Genetics, Breeding and Selection Oh My!

Discussion in 'Cannabis Breeding' started by Indica Kid, Jun 7, 2009.

  1. #1 Indica Kid, Jun 7, 2009
    Last edited by a moderator: Aug 21, 2009
    Hey GC, I decided to write up a little piece on Genetics and Breeding.

    I will write all of this myself, although the information will be comparable to info readily available online. My genetic info will be based on that found on many sites, and my breeding info will be primarily based on the methods used by widely acclaimed breeder DJ Shorts. Let’s start with genetics:

    Much like those seen in humans, a plant’s genes are what determine its characteristics. I’m not a genetic scientist but I have a basic understanding of genetics and figure I might as well pass on my basic knowledge to you.

    A true-breeding plant is one that, when bred with either itself, or another of the same true-breeding plants, will produce the same characteristics in all of its “children”. Put very simply, it’s genes for any given characteristic are the same, without recessive genes hiding in the background.

    For the sake of simplicity, we are only going to look at one characteristic of plants: leaf structure. Let’s take a P1 plant (parent, 1st gen), a pure Sativa. Its long/narrow leaf genes will be represented by “AA”. Another P1, this time a pure Indica (short/fat leaves), will be represented by “aa”.

    Well one of these plants is going to have “dominant genetics” (we’re going to assume the Sativa), which means that, although the F1 (Hybrid 1st gen) plants will carry the recessive genetics, it will show long/skinny leaves. Here is an image to help illustrate this point:

    Since each of the possible phenotypes of the hybrid plants will have the dominant “A” gene, they will all have its physical traits (long/skinny leaves). However, lets see what happens when we cross the F1 hybrids with each other:

    Now we see three different types of genes:

    1: AA, this plant is essentially the same true-breeding hybrid as the original Sativa, its genes are dominant sativa leaves which means it will never produce a Indica leaves in a child plant.

    2: Aa, these plants are the same as the F1 hybrid we created earlier, it will have the recessive Indica genes but will only show the Sativa genetics.

    3: aa, these plants will essentially be the same true-breeding hybrid as the original Indica, it’s genes are the recessive, but because both the genes are the same, it will show its Indica heritage.

    IN CONCLUSION: This is a very basic explanation of genetics designed only to show you that it usually takes a minimum of two generations to create a true-breeding trait. In order to create a plant that is true breeding in several traits the process is far more complex because you must lock in each trait, while making sure the genetic line doesn't lose the other traits you are looking for. The dominant genes won’t be simply “Indica or Sativa” as I portrayed in the explanation, each plant will have genes that determine every single characteristic, whether it be height, leaf width, flowering time, trichome development, THC to CBD ratio, etc etc etc


    Lets discuss breeding now that you have a basic understanding of genetics, like I said earlier, I am going to base most of this off the methods used by DJ Shorts:

    First off, everyone should go into their own breeding experiment with a specific set of phenotypes of each characteristic in mind. You should decide what you want in each of the following variables:
    Plant Structure
    Flowering Time
    Trichome Development
    Sativa/Indica High

    Breeding is primarily just the act of careful selection. In order to have the widest variety of F1 hybrids to choose from, we are going to cross a pure Sativa with a pure Indica. This cross will produce hundreds of phenotypes with a vast array of variances from plant to plant. Your selection skills really begin to come into play at this point.

    Its your job to know what to look for in males and females. I’d like to note at this point that since much of the judging done on females occurs after the plant is harvested, it is wise to take two clones off each female just prior to flowering her, after sampling your bud, you can pollinate the clones of whatever female you prefer.

    With males, you don’t necessarily have to clone them as you can just shake pollen into a freezer bag, vacuum pack it and freeze it. Pollen carefully stored like this should last a few months, although it’s best if it is used within a few weeks. Pollen that is stored like this should be used immediately after thawing.

    In selecting males, you want to eliminate males as they display un-desirable traits. If one flowers early, trash it. If one grows at a VERY rapid rate, trash it, these genes will typically carry over into female “children” and they will dedicate more energy towards growth, and less towards producing large, thick buds. Also, it’s interesting to note that males seem to be the dominant factor in how strong the bud’s scent is, while females seem to contribute the type of scent. Any male that has weak scent should be trashed (unless that’s what you’re going for). In order to best determine the strength of scent, it’s best to smell the plant towards the end of the “dark period” in your lighting schedule. To best smell the plant, rub the plant’s stem somewhere in the middle and smell it. Although the males don’t grow bud’s, the clumps of pollen sacs will still be genetic indicators of what type of buds it’s children will grow, if a male has sparse, whispy pollen sacs, trash it. You want the pollen sacs to be tight and thick.

    When selecting females, the primary two things you should be looking for, are the scent you desire, and the high you desire. In any breeding program I would start by stabilizing those two traits, once you’re done with that, focus on any other phenotypes you’d like to chase.

    When you pick the males and females you desire, cross them with your favorite pollination method. I should say, occasionally you will pollinate a group of females and your F2 hybrids, will have none of the desired phenotypes. In this instance, you are simply experiencing a dominant gene in each of the children, another cross should yield 25% of the phenotype you are looking for.

    Good Luck Blades, Breed On!!!
    Indica Kid

    Attached Files:

  2. possibly should be a sticky icky icky! nice write up!
  3. Nice writeup! +rep

    Anyone interested in this should also read "Marijuana Botany", more specifically
    Chapter 3 which deals with Genetics and Breeding

    :bongin: ~Experimentalist
  4. Nice job.
    Prized males should be kept as father/donor plants, not just harvested once and let go. I bonsai all my moms and dads for efficiency.

    I guess it all depends on what an individual is after.
  5. Great information.
  6. Thanks guys! Hopefully this helps a few fellow GC members
  7. Bumpitybump
  8. Good thread. Every breeder or future breeder should know this.. ;)

    Are you going to breed your auto flowers IK?

  9. And I'm glad you did! Thanks for the write-up and it knocked loose memories of high school biology. Who woulda' thought it would've been applied to this :p

    Wel done and I second the sticky motion!

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