a little help people on what a Backcross actually is?

[ClearBarbedFunk]

havein a little conversation with another grower, and were not on the same page on what a BX is.

in my mind a BX is goin from one gen to a previous gen, be it one target plant, or the whole generation.

so what im sayin is, you could do the 1st bx between say the F1 and F3, and it shouldnt matter how many plants u use in the BX, it could be 50 from both generations. or one plant in the F1 and 10 in the F3.

as for a BX2, you could do it between the F5 and say F8, that would be the 2cd bx of the lline. and so on, you could waitill the F16 and go back to the F1 and it would still be the 3rd BX, you dont have to do um consecutively.

nor do they have to all go back to a single clone.

someone school me please if im totally in the dark

CBF

 

[Colina]

You are correct sir. Except the second/third backcrosses in your example would not be between f5 and say f8, those parental plants (or group of plants) would either be labeled B1f5 or B1f8 etc back to the recurrent parent/s or line/s, to come to BC2. B2f16 back to A to get BC3 etc.

Here are two examples of how one may come to a BC3.


Example 1:

step 1) A X B = F1

step 2) A X F1 = BC1

step 3) A X BC1 = BC2

step 4) A X BC2 = BC3 (<-- Souls "cube")


Example 2:

step 1) A X B = F1

step 2) A X F1 = BC1 (if we went A X F2 the progeny is still a BC1)

step 3) BC1 X BC1 = B1F2

step 4) A X B1F2 = BC2

step 5) BC2 X BC2 = B2F2

step 6) B2F2 X B2F2 = B2F3

step 7) B2F3 X B2F3 = B2F4

step 8) A X B2F4 = BC3


All of these may be a single plant or group of plants. To further broaden it, A (the recurrent parent) might even be and is often a group of closely related lines.

 

[ClearBarbedFunk]

so for it to be labled a backcross you have to go back to the recurrent parent/group in the BX1 each time for it to be labled BX2 BX3 BX4 and so on.

i was thinkin you didnt have to go back to the plant/group in the first BX, in order to do the BX2. i was under the impression that if i had already done a BX1 in the seedline, i could do another BX further along in the line breeding, not usin the plants in the first BX, and it would still be a BX2 in the seedlines breeding.

for it to be a cube, yes you need to hit the target plant each time you go back. but in linebreeding i didnt think that had to happen.

CBF

 

[ClearBarbedFunk]

whata mess

 

[ClearBarbedFunk]

Example 2:

step 1) A X B = F1

step 2) A X F1 = BC1

step 3) BC1 X BC1 = B1F2

step 4) B1F2 X B1F2=B1F3

step 5) B1F3 X B1F3 = B1F4

step 6) BC1 X B1F4 = BC2

maybe this helps to what im tryin to say

CBF

 

[Colina]

Ah, I see where this is heading.

step 6) BC1 X B1F4 = BC2

I think the progeny of this BC1 X B1F4 may be more properly labeled as B1F5, though not absolutely positive. The BC1 is certainly a closely related line to the original recurrent parent (A), however if the BC1 was not specifically represented in the original group of A (the recurrent parent) then B1F5 may be more correct. You could say BC1 is the now the recurrent parent (A) in a new program and that A (BC1) X B1F4 = BC1. Yes yes, whata mess, I am not certain of the exact denotation in this instance. Your BC1 X B1F4 = BC2 may in fact be perfectly acceptable CBF. Yeah, I know, a lotta help I turned out to be, lol.

 

[ClearBarbedFunk]

yeah i dont know myself for sure, cant seem to find anything written on it specifically.

point im tryin to get my head wrapped around is in order for it to be called a BX2 or 3 or 4 is must you always go back to the plant /group you did the BX1 in.

im thinkin no, seems you could BX at any point in line breeding, as you develope a seedline. i dont see how you could do 4 BXs durin the developement of a seedline and have um all be BX1 F whatever? if ya did 4 BXs durin the work, there were 4 BXs done, your 4th BX at whatever gen is still the 4th time you went back in the work.

if ya did 5 filial gens and 4 BXs, you could say the line is at F9. even though the BX is not a filial gen really, it would count as a generation. least thats my understandin. i may be way off as well, hence the thread.

so in most cases, if you didnt go back to the original target plant (A) its not a BX2 and so on.

CBF

 

[kopite]

FYI CBF,

Wow that is painful for me to read.... I must have been pretty stoned when I wrote that, now years ago. I'm glad at least that it's info that has spread a little knowledge and perspective into the community over the years.. I do however need to re-write it...

Here's a snipet on backcrossing from the breeding chapter I wrote for Jorge's most recent version of the bible.

Backcross Breeding –
A type of breeding that involves repeated crossing of progeny with one of the original parental genotypes; cannabis breeders most often cross progeny to the mother plant. This parent is known as the recurrent parent. The non-recurrent parent is called the donor parent. More widely, any time a generation is crossed to a previous generation, it is a form of backcross breeding. Backcross breeding has become one of the staple methods clandestine cannabis breeders use, mainly because it is a simple, rapid method when using greenhouses or grow
rooms, and requires only small populations. The principle goal of backcross breeding is to create a population of individuals derived mainly from the genetics of one single parent (the recurrent parent).

The donor parent is chosen based on a trait of interest that the recurrent parent lacks; the idea is to introgress this trait into the backcross population, such that the new population is comprised mainly of genetics from the recurrent parent, but also contains the genes responsible for the trait of interest from the donor parent.

The backcross method is a suitable scheme for adding new desirable traits to a mostly ideal, relatively true-breeding genotype. When embarking on a backcross breeding plan, the recurrent parent should be a highly acceptable or nearly ideal genotype (for example, an existing commercial cultivar or inbred line). The ideal traits considered for introgression into the new seed line should be simply inherited and easily scored for phenotype. The best donor parent must possess the desired trait, but should not be seriously deficient in other traits. Backcross line production is repeatable, if the same parents are used.

Backcross breeding is best used when adding simply inherited dominant traits that can easily be identified in the progeny of each generation (example 1). Recessive traits are more difficult to select for in backcross breeding, since their expression is masked by dominance in each backcross to the recurrent parent. An additional round of open pollination or sib-mating is needed after each backcross generation, to expose homozygous-recessive plants. Individuals showing the recessive condition are selected from F2 segregating generations and backcrossed to the recurrent parent (see example 2).

Example 1– Backcrossing: Incorporating a dominant trait

Step1– Recurrent Parent × Donor Parent
|
V
F1 Hybrid generation

Step 2 – Select desirable plants showing dominant trait, and hybridize selected plants to recurrent parent. The generation produced is denoted BC1 (some cannabis breeders break from botanical convention and denote this generation Bx1. BC1= Bx1).

Step 3 – Select plants from BC1 and hybridize with the recurrent parent; the resulting generation is denoted BC2.

Step 4 – Select plants from BC2 and hybridize with the recurrent parent; the resulting generation is denoted BC3.
.

Example 2 Backcrossing: Incorporating a recessive trait

Step1– Recurrent Parent × Donor Parent
|
V
F1 Hybrid generation

Step 2 – Select desirable plants, and create an F2 population via full sib-mating.

Step 3 – Select plants showing the desired recessive trait in the F2 generation, then hybridize selected F2-recessive plants to the recurrent parent. The generation produced is denoted BC1.

Step 3 – Select plants from BC1, and create a generation of F2 plants via sib-mating; the resulting generation can be denoted BC1F2

Step 4 – Select desirable BC1F2 plants showing the recessive condition, and hybridize with the recurrent parent; the resulting generation is denoted BC2.

Step 5 – Select plants from BC2, and create an F2 population via sib-mating; denote the resulting generation BC2F2.

Step 6 – Select plants showing the recessive condition from the BC2F2 generation, and hybridize to the recurrent parent; the resulting generation is denoted BC3.

Step 7 – Grow out BC3, select and sib-mate the most ideal candidates to create an F2 population, where plants showing the recessive condition are then selected and used as a basis for a new inbred, or open-pollinated seed line.

This new generation created from the F2 is a population that consists of, on average, ~93.7% of genes from the recurrent parent, and only ~6.3% of genes leftover from the donor parent. Most importantly, one should note that since only homozygous-recessives were chosen for mating in the BC3F2 generation, the entire resulting BC3F3 generation is homozygous for the recessive trait, and breeds true for this recessive trait. Our new population meets our breeding objective. It is a population derived mainly from the genetics of the recurrent parent, yet breeds true for our introgressed recessive trait.


Backcross derived lines are expected to be well-adapted to the environment in which they will be grown, which is another reason backcrossing is often used by cannabis breeders who operate indoors. Indoor grow rooms are easily replicated all over the world, so the grower is able to grow the plants in a similar environment in which they were bred. Progeny therefore need less extensive field-testing by the breeder across a wide range of environments.

If two or more characters are to be introgressed into a new seed line, these would usually be tracked in separate backcross programs, and the individual products would be combined in a final set of crosses after the new populations have been created by backcrossing.

The backcross scheme has specific drawbacks, however. When the recurrent parent is not very true-breeding, the resulting backcross generations segregate, and many of the traits deemed desirable to the line fail to be reproduced reliably. Another limitation of the backcross is that the “improved” variety differs only slightly from the recurrent parent (e.g., one trait). If multiple traits are to be introgressed into the new population, other techniques such as inbreeding or recurrent selection may be more rewarding.

Hope that's a little more clear......
Respectfully,
-Chimera

I've also tried to add a file FYI.....

http://www.knowledgebank.irri.org/ricebreedingcourse/Powerpoints/MAS_case_study.ppt

I will try add more etc tomorrow as only have limited internet access.....

I only look at Bx with "elite" clones or if a trait needs fixing etc its not something I'm up on so enjoying both your post colina and CBF.....

Kopite

 

[ClearBarbedFunk]

thank you for that bro, as this piece here answers my question....

"More widely, any time a generation is crossed to a previous generation, it is a form of backcross breeding."

seems that most peeps are stuck on the standard bros grimm cube example as far as backcrossing goes.

i had talked often with a cattle breeder here, and pretty much were i came across what i believe to be backcross breeding or what backcrossin actually encompasses.

CBF

 

[Colina]

I downloaded powerpoint viewer but still for some reason am having troubles opening the link you posted Kopite. For certain, more discussion on backcross breeding would benefit the community.

I think more important than exact proper denotation, is being able to answer to myself the whys and where to next in these types of programs. If the recurrent parent breeds true for desired traits, then Souls cube becomes a strong option in reproducing the recurrent parents (say an elite clone) traits in a seedline. Most often in backcross breeding, the recurrent parent is a true breeding line of high overall worth lacking in some inherited qualitys the breeder would like to incorporate (see Chimera's above example)- this is not usually the case for us hacks trying to forge a seedline out of a single resin bomb.

I remember Chimera I think said that it may be best to simply save the clone line via BC1, and then select/inbreed from there. I am certainly not Chimera and am somewhat outclassed there, but I assume this comment was because he knows that the vast majority of clones in fact do not breed true - and therefore a number of backcrosses to it is pretty much wheel spinning. Where as if the recurrent parent did breed true it would be a different story.

Not breeding true seems problematic with a recurrent parent, or we may have a hermie problem with a recurrent parent as well. The best option may be to not use these types of plants as recurrent parents in the first place. No amount of filial inbreeding between backcrosses will solve these problems if we end up crossing back to the problem again.

 

[Pops]

I think you have hit the nail on the head, Colina. The recurrent parent or original breeding mom may have some fantastic traits(truebreeding or not) that you want to express, but may also have a deleterious true breeding trait(like hermi prone) that you wish to eliminate. By back crossing to a filial generation that does not contain that deleterious trait, you can improve the line, and hopefully keep the desired traits. I remember that Chimera did not seem to be a fan of Souls cube method. It seems that soul was focusing primarily on potency, which made it a little easier. With selection of multiple desireable traits, there is going to have to be a whole lot of breeding going on if the traits are not true breeding. Great discussion,folks. I'll be watching this thread.

 

[Colina]

Hiya Pops, very good to see you.

"By back crossing to a filial generation that does not contain that deleterious trait, you can improve the line, and hopefully keep the desired traits."

Yes and if the recurrent parent has undesirable traits, then the final breeding in this case should probably be sib mating, as in Chimeras above example 2, as opposed to backcrossing.

"I remember that Chimera did not seem to be a fan of Souls cube method."

That I am attempting to put forward is because Chimera knows damn well how rare it is to find an elite clone in say an F2 gen of a polyhybrid that breeds true for many traits. Soul seemed to have happened upon one that did, but I believe Chimera felt this too rare to put the cube forward as sound practice in many scenarios. If indeed this was his thought, then I concur. Hi, my name is Selfwell Cubewell - If a clones S1 progeny is desirable as a whole, then the clone is a prime candidate as a recurrent parent in Souls cube.

"It seems that soul was focusing primarily on potency, which made it a little easier."

In my experience potency is a more complex trait/s. I believe it is a group of traits that result in overall potency -ranging from trichome field density to cannabinoid/terpenoid profile etc- definitely not something like Aa. It is complex, like yield, it is many different traits that make up its overall sum.

"With selection of multiple desirable traits, there is going to have to be a whole lot of breeding going on if the traits are not true breeding."

Yes yes, but if these traits do breed true, then backcrossing becomes easy, automatic, and a highly dependable way to incorporate multiple and even very complex traits into a seedline (including complex traits like potency and yield - Selfwell Cubewell). This is both the beauty and the fault of backcross breeding.

Hopefully some others will show up with their thoughts as well.

 

[N. Accumbens]

Heya there folks!
I'm on hole digging duty this spring so I have been off and around.
...but backcrossing is a fave topic of mine...as is any genetics convo.

As we have mentioned in one of my journals backcrossing has its pluses in that a breeder can fairly simply pull out a desired trait (true-breeding) whilst still being able to slightly determine the outcome of any additional traits by adding in some new chosen desired trait and hopefully having the alleles match up "just right".

Colina well points out, negative aspects of such techniques include the expression of any possible unwanted traits such as hermafroditism, a sensitivity to heat, or low tolerance to pests or molds.

Often backcross breeding is more chosen to preserve a desired line...trait...whatever that one thing was that made you fall in love with the chosen fe/male {be we so lucky to have only one trait we desire}

With any breeding program it is important to look at what one has... what one wants... and which methods will be most effective at getting one to their desired goal... the rest is just sweat, sawdust, and research.

"If the recurrent parent breeds true for desired traits, then Souls cube becomes a strong option in reproducing the recurrent parents (say an elite clone) traits in a seedline."

"[...] the case for hacks trying to forge a seedline out of a single resin bomb."

Well said...

'nuff said!


Time to make the hillsides look like swiss cheese again... but i am sure to be lurking behind a nice big canna bush somewhere...
BE well all...
NAcc

Take it cheesy...

 

[kopite]

I downloaded powerpoint viewer but still for some reason am having troubles opening the link you posted Kopite. For certain, more discussion on backcross breeding would benefit the community.

it should work, its ok for me... its basically a look at marker assisted backcrosiing within rice populations, where they have a "mega" plant as they call it... and how quick its to achieve the same results, much quicker than conventional Backcrossing...

I've read that tomatoe breeders are using MAB as they find certain tomatoes that are completely resistant to powdry mildew and therefore want this gene passed on etc....

heres a bit on it, but be warned its probably a headache read.....

http://www.genetics.org/cgi/reprint/170/2/909.pdf

obviously would help if we all had our lab and resources but still food for thought.... (maybe someone has these facilities ???)

That I am attempting to put forward is because Chimera knows damn well how rare it is to find an elite clone in say an F2 gen of a polyhybrid that breeds true for many traits. Soul seemed to have happened upon one that did, but I believe Chimera felt this too rare to put the cube forward as sound practice in many scenarios. If indeed this was his thought, then I concur. Hi, my name is Selfwell Cubewell - If a clones S1 progeny is desirable as a whole, then the clone is a prime candidate as a recurrent parent in Souls cube.

Well put.....

If a clones S1 progeny is desirable as a whole, then the clone is a prime candidate as a recurrent parent in Souls cube

this is were selfing is a valuable tool as to my knowledge when the clone is selfed approx half the loci become homozygous thus we can eliminate deleterious alleles, I hope I'm right in thinking when we produce a selfed population we produce double haploids ? someone tell me if i'm wrong....

below is a look at this with Cassava.....

http://cgiarfinanceinfo.org/asia_cassava/pdf/proceedings_workshop_02/150.pdf

obviously for me this is all theory... I have limited practical knowledge of backcrossing

Kopite

 

[Colina]

Indeed a headache read for me Kopite. I am fairly comfortable with my farmer judo in some areas and am always endeavoring to improve but a lot of that tech-math is still full-on gibberish to me unfortunately.

But I'm pretty sure that double haploids are created in the lab by doubling the genetic material (creating a homozygous condition in some number of the population) via various frankenstein type breeding techniques. Please don't let this get around though, the granola anti-selfing crowd might have a hissy-fit to learn about some of the techniques used in breeding the things found down at their local organic food store

Selfing is surely a valuable tool. Traits that breed true will continue to be homozygous and heterozygous traits move relatively quickly in the direction of homozygosity under selfing regimens.

 

[kopite]

Indeed a headache read for me Kopite. I am fairly comfortable with my farmer judo in some areas and am always endeavoring to improve but a lot of that tech-math is still full-on gibberish to me unfortunately.

But I'm pretty sure that double haploids are created in the lab by doubling the genetic material (creating a homozygous condition in some number of the population) via various frankenstein type breeding techniques. Please don't let this get around though, the granola anti-selfing crowd might have a hissy-fit to learn about some of the techniques used in breeding the things found down at their local organic food store

Selfing is surely a valuable tool. Traits that breed true will continue to be homozygous and heterozygous traits move relatively quickly in the direction of homozygosity under selfing regimens.

I like my Math or maths....

could you use Colchicine to produce double haploids.... or introduce a strain such as chemo to a breeding scheme...

Kopite

 

[Bass Akwards]

Back to the future ...

Back to the future ...

This method of "stunt breeding" keeps popping up.

If you really want to, go ahead and play Frankenstein.

But remember: Colchicine is just not a reliable tool.

The affected sprouts are very easy to spot, but grow very slowly.

( If they don't just roll over and die. )

Even with lab-grade Colchicine, it's hard to judge the effective dosage.

The resulting plants are very dark colored, and can have other interesting qualities, but they do not breed true. They don't pass on the doubled genes.

Been there & done that decades ago.

Cute idea, but Not worth the trouble.

 

[kopite]

To my knowledge it has been used in sucessful breeding programs for many plants, orchids etc, but still I understand how some see it as Frankestein like !, although you can get it naturally from plants such as meadow saffron (lily fam), anyway I'm not planning on using it soon, prob best to just X-ray the seeds lol... I'll stick to my mutant search.....

Kopite

 

[Bass Akwards]

X-Ray Ahoy!

X-Ray Ahoy!

Having a friendly dentist or hospital tech irradiate a batch of seeds could be big fun. Starting with some research to determine a reasonable base-line, then taking three or four batches of the same seeds and hitting them with ever larger doses. How many rads until they glow in the dark?

This would be far preferable to trying colchicine.

Even with the right dosage, one that produces a large number of swollen, grossly enlarged root tips, ( the sign of polyploid genes ), the sprouts rarely are able to grow much further. A small number can form the first set of leaves, and fewer still will grow a second. They look a lot like runts, and very rarely grow out of it. The few that do aren't any great shakes, aside from the extra dark cosmetics.

A good Gas Chromatography connection would be much more useful to a breeding program than any genetic monkey-business. IMNSHO

 

[kopite]

Having a friendly dentist or hospital tech irradiate a batch of seeds could be big fun. Starting with some research to determine a reasonable base-line, then taking three or four batches of the same seeds and hitting them with ever larger doses. How many rads until they glow in the dark?

This would be far preferable to trying colchicine.

Even with the right dosage, one that produces a large number of swollen, grossly enlarged root tips, ( the sign of polyploid genes ), the sprouts rarely are able to grow much further. A small number can form the first set of leaves, and fewer still will grow a second. They look a lot like runts, and very rarely grow out of it. The few that do aren't any great shakes, aside from the extra dark cosmetics.

A good Gas Chromatography connection would be much more useful to a breeding program than any genetic monkey-business. IMNSHO

Bass,

Have you ever come across people using Glutamine in projects at all ???

Kopite