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Feminized breeding (STS)
Hello friends,

I'm about to start experimenting with STS-based reversals and feminized breeding, and I'd like to share the results with you, so I thought I'd take a moment to define the technical terms I'll be using frequently. If there's any other terms or concepts you'd like explained, let me know and I'll see what I can do.

Terminology for STS breeding:

STS: Silver thiosulfate, a salt compound used in photography. In plants, silver interferes with, or locks out, copper, which is a necessary micronutrient. Making copper unavilable inteferes with ethylene signaling, and reduces expression of traits that are dependent on high levels of ethylene, such as female sex expression and fruit ripening.

Copper: a micronutrient that is necessary to assist certain enzymes in their function. Copper can become toxic at low levels, but a few parts per billion is adequate for plants to express their genetic potential. Because copper is needed at such low levels, it does not take much silver to overwhelm the available copper load and exert its effect.

Ethylene: One of the 5 plant hormones. The levels and ratios of these 5 hormones has a huge impact on the shape, strucutre, aroma, flavor, flowering time, and disease resistance of the plant. Hormones are the chemical messengers that allow DNA to 'talk' to plant tissues and determine the phenotype. Ethylene is primarily involved in flowering, sex determination, fruit ripening, and sensescence (rot). Ethylene is a simple organic molecule, C2 H4, which can also be represented as H2C=CH2.
In cannabis, female plants will produce male flowers if not enough ethylene is present, or if too much gibberellic acid is present. The intersex condition is due to a combination of genetic and environemental factors. Some plants will not turn male under the most extreme stress, and some plants, especially stretchy tropical sativas, will turn with no stress at all. It is my belief that the stress of severe inbreeding, compounded over several generations, is responsible for the majority of hermaphrodites in the drug cannabis gene pool (DCG) today.

Reversal: Treating a female plant with STS in order to collect viable female pollen.

Selfing: Applying female pollen to the female from which it was collected. Example : selecting a particular Willie Nelson cutting, reversing it, and putting the pollen back on another clone of the same plant. Applying that pollen to a different Willie cutting, or to another strain altogether, is not selfing.

F0: The parents selected to start a breeding program. Often referred to as P1 and P2, but this is incorrect.

F1: the first cross between two unrelated parents. The F stands for filial, and refers to the fact that all F1 progeny of the same cross are full brothers and sisters to one another.

S1: The first selfed generation. Selfing an S1 produces an S2, etc. Anecdotal evidence from Sam_Skunkman indicates that continued selfing to the S3 and S4 produces plants so weak that they must be handled very carefully, “like kittens” in his words.

R1's (aka Reversed F1's): When feminized pollen is used to pollinate a different female than the pollen donor. R1's will tend to act like a tradional male x female cross, only all female, while S1's appear to have some different properties that are not yet fully understood. Early reports indicatee that S1's are more consistent than R1's on average, but there are many exceptions, and more research is needed.

BC1: The first backcross generation, ie when an F1 or R1 progeny is crossed back to an F0 parent. Backcrossing can increase the influence of either parent, but continued backcrossing is too much inbreeding, according to both DJ Short and Rezdog, and should be used rarely if at all. One or two backcrosses followed by full-sib mating has beena successful strategy for many breeders, including the creator of Northern Lights.

These terms can be combined for shortand pedigrees. A second backross, followed by three generations of sib-mating, may be represented as a BC2-F3 generation.
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