How to do an F1 Cross
Suppose you have an awesome strain, and you want to make a high CBD version. Here’s the traditional way of doing it.
First, you want to make sure your strain doesn’t already produce CBD. You also need to find a male plant from a strain that makes lots of CBD. You can get males by growing a few plants from seeds. Next, you breed these two strains in what’s known as an F1 cross. Let’s draw a Punnett square to diagram how different versions of a single gene are exchanged during an F1 cross. It looks like this:
How to do an F2 Cross
Identifying High CBD and High THC Plants
At Delta Leaf we can identify whether a plant contains the Bt allele, the Bd allele, or both. This saves time and money by identifying the plants you want immediately after germination, instead of waiting months to observe the phenotype. We can also identify whether a plant carries the male, or “Y”, chromosome. Sample collection kits are available now on our website.
How Are THC and CBD Made?
Determining Levels of THC and CBD
When a male plant pollinates a female plant to make seeds, those seeds get one copy of each gene from mom and one copy of each gene from dad.
If a plant has two copies of the Bt allele , then the plant will basically only produce THC. Likewise, if the plant has two copies of the Bd allele then the plant will only make CBD. However, if the plant has one copy of the Bt allele and one copy of the Bd allele, then it will have a mix of THC and CBD. This is why most strains have either high THC, high CBD, or something close to a even ratio with neither cannabinoid becoming much higher than 15% dry weight. Check out the image below to get an idea of what the different combinations of THC (Bt) and CBD (Bd) alleles look like at the genetic level.
At Delta Leaf we can identify whether a plant contains the Bt allele, the Bd allele, or both. This saves time and money by identifying the plants you want immediately after germination, instead of waiting months to observe the phenotype. We can also conduct gender identity tests to analyze male vs. female cannabis and hemp plants through detection of the Y-chromosome. Sample collection kits are available here on our website.
Please contact us ahead of time if you want to get your plants tested for the Bt or Bd allele.
How To Start Growing Cannabis
When the time comes to start a new batch of plants, there are essentially two main methods a grower can choose. The most common method is to make clones, or genetically identical copies of a “mother” plant. Cloning involves cutting off a piece of stem with some leaves, then planting it under conditions which make the stem grow roots and eventually a whole new plant. The second method, using seeds, is probably what people typically think of when growing plants. That’s because you can buy packs of seeds for vegetables or almost any other plant at the grocery store. Almost all major crops are grown from seed, and for good reasons. Modern agriculture has benefited from years of science that enables breeders to produce consistent batches of seeds; however, cannabis breeders haven’t had those same tools available, until very recently. An example of a technology that helps breeders speed up development of new strains is DNA testing, like what we offer here at Delta Leaf.
Advantages of Seeds and Clones
Compared to clones made using traditional methods, seeds produce plants that grow larger and are more disease resistant. Growing from seed also eliminates the risk of transferring "stowaway" pests such as mildew and gnats, which can show their face and cripple your garden after months of work. Plants grown from seed are reported to be heartier and larger because they establish what's called a taproot, which is the large central root that pokes out of a seed when it first germinates. The taproot grows straight down, anchoring the plant and sprouting all the lateral roots that extend outward. While clones might seem to save time because they're bigger when they enter your garden, it's not hard to plan ahead so that you have seedlings ready of similar size when you would normally buy or start new clones for your next grow cycle. When proper planning is used, seeds can easily replace clones in grow operations with high turnover (frequent harvests). Using Plant DNA Sex Testing also drastically improves the cost-efficiency of growing from seed.
Plants that are started from seed have also been reported to produce a larger harvest than clones that are started at a comparable stage. Finally, the most important aspect of plant health that is affected by cloning is the acceleration of senescence (deterioration due to aging). Each time a clone is cut from a mother plant, it creates a minor stress of infection and tissue damage that accumulates negative consequences over time. Worse, if a clone is taken from a clone (which must be done after a mother becomes exhausted), then senescence will only be accelerated further each generation you get away from the original seed. The multitude of advantages that seeds offer regarding plant health and vigor make them invaluable to many growers.
Seeds vs. Tissue Culture
Many of the disadvantages inherent to clone growing can be overcome using plant tissue culture, however, this requires costly infrastructure and continuous maintenance of culture stocks. Cannabis plants grow very rapidly and a single plant is able to produce thousands of seeds. These factors diminish the potential commercial benefits of using tissue culture (a.k.a. micropropagation) to supply clone stocks. Further, seeds are stable for long periods of time under a wide variety of environmental conditions and are easily germinated with high success rates. An individual seed also requires less space to store it than a micro-propagated plant. When consistent genetics become available as seed stock, the cannabis industry will no longer be reliant on clones to produce a consistent product. Both of these methods (seed production and tissue culture) can produce disease-free and genetically predictable starting points; therefore, overhead costs of maintaining seed stocks vs. maintaining tissue culture stocks will become the major factor in determining how cannabis genetics are propagated in the future - and the clear winner is seeds.
Below is a list of reputable seed banks you can purchase seeds from. This is not an endorsement for any of the following sites. Always check your local laws surrounding cannabis before purchasing seeds online.
For more information about the differences between seeds and clones, check out these other great articles:
1. Daniel Zohary, “Unconscious Selection And The Evolution Of Domesticated Plants,” Economic Botany 58, No. 1 (January 1, 2004): 5–10
2. Doyle Mckey Et Al., “The Evolutionary Ecology Of Clonally Propagated Domesticated Plants,” New Phytologist 186, No. 2 (April 1, 2010): 318–32
3. Mohan P. A. Marimuthu Et Al., “Synthetic Clonal Reproduction Through Seeds,” Science 331, No. 6019 (February 18, 2011): 876–876
4. Rachel S. Meyer, Ashley E. Duval, And Helen R. Jensen, “Patterns And Processes In Crop Domestication: An Historical Review And Quantitative Analysis Of 203 Global Food Crops,” New Phytologist 196, No. 1 (October 1, 2012): 29–48
5. Rachel S. Meyer And Michael D. Purugganan, “Evolution Of Crop Species: Genetics Of Domestication And Diversification,” Nature Reviews Genetics 14 (November 18, 2013): 840.
6. Trevor A. Thorpe, “History Of Plant Tissue Culture,” Molecular Biotechnology 37, No. 2 (October 2007): 169–80