If I understand correctly, a back cross (BX) is when you take a child plant and breed it back to one of the original parents. Often the original parent is a mother plant or a clone of the mother and the child is a male F1 (from the mother and some other plant).
I don’t have this option (the original mother was harvested), so I plan to breed a male child plant (F1) back to his “aunt” (a female “sister” plant to his mother).
Can I rightly call this a “back cross”, or is there some other name for it?
To put it in context:
I bred a male Critical Kush to a female CBDream and got plenty of F1 seeds.
I am growing a new CBDream female (from the same stock of seeds as the first female) and some of the F1 seeds.
I would like to breed an F1 male (if I get one) to this new CBDream female.
The result will be a poly-hybrid. A back cross must involve one of the original parents.
If you can identify a “sister” of the original mother that carries a lot of the same traits, you may get something akin to what you seek, but that is best case scenario.
In fact the backrossing concept can be applied to a wide panel of cases, not only with the direct parents. You can BX the generation F3 to the generation F1, the generation F4 to the initial P1 etc …
On the phenotype side, it concern the whole generation also. Let’s say than you select 4 specimens from the same seed batch
:
F2 White Widow Male 1 X F2 White Widow Female 2 = F3 Offspring #12
F2 White Widow Male 3 x F2 White Widow Female 6 = F3 Offspring #36
If you cross one male #36 F3 to the White Widow Female 2, it’s a BX.
If you cross one female #12 F3 to the White Widow Male 1, it’s a BX.
I would like to breed an F1 male (if I get one) to this new CBDream female.
It’s a BX.
Genetically we can eventually say that if the twos sisters are drastically different, but in sequencing the genes only.
On the sight of the usual “ganja farmer” it will be more used when different lines are concerned.
For the purposes of back crossing to the original mother or father, there is no actual substitute.
Yes the back cross technique can be used. The results will not be driving toward the original mother or father plant, unless that plant is used in the process. Not the same.
A backcross can be considered whatever you use at the moment it’s from the same inbred line. It’s simply the act of crossing a generation with a previous one. The specimens in game doesn’t matter in the qualification, it doesn’t change the horticultural definition. It exist multiple strategies possible around this method than can be debated for sure, but what will do cogitech is a BX by definition.
For the polyhybridism, we are entering in genetic engineering more than in cannabis breeding. I don’t think than in the case of cogitech (or in my tents) it’s contextual. It’s why it’s necessary to sequence the both specimens to be able to state about a polyhybridism of a line. To be qualified, the allelic segregation must be a true genetical shock. Not a simple variation.
I’m not going for perfection/isolation of specific traits of the original mother, and I understand that this is often the whole point of back-crossing. I’m just messing around, really.
My only goal is to pull more of the “CBDream genes” forward into the next generation, and there wasn’t anything that I specifically liked or disliked about the original mother. In fact, she’s the only one I grew.
So, I figure an “aunt” CBDream plant will be carrying her own combination of “CBDream genes” and therefore the “BX1” offspring will essentially be 75% CBDream. BX2 should be 87.5% CBDream, and BX3 should be 93.75% CBDream.
Ideally, I would grow enough of each generation to test for CBD and select good keepers for breeding. Pipe dream…
(The original Critical Kush father apparently had a moderate dose of CBD, so I hope that works in my favour)
I think IMO you will still achieve mostly the same thing
if you are looking to tighten up the genepool to be more representative of the mothers genes
the sister is the closest you can get without having the mother
they probably share 75+% genes
Cannabis specimens are diploids (210). But reproduce by haploids gametes(110). It give :
male 210 → 110 → cross (2*10) ← 110 ← 210 female
As you see, on the global 410 only 25% of the information is really treated by shot. And this 25% will be partially activated with the other 25% to make an unique 210 ID (phenotype).
A lot of people fail theyr BX in thinking than they stack the wanted information at each pass; in fact they mostly are “washing” the others informations by repetition. In considering that, it change a lot the strategy to adopt when you select the offspring to be backcrossed. Because in function of the desired trait statut, the repetition can destruct or reinforce the wanted phenotype generation, make it more latent or more expressed etc … yeah headaches when you want just play around.
There is a simple methodologic trick when you just want to have fun : at each pass choose twos opposite specimens from offspring and use both on your female’s reference. In keeping the lines separated during all the process.
Lets say than the critical kush will split in twos main phenotypes expressions in the hybrid (it’s an example, i suppose it’s critical mass x kush only lol) :
big bud shape / kush buds (#1): elongated thin secondaries with ping pong balls than smell the backwood
kush shape / big bud buds (#2): short internoded specimens with thick secondaries than produce very sweet-sugared buds
Both expression blended with your CBD dream (so than tend naturally to be more kushy-reinforced by the repetition in the example).
You take the pheno #1 and make the line BX1#1; in successive offspring you will take only the BBshape/K-buds phenotypes to choose your specimen to BX and kill all others.
You take the pheno #2 and make the line BX1#2; in successive offspring you will take only the Kshape/BB-buds phenotypes to choose your specimen to BX and kill all others.
This way, you’re insured to isolate twos forms of reinforced expressions during a fews generations and when these ones will produce too much rants / mutants in offspring, just hybridize them and continue again.
I don’t insure you than this way the CBDream phenotype will become homozygotte/stabilized, but at least it will reduce drastically the failures and for sure will lead the chemotype on a CBD balance.
Keep in mind than it’s just a more interresting manner to produce weed, don’t make it a nightmare. If ever you want to push more and set a more advanced process, the documentation is very exhaustive in this subject and used since centuries.
Thanks for all of that. I think I understand most of it. Some day I will read Greg Green’s book (as a start) but I am juggling a lot of things in my life. For now I will “roll the dice” and have some fun, and maybe Lady Luck will pay a visit.
