how many back crosses before stabilization?
How many back crosses before a person can make the claim that they have a unique strain? It seems as if people do one cross and call the offspring some random name. Have I lost faith or what?
how many back crosses before stabilization?
How many back crosses before a person can make the claim that they have a unique strain? It seems as if people do one cross and call the offspring some random name. Have I lost faith or what?
Here's something by Chimera I take everyone knows who he is and I don't have to go into detail It's very interesting and informative so spark one up or hit a bong and read on.
Cubing.......a myth.
Here's breeder chimera's take on the subject:
"you’ve just discovered the biggest myth (IMNSHO) of marijuana breeding- it is a mistake that almost EVERYONE makes (including many of the most respected breeders!).
Backcrossing will not stabilize a strain at all- it is a technique that SHOULD be used to reinforce or stabilize a particular trait, but not all of them.
For e.g.- G13 is a clone, which I would bet my life on is not true breeding for every, or even most traits- this means that it is heterozygous for these traits- it has two alleles (different versions of a gene). No matter how many times you backcross to it, it will always donate either of the two alleles to the offspring. This problem can be compounded by the fact that the original male used in the cross (in this case hashplant) may have donated a third allele to the pool- kinda makes things even more difficult!
So what does backcrossing do?
It creates a population that has a great deal of the same genes as the mother clone. From this population, if enough plants are grown, individuals can be chosen that have all the same traits as the mother, for use in creating offspring that are similar (the same maybe) as the original clone.
Another problem that can arise is this- there are three possibilities for the expression of a monogenic (controlled by one gene pair) trait.
We have dominant, recessive, and co-dominant conditions.
In the dominant condition, genotypically AA or Aa, the plants of these genotypes will look the same (will have the same phenotype, for that trait).
Recessive- aa will have a phenotype
Co-dominant- Aa- these plants will look different from the AA and the aa.
A perfect example of this is the AB blood types in humans:
Type A blood is either AA or AO
Type B blood is either BB or BO
Type AB blood is ONLY AB
Type O blood is OO.
In this case there are three alleles (notated A, B, and O respectively).
If the clone has a trait controlled by a co-dominant relationship- i.e. the clone is Aa (AB in the blood example) we will never have ALL plants showing the trait- here is why:
Suppose the clone mother is Aa- the simplest possibility is that the dad used contributes one of his alleles,
let us say A. That mean the boy being use for the first backcross is either AA or Aa. We therefore have two possibilities:
1) If he is AA- we have AA X Aa- 50% of the offspring are AA, 50% are Aa. (you can do the punnett square to prove this to yourself).
In this case only 50% of the offspring show the desired phenotype (Aa genotype)!
2) If the boy being used is Aa- we have Aa X Aa (again do the punnett square) this gives a typical F2 type segregation- 25% AA, 50% Aa, and 25% aa.
This shows that a co-dominant trait can ONLY have 50% of the offspring showing the desired trait (Aa genotype) in a backcross.
If the phenotype is controlled by a dominant condition- see example #1- all 100% show the desired phenotype, but only 50% will breed true for it.
If the phenotype is controlled by a recessive condition- see example #2- only 25% will show the desired phenotype, however if used for breeding these will all breed true if mated to another aa individual.
Now- if the original dad (hashplant) donates an 'a' allele, we only have the possibilities that the offspring, from which the backcross boy will be chosen, will be either Aa or aa.
For the Aa boy, see #2.
For the aa boy (an example of a test cross, aa X Aa) we will have:
50% aa offspring (desired phenotype), and 50% Aa offspring.
Do you see what is happening here? Using this method of crossing to an Aa clone mother, we can NEVER have ALL the offspring showing the desired phenotype! Never! Never ever ever! Never!! LOL
The ONLY WAY to have all the offspring show a Aa phenotype is to cross an AA individual with an aa individual- all of the offspring from this union will be the desired phenotype, with an Aa genotype.
Now, all of that was for a Aa genotype for the desired phenotype. It isn't this complicated if the trait is AA or aa. I hope this causes every one to re-evaluate the importance of multiple backcrosses- it just doesn't work to stabilize the trait!
Also- that was all for a monogenic trait! What if the trait is controlled by a polygenic interaction or an epistatic interaction- it gets EVEN MORE complicated? AARRGH!!!!
Really, there is no need to do more than 1 backcross. From this one single backcross, as long as we know what we are doing, and grow out enough plants to find the right genotypes, we can succeed at the goal of eventually stabilizing most, if not all of the desired traits.
The confusion arises because we don't think about the underlying biological causes of these situations- to really understand this; we all need to understand meiosis.
We think of math-e.g. 50% G13, 50% hashplant
Next generation 50% G13 x 50% g13hp or (25% G13, 25%HP)
We interpret this as an additive property:
50% G13 + 25% G13 +25% HP = 75% G13 and 25% hashplant
This is unfortunately completely false- the same theory will apply for the so called 87.%% G13 12.5% HP next generation, and the following 93.25% G13, 6.25% HP generation; we'd like it to be true as it would make stabilizing traits fairly simple, but it JUST DOESN'T work that way. The above is based on a mathematical model, which seems to make sense- but it doesn't- we ignore the biological foundation that is really at play.
I hope this was clear, I know it can get confusing, and I may not have explained it well enough- sorry if that is the case, I'll try to clear up any questions or mistakes I may have made.
Have fun everyone while making your truebreeding varieties, but just remember that cubing (successive backcrosses) is not the way to do it!
-Chimera"
Renagade4-20 (05-03-10), TOC HPS (21-04-10)
Confusing stuff!
Unique strain? I don't think there is such a thing. You can think up an exotic mix of strains but it stands to reason that someone somewhere in the world has already bred, back-crossed and named it. I like to create new cross strains from strains that i am growing, i give them a simple name that reflects the strains crossed, ie: Sweet Purple x White Satin = Purple Satin. All of the top breeders worldwide are doing exactly the same, only on a much bigger scale with far better equipment and probably better genetics too, so i don't see why any of us shouldn't do exactly the same and do some experimenting of our own.
There are seed banks around who still stock 'old school original' strains, so that the 'traditional' among us can still get our fix, but for me variety is the spice of life, and whether bred by Dave In Dudley or by some master grower in Holland, the more the merrier.
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BURNZ, thats very interesting mate, altho it all went over my head, trying to figure out the ''big'' words was interesting enough for me . basically then for example, if i was to pollinate a blueberry female with a white widow male, it is entirley possible that these new seeds will only show white widow or blueberry traits and the mother/fathers genes will not come into play?but on the other hand it can show a combo of each. so even if i crossed these two together i could still end up with a white widow or a blueberry or a combination of both?
Bubblegum 12/12 from seed DIARY
From Norn Iron? Then Join The Norn Iron Club
Grow With CFL? Then Join The CFL Squad
Yes that's basically it mate.
As with all living things, it's impossible to say for sure what the offspring will be like or who it 'resembles'.
A man and a woman for instance, if they have a child... a girl say, she could mostly resemble the mother in looks and stature but might have the fathers eyes or nose etc or visa versa. She could also resemble the mother in some ways, the father in others, yet still have her own unique attributes which may come from a mix of genes or indeed from her ancestors.
That is why breeders back-cross, to try and get the best traits (for them) from each individual parent. It is purely random as to what traits will be passed from mother to daughter (seed), which is why some strains need to be back-crossed lots of times in the hope of finding the required trait.
Unfortunately at present it's not possible to say for sure what plant you will get from a set of parents.
But that's nature!
BURNZ (06-03-10), M_C (06-03-10), Renagade4-20 (05-03-10)
thanks grub im gonna have to go do some more research as i was hoping to cross a bubblegum with a blueberry and then pollinate the resulting cross with an ak47. but now it seems that i could be doing all this in vain and id be better suited doing it when i have enough room to grow out a few of each plant to get the best traits and not just 1 of each. thanks again guys
Give it a whirl mate....as the great Mr Gump once said, "you never know what you're gonna get"
cheers for the encouragement i shall undertake this in the future, sooner rather than later i hope
Thanks grub, that brings it down to a level of understanding for most
It's Not What You Know, It's What You Can Prove
Grub (06-03-10)
brings me back to gcse biology alleles and aa and stuff
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