Marijuana Horticulture: The Indoor/Outdoor Medical Grower's Bible

is heterozygous, it has two different alleles for a given trait (hetero = different).
Dominance
    Consider two true-breeding varieties; a white pistil variety and a variety showing only pink pistils. Both conditions are true-breeding and therefore homozygous; in each case sexual reproduction of each group separately leads to only pink pistil or white pistil plants respectively. An F1 hybrid, or first generation cross of these two varieties, results in only white pistil plants; no pink pistils are seen regardless of how many F1 seeds are grown.
    Upon sib mating of these F1 plants (crossing brothers to sisters, or mating F1 siblings), the resulting F2 generation produces 75% white pistil plants and 25% pink pistil plants. Notice the “disappearance” of the pink pistil plants in the F1 generation, and their subsequent “reappearance” in the F2 generation. In this case, white pistils are said to be dominant over pink pistils, and pink pistils are said to be recessive to white pistils.
    Again, let’s consider the phenotypes seen, and provide symbols and deduce the genotypes:
    P1 - White pistils × P2 - Pink pistils

    F1 generation
    (All white-pistil plants)
    F1 male × F1 female

    F2 generation
    25% pink-pistil plants, 75% white-pistil plants
    Remember our rule about naming the genotype symbol based on the first letter of the recessive condition, in this case pink.
Phenotypes: Pink (recessive) and White (dominant)

    This 75% can be broken down into 2 genotypic classes, PP and Pp.
    When we cross Pp × Pp plants, we get three possible combinations of genotypes. 25% PP, 50% Pp, 25% pp.

    Therefore we know the 75% white pistil plants are actually 50% Pp + 25% PP, for a total of 75%.
    Recessive: An intra-allelic interaction such that an allele of one parent is masked by the presence of an allele from the other parent plant, in the expression of a given trait in the progeny. The recessive trait is not shown in the first generation of progeny (Fl) but will reappear if siblings are mated, and the F2 progeny will result in 25% plants showing the recessive condition.
    Dominant: An intra-allelic interaction such that the presence of an allele of one parent masks the presence of an allele from another parent plant, in the expression of a given trait in the progeny. Only the dominant trait is shown in the first generation of offspring. Of the F2 generation, 75% will also show the dominant condition.
Primary Components of a Breeding Program
    1 - Develop a vision or a breeding goal.
    Every breeding program should begin by developing a breeding goal. Why are you trying to make seed? What are you trying to accomplish by mating these sets of parents? You might be trying to make a seed population that represents the traits of an ideal, or mostly ideal plant you have previously selected. In the case of the latter, you might be trying to add new traits to your mostly ideal plant and incorporate these new traits into a new seedline. Some may just want some seeds to plant for next year’s crop. Think of your breeding goal as your final destination; the breeding process is the roadmap or route to get to that goal.
    2 - Find or Create variability.
    Finding variable seedlots these days is certainly not a difficult task, because very few breeders take the time to stabilize or fix certain traits within a given breeding population prior to release. Your starting seed stock likely represents a range of variation for most traits, depending on the source of your initial starting material. The sad reality is that most of the seed industry today focuses more on creating seed for sale than on developing improved or even uniform plant stock. As a breeder looking for germ plasm to work with, this leaves unstable populations with ample variation for future selection. If searching for variation, this could be considered a good thing. However, since true-breeding stable plants are what breeders look for when choosing stock for their own breeding, this is a hindrance as well. It is much easier to breed with true breeding plants because one can see patterns emerging in a predictable manner in subsequent generations, and thus expect reliable, consistent results when hybridizing known true-breeding parents. This can only be achieved if the breeder is using true-breeding starting parent stock. Due to the lack of commercially available true-breeding stock to work with, serious breeders must stabilize their initial breeding stock before beginning the