F1, F2, P1 + how to stabilize your F1s
I ran across this a few days ago and thought i’d share it with those of you who either always wondered or maybe need a refresher course
What really is an F1 cross?
Well defining the terms P1, F1, F2, homozygous, and heterogygous can be a simple task,
however, applying them to applied genetics can often create confusion. Depending on
your point of reference, a plant could be described as any of these terms. For our specific
field of interest it’s important to further define these terms to reduce confusion and protect
the consumers. First I’ll provide the classic scientific definition of these and other related
terms and then I’ll dive into each term into detail.
Heterzygous – a condition when two genes for a trait are not the same on each member of a pair of
homologous chromosomes; individuals heterozygous for a trait are indicated by an “Aa” or “aA” notation
and are not true breeding for that trait.(Clarke)
Homozygous – the condition existing when the genes for a trait are the same on both chromosomes of a
homologous pair; individuals homozygous for a trait are indicated by “AA” or “aa” and are true breeding
for that trait. (Clarke)
– Now the heterozygous and homozygous terms can be applied to one trait or a group of traits within an
individual or a group of individuals. Depending on your point of reference, an individual or group can be
considered both homozygous or heterozygous. For instance, say you have two individuals that are both
short (S) and have webbed leaves (W) and have the following genotypes.
#1 = SSWW
#2 = SSWw
They are both homozygous for the short trait but only individual #1 is homozygous for the webbed leaf
trait. Individual #2 is heterozygous for the webbed leaf trait and would be considered a heterozygous
individual. As a goup, they would be considered heterozygous in general by some and homozygous by
others. It would depend on your point of reference and the overall importance you place on the webbed
leaf trait. Most would consider it to be heterozygous.
For example, the blueberry cannabis strain is considered a true breeding homozygous seed line because
as a whole the many offspring have a similar look and produce a similar product. However there are
often subtle differences between the plants of characters such as stem colour and potency. When taking
a close look at blueberry, you will find heterozygous traits, but because of the whole overall look, we
still generally consider them homozygous for the purpose of breeding programs. Using dogs is another
way to explain this, take a dobie for example, you can tell the difference between dobies, but you can
tell a dobie from another breed. Ya follow?
Hybrid – An individual produced by crossing two parents of different genotypes. Clarke says
that a hybrid is a heterozygous individual resulting from crossing two separate strains.
– For the purpose of seedbanks, a hybrid is in general, a cross between any two unrelated seedlines.
ANY HYBRID IS heterozygous and NOT TRUE BREEDING.
F1 hybrid – is the first generation of a cross between any two unrelated seedlines in the creation of a
hybrid. F1 hybrids can be uniform or variable depending on the P1 parent stock used.
F2 hybrid – is the offspring of a cross between two F1 plants (Clarke).
What Clarke and other sources don’t make clear is do the two F1’s need to be from the same parents? By convention they don’t. As
well, german geneticists often describe a backcross of an F1 back to a P1 parent as a F2 cross.
– OK lets say we take blueberry and cross it with romulan (both relatively true breeding of their unique
traits) to create the F1 hybrid romberry. Now lets cross the F1 romberry with a NL/Haze F1 hybrid.
Some could say this is a F1 cross of romberry and NL/Haze. Others could argue that it is a F2 cross
of two F1 hybrids. Gets confusing doesn’t it? Now lets cross this Romberry/NL/Haze(RNH) with a
Skunk#1/NL#5 F1 hybrid to create RNHSN. Now some would argue that RNHSN is an F1 hybrid
between RNH and SK/NL seedlines. Others would call it an F2.
– So what does this mean to the consumer? It means that a seed bank can call a cross whatever it wants
until the industry adopts some standards. This is what this article will attempt to initiate. Clarke eludes to
standardising these definitions but never really gets around to it. Fortunately other plant breeding
communities have (Colangelli, Grossnickle&Russell, Watts, &Wright) and adopting their standards
makes the most sense and offers the best protection to the seedbank consumer.
Watts defines an F1 as the heterozygous offspring between two homozygous but unrelated seedlines.
This makes sense and gives the F1 generation a unique combination of traits; uniform phenotype but not
true breeding. This is important in the plant breeding world. This means that when a customer buys F1
seeds that they should expect uniform results. It also means that the breeder’s work is protected from
being duplicated by any other means than using the original P1 (true breeding parents). [There are
exceptions to this by using techniques such as repeated backcrosses (cubing the clone)]
F2 crosses are the offspring of crossing two F1 hybrids. This means that they will not be uniform nor
will they breed true. However, F3, F4, F5, etc will also share these characteristics, so to simplify
terminology for the seedbanks and seedbank merchants, they can all be classified as F2 seeds in general.
What does this mean for the preceeding example? Well, the blueberry, romulan, skunk#1, NL#5, and
haze were all P1 true breeding seedlines or strains (another term that needs clarification). Romberry,
NL/Haze, and SK/NL were all F1 hybrids. Both the Romberry/NL/Haze and the RNHSN would be F2s.
Within each group the consumer can know what to expect for the price they are paying.
Few cannabis seedbanks (if any) and their breeders are following these definitions and are subsequently
creating confusion within the cannabis seedbuying community. This is a change that needs to happen.
Note: this is a rough draft to be published to the internet. Hopefully in time it or something similar will be
used to help establish an industry standard. Any comments and critism is welcome to aid in the
production of the final draft. Small steps like this can only benefit the cannabis community over the long
How do you stabilize a strain you crossed?
- Jul 22, 2018
Recently ive cross some Sour Diesel Male x Kings Kush Female,which those would be Parents 1&2.How do i go about stabilizing this cross along the way down to get all my plant look indentical?
- Jul 22, 2018
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