Interview: Richard Philbrook, Molecular Biologist - Dark Heart Labs

Tell me a bit about the triploids/tetraploids that were discovered at the Humboldt Seed Co. 2023 Phenotype Megahunt.

I help Nat and Ben to breed triploids by creating tetraploids from normal plants. Crossing a diploid with these tetraploids makes the seedless triploids, similar to how watermelon, banana, etc are made. An interesting phenomenon in plants is that they can do this work naturally sometimes! There are a lot of naturally occurring polyploids, like the Russet potato. During the course of research to create our triploids, we discovered that cannabis actually makes polyploids on its own at a low rate. There have been triploids floating around the cultivation scene for years, unknown to people. In fact, one of the winners from the 2018 phenohunt, Hades OG, turned out to be a natural triploid. The popular clone-only strain Mac1 is also triploid. Once we knew this could happen naturally, we started testing more plants, leading to finding a natural triploid in one of the Stoopid Fruits cross winners at this year's phenohunt.

After the phenohunt was over, Erik Christiansen noticed some interesting trichome morphology in the polyploids we had made intentionally while going through the macro pictures he had been taking. He happened to be visiting a farm nearby one day, Casa Flor, so he, Jorge Cervantes, and Ben Lind stopped by with a sample from the field that had this same interesting trichome morphology. We tested the plant, and discovered the first confirmed natural tetraploid. It was one of the highlights of my career so far, having legends that I've looked up to for years in the lab making discoveries in real time.    

Why are these discoveries significant?

Natural polyploidy has a lot of implications for how plants evolve and form new species, so from a purely scientific standpoint it is very interesting to know this can happen and might explain some of the interesting quirks in the Cannabis genome. Beyond basic scientific research, having natural polyploids can also ease the fear some people might have about this new breeding technique we are applying. Polyploids are out there, they've been out there and you've probably smoked one already!

What are the future implications of these discoveries?

Besides the sterility aspect of triploids, one thing that really excites me about this technology for the future is how breeders will use the increased genetic diversity and gene combinations polyploidy offers. More chromosomes = more genes and combinations of genes, meaning we can create truly unique varieties with a diverse range of cannabinoid and terpene ratios not seen before. Related to this, the concept of stacking certain genes using polyploids is also exciting. A lab at the University of Connecticut (UConn) has applied this technique to the autoflower gene, creating triploids that have two copies of the autoflower gene and one copy of the photoperiod gene to make "fast-flowering" plants that start flowering faster than diploid fast flowers. I can envision a range of triploids with different copy numbers of the autoflower trait tailored for specific latitudes and growing conditions. And that is only one gene! The possibilities are limited only by the creativity of breeders.

What stood out to you as the most exciting thing you saw?

Easily the triploid Royal Highness x Fortune Cookies at Burr's Place in Calaveras County, California. Those plants combined the triploid technology with another genetics idea we have also worked on, measuring zygosity and diversity using genotyping analysis. The inbred tetraploid royal highness was very different and homozygous from anything else we tested, so we expected it to combine well with other strains and bring out hybrid vigor, along with hopefully getting a boost in yield from triploidy in whatever cross was made. And the proof was in the pudding. Some of the most uniform, highest yielding plants I've ever seen. It was a great moment to see both the field and lab approaches to breeding combine to produce exceptional results.

Link to recently published article where Richard Philbrook is first author - “Naturally Occurring Triploidy in Cannabis” https://www.mdpi.com/2223-7747/12/23/3927