Reversed Backcrossing:)
- Thread starter englishrick
- Start date
wow,,,your way sounds like a grate idea for makin a STUD seedline,,,,,your % are well high
why did Chimera choose to go a differnt way?,,,,,,an why does he say "nothing is achived after X amount of BackCrossing" ??
im confused on what to buy,,,i feel like buying the GA3 capsules , just because it sounds easy
have you figured out STS?......i just need to see it done once , then il be mixin it in a flash next time,,,,,,,,
it reminds me of the first time i did iso oil ,,in a bowl with a coffee filter,,,,,it took me months to get it together, but once i did it ,i could not believe how easy and primative it was
frigin weird thread,eh?,,,,,,,
i feel like ive smoked a book in the last few days,,,
K
kopite
I think when you breed like this you are looking to add something to the selected recurrent parent it might lack something thus the donor parent can provide therefore if you take it to BC6 whatever you wanted to add will of now been lost and you havnt improved the plant
just to recap,,,
has anyone noticed anything ive said to be incorrect
it would be a big help if anyone can point out something ive said witch is incorrect
many thanks..
has anyone noticed anything ive said to be incorrect
it would be a big help if anyone can point out something ive said witch is incorrect
many thanks..
Octavian
Member
just to recap,,,
has anyone noticed anything ive said to be incorrect
it would be a big help if anyone can point out something ive said witch is incorrect
many thanks..
Chimera has categorically stated that the mathematical basis for "cubing" or multiple backcrosses to a single parent is far too simple a model for any remotely practical use in plant breeding. The recombination of multiple alleles to form the offspring simply does NOT conform to the 1'st gen backcross being 50/50 mother and father, and 2'nd gen backcross will be 75% mother and 25% father, etc...
Search for "chimera myth cubing", you'll get the whole scoop.
Also, multiple generations of inbreeding at the level you are talking about...a single individual, would most likely result in serious problems. I would guess extreme lack of vigor, and increasing percentages of sterile seeds and pollen as lethal alleles accumulate due to the extreme bottlenecking lack of genetic diversity.
FWIW, only pot growers talk about plant breeding with individual plants. In the commercial world of legal genetics, inbred lines are created within a population, not from single plant.
Octavian
dkmonk
Member
Well this thread becomes more interesting the more i click on it. I like your diagrams they help explain a lot.
So your taking this to the s9 then crossing that to make your actual first f1 ?
I hope you can isolate the stink in there, but there are also 80 skunk 1 clones that arent cheese that you could outcross to i bet, even though it seems like you dont want to outcross at all.
Hope this project gets started soon cant wait to see the results, you may revolutionaze a new way of breeding, big props to you for this idea.
So your taking this to the s9 then crossing that to make your actual first f1 ?
I hope you can isolate the stink in there, but there are also 80 skunk 1 clones that arent cheese that you could outcross to i bet, even though it seems like you dont want to outcross at all.
Hope this project gets started soon cant wait to see the results, you may revolutionaze a new way of breeding, big props to you for this idea.
Hello Octavian,
It is funny how folks can read the same exact same thing, or get the exact same dirt under their fingernails, and take away vastly differing conclusions, is it not?
The practicality of cubing depends almost entirely upon the genetics of the recurrent parent.
Inbreeding depression is conceded, what also needs to be conceded is that breeders use this technique anyway and for very good reason, we (some of us at least) have come quite a ways since Darwins "nature abhors self-fertilization". Very much will depend not only on selection, but the original source of the material being worked. If a previously open pollinated line is selfed, chances are many deleterious recessives have been sheltered in heterozygotes and will rise to the surface in early generations of selfing. A line such as Skunk1 on the other hand, one would think many of these would have been previously weeded from the population, and is over that hump so to speak.
In my opinion, bottlenecking is bad only when crap pours out the neck. When nothing is left but outstanding plants, then this is advancement under selection.
It seems to me quite the contrary as well - indeed many pot growers are the only folks having a problem talking about and taking advantage of selfing in breeding.
I will leave you now with a cut and paste from Robert W. Allards "Principles of Plant Breeding", FWIW, in the hope that you might consider altering -at least somewhat- future comments on the subject of what goes down in the commercial world of legal genetics.
" the most useful measure of homozygosity is the inbreeding coefficient, F. This coefficient takes a value near zero in most large random-mating populations, and the coefficient increases toward unity under sustained genetic assortive mating. Self-fertilization (one individual in each generation in each family) leads to very rapid increases in homozygosity. Starting with a heterozygote (F=0.50), F takes the values 0.75, 0.875, 0.9375, 0.9688, 0.9844, 0.9922, ... in successive generations of selfing, thus exceeding 0.90 in the third generation. Under continued mating of 2 individuals per family (full sibs) each generation, F is not expected to exceed 0.90 until the eighth generation. With continued mating of 4 individuals per family (double first cousins), F is not expected to exceed 0.90 until the seventeenth generation and rates of increase in F with 8 individuals per family (quadruple second cousins) and 16 individuals per family (octuple third cousins) are much slower yet. The rate of increase in F is so slow with more than 16 mating individuals per family per generation that such matings are of essentially no consequence in concentrating favorable alleles in selection programs in outcrossing species. It is therefore not at all surprising that breeders of plant species nearly always choose schemes featuring very close inbreeding. Selfing schemes (one parent/generation) are by far the most common in breeding outcrossing plants, and the usual goal is to develop numerous highly homozygous lines that are first evaluated by top crossing to identify lines with good general combining ability, followed by testing specific combinations of pairs of lines to identify the very few pairs that have the potential to produce truly excellent single-cross hybrids. "
amoril
Member
Thats a great quote, Colina, and I think it sums up 1/2 of the task quite well.
It makes no mention of how rigorous a breeder/grower must be in the selection process to achieve the "desired" homogeneity.
what I would imagine, would be the first few generations could be impressively difficult. Recombination can and will be a thorn in the side, IMO. But, as you narrow the genome down, you may end up battling genetic abnormalities, making selection rather easy....the gems will stand out like a beacon.
Either way, the real question for englishrick is, is this feasible? The selection process, that is. Will you be able to grow out enough plants to find the genome youre desiring? Chances are, the s1 generation will be quite the mixed bag of hidden characteristics. s2 may not be substantially better..... Can you grow hundreds of plants per selection? If so, then this could potentially be an avenue to pursue. If not, then how will you tackle it?
K
kopite
Here's an unrelated question along the same lines, (Hope you don't mind Rick).
Would we see the same F1 hybrid vigour in a DCxPetrolia Headstash as we would a DCxHaze? Can lines of genes that are related be recombined to produce vigour in the same way that unrelated lines can?
Would we see the same F1 hybrid vigour in a DCxPetrolia Headstash as we would a DCxHaze? Can lines of genes that are related be recombined to produce vigour in the same way that unrelated lines can?
i thik YES....but the amount of vigor is relative to how distinctly different the 2 parents are geneticly,,,,,,"every indervidual in S1 seedlines is highly geneticly different",,,,this can be a perfect point to create "parralell lines",,in order to increese hybrid vigor at a larer stage,,,,,
depreshion and genetic drift will happen and crossing parralel lines is the only way to increese hybrid vigor while still maintaining homogenous geanes in the progrecy
depending on how different the parralel lines are the seeds are classed as F1
the recombination that happens in F1 seeds "flatlines" the genetic divercity and inderviduals seem very similar".....test crossing combinations of parents while making F1 seelines can lead to results that are so easy to judge you could name the F1 an call it a day
related lines can be combined to produce more vigor in progrency than ither parent......the amount of vigor is determined by the selection of inderviduals as parents,,,,,
i believe that selecting inderviduals will be my only problem with "selfing",,,,my methods of identification are nothing short of "crude".....i wish i had some sort of machine or microscope + identfication info......documenting all info might lead to a relative mathamatical equashion that simplifies this whole thing..
an yes the selection of S1 and S2 plants will be the vital point,,,the inital selection of "reduced genome" in the S1 line, will determine the overall outcome,,,,,,,,,,,,,i need to be very carefull selecting S1 plants to "Self again",,,,
i think sams results show things becoming Homogeneous at S3,,,thats why his plants looked crappy,,,,crossing his S3 to a parralell line might have changed his mind about the whole thing,,,,increesing hybrid vigor and thus showing the true fruits of his labor of love
"i wish i had a better methods of identification ,,",,,i feel silly using my eyes and nose
The latter part of the quoted text seems to speak to the conclusions and direction breeders most often choose based on those conclusions. Do you think they are not taking all of the known considerations into account before choosing direction? Do you feel that they cherry-pick singular arguments and form breeding plans around those?
