. I'll cut to the chase - is there a simple way aside from male reversal to find THCV phenos among the male part of the stock?

Love the attention to detail on this thread. Pulling up a chair for this one! 🍿

THCV is a very interesting cannabinoid. It has shown significant medicinal use especially in diabetics. It has also been shown to reduce increased heart rate caused by THC, as well as impairing other effects of THC - like slowed verbal recall and short term memory loss. There have been some mixed result on THCV as a weight loss aide, but it seems that it does help control weight gain, though the exact mechanisms are not wholly agreed upon. Now, as far as breeding for high THCV plants, we'd want to approach this just like we would with any other cannabinoid - find males and females that contain THCV synthase genes, selecting for those with the greatest expression thru GC or HPLC testing, and start line breeding for those traits. The trick is to develop as many copies of the THCV synthase genes as possible. This occurs at the molecular level through various processes like crossing over and recombination. Recombination or crossing over occurs during fertilization (prophase I). Homologous chromosomes – one inherited from each parent (or itself in reversal) – pair along their lengths, gene by gene. Breaks occur along the chromosomes, and they rejoin, trading some of their genes. The chromosomes now have genes in a unique combination. It will be in that unique combination that we will find our desired chemotype. I am working with a (Malawi x Sour Diesel) x Feral Hemp that has up to 8% THCV. I will be growing a few out full season under the sun to see if I can hit 10%! As far as a way to find THCV chemotypes among male plants, I would recommend testing and then once you've identified the highest THCV chemotype, reversing and then repeating the process. Because non-synthetic, naturally derived THCV is relatively rare, it can bring a premium as an isolate.

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