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Quick Course In Cannabis Cross-Breeding & Genetics

Mr. Krip

Grow Journalist
420 Staff
Cannabis Cross-Breeding & Genetics

I tend to monitor the Unanswered Threads so I can assist some of the newer growers, and I recently came across a great question that, frankly, had no short or easy answer and prompted me to post this thread that will hopefully provide some insight into Cannabis Cross-Breeding & Genetics.

First, let me say that I'm not an expert in breeding, but am knowledeable enough to know that actually creating a good, stable, strain of medical cannabis can take years to accomplish and most of us will never be at that level. However, there's no reason we can't all "play" with some breeding as a way to create some new crosses, create our own seeds, preserve some of our favorite genetics, and have fun along the way.

This is NOT a comprehensive guide to breeding, just an overview and explanation of some of the terms.

We're all likely familiar with the two families of Cannabis used for medicinal purposes, including Cannabis Sativa and Cannabis Indica.

Sativas tend to grow taller with narrow, light green leaves and are native to Mexico, Columbia, Africa, Thailand & India. Indicas tend to grow shorter with fat, dark green leaves and they mature quicker and have more resinous flowers than Sativas. Indicas are native to the high northern mountain ranges of the Afghani Hindu Kush, Pakistani Kara Korams, Russian Pamirs and Indian Himalayas.

There are numerous strains of both Sativa and Indica.

A "Hybrid" is created by crossing two DIFFERENT "True-Breeding" strains. A true-breeding strain simply means that the genetics are stabilized so the seeds will carry traits "true" to the strain. A true-breeding strain is either is "Pure-Bred" or a "Stabilized Hybrid".

A Pure-Bred strain is a landrace strain that has only been able to reproduce with other similar strains, so the have almost identical genes.

A Stabilized Hybrid is created by crossing two different strains and then inbreeding the resulting cross for several generations until their traits become stable from generation to generation.

For breeding purposes, the two true-breeding strains to be used as parents are "P1". An “F1” is a seed or plant with two true-breeding parents and is effectively the first generation of the new strain. That being said, a man & woman can have ten children together and some will have brown hair, some will be blond; some will have blue eyes and some brown, some will be tall others short, etc. In other words, while each child can share some of the traits from either parent, it's very difficult to predict the outcome of that F1 generation since it has not been "stabilized".

The breeder will typically take the F1's that express the traits he's after and, by breeding two F1's, an "F2" is created. And, F2's can be bread with other F2's to create F3's, etc. The more generations you bread out, the more difficult it is to predict the resulting genetic traits, and because of this, breeders typically do not go past the F3 generation.

So, what are the odds you can get the qualities you're looking for when cross-breeding?

For F2's, with any specific trait, there's a 50% chance a specific trait will be common to F1, 25% chance it comes from the P1 male and 25% chance it comes from the P1 Female.

However, "Back-Crossing" can significantly improve those odds. When you back-cross F1 with P1, the F2's now have a 50% chance the trait will be from the F1 and 50% chance it will be from the P1 parent it was back-crossed with.

And, it gets even better (albeit, slightly more complicated!) with back-crossing because if you take that F2 back-cross and back-cross it again with P1, one of two things will happen to the F3 generation: either 100% will have the F2 trait OR 100% will have the P1 trait. These are known as an "F3 back-cross squared" and is a great method of ensuring little genetic drift between generations. However, just because you've managed to lock-in the trait you were looking for doesn't mean that other desireable traits weren't lost along the way.

To create an auto-flowering strain, the photo-period plant is crossed with Cannabis Ruderalis. Ruderalis is a low-THC species of Cannabis which is native to Central and Eastern Europe and Russia. Many people consider Ruderalis to be its own species due to its unique traits and phenotypes which distinguish it from Indicas and Sativas, however it is widely debated as to whether or not Ruderalis is actually a sub-species of Sativa.

Ruderalis is a short and stalky plant compared to Sativa and Indica that typically grows to 1 to 2 1/2 feet tall at harvest, with a rugged and shaggy growth pattern that produces wide, light green leaves. The buds from the ruderalis plant tend to be small but still relatively chunky, and are supported by sturdy, thick stems.

What really sets Ruderalis apart is its flowering cycle that is induced according to its maturity instead of being activated by the light schedule, like Indica and Sativa. Modern Ruderalis hybrids usually begin to flower between 21 and 30 days after the seeds have been planted, regardless of the light cycle.

However, this auto-flowering gene is "recessive" so a true photo-period plant crossed with an auto will always produce photos for offspring, BUT they will all have the auto gene. If you cross two of the Auto x Photo crosses, even though they are both photo, because they both have that recessive auto gene, 25% will be auto. If you then cross two of those auto-ing offspring, you'll get 100% auto.

So, getting the photo is easy, but it would take four generations to ensure the auto trait:

1) P1 Generation - One Auto & One Photo
2) F1 - All photo's with auto trait
3) F2 - 25% auto's
4) F3 - Crossing two F2 auto plants ensures auto's for seeds

That's about all I have time for tonight, so I hope this helps answer some questions.

Happy Harvests!

:Namaste:

K
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
I tend to monitor the Unanswered Threads so I can assist some of the newer growers
Thank you!

Many people consider Ruderalis to be its own species due to its unique traits and phenotypes which distinguish it from Indicas and Sativas, however it is widely debated as to whether or not Ruderalis is actually a sub-species of Sativa.
Some people consider ruderalis strains (and, I'd assume hemp strains) to be sativa, and all "drug" strains to be indica, simply(?) referring to those as being either wide- or narrow-leaf strains, depending. There... seems to be some scientific truth to this line of reasoning, actually - although I'm pretty vague on it.

Some people think Cannabis chinensis to be a species, while others consider it to be a sub-species. I don't really remember anything about that line, other than Soma had some of it in his breeding cabinet at one time (IDK whether this is still the case), used it in at least one of his strains (Somana? I think it was...), and that this is why the strain was known for producing tiny budlets at the base of many leaves where the "fingers" (lamina? laminae?) met the petiole. I wouldn't mind stumbling into a few of these seeds.

As you stated, there is still some heavy debate.

Off-topic, probably, but the laws in the US once almost universally referred to Cannabis sativa, specifically. Lots of defense attorneys tried to use "but my client was growing Cannabis indica, which is clearly not mentioned..." as a defense strategy. I don't know if any of them ever won a case this way.
 

newws

Active Member
Cannabis Cross-Breeding & Genetics


That's about all I have time for tonight, so I hope this helps answer some questions.

Happy Harvests!

:Namaste:

K
Wooow man. Thanks a lot!
 
Some people think Cannabis chinensis to be a species, while others consider it to be a sub-species. I don't really remember anything about that line, other than Soma had some of it in his breeding cabinet at one time (IDK whether this is still the case), used it in at least one of his strains (Somana? I think it was...), and that this is why the strain was known for producing tiny budlets at the base of many leaves where the "fingers" (lamina? laminae?) met the petiole. I wouldn't mind stumbling into a few of these seeds.
I was growing the Spanish 'low flyer' from Crop King, there were definitely buds at the stem of each petiole. Tiny, didn't do much - they are dried and ready for infusion!
 

weenmeoff

Photo of the Month: June 2018 - Nug of the Month: November 2018
Cannabis Cross-Breeding & Genetics

I tend to monitor the Unanswered Threads so I can assist some of the newer growers, and I recently came across a great question that, frankly, had no short or easy answer and prompted me to post this thread that will hopefully provide some insight into Cannabis Cross-Breeding & Genetics.

First, let me say that I'm not an expert in breeding, but am knowledeable enough to know that actually creating a good, stable, strain of medical cannabis can take years to accomplish and most of us will never be at that level. However, there's no reason we can't all "play" with some breeding as a way to create some new crosses, create our own seeds, preserve some of our favorite genetics, and have fun along the way.

This is NOT a comprehensive guide to breeding, just an overview and explanation of some of the terms.

We're all likely familiar with the two families of Cannabis used for medicinal purposes, including Cannabis Sativa and Cannabis Indica.

Sativas tend to grow taller with narrow, light green leaves and are native to Mexico, Columbia, Africa, Thailand & India. Indicas tend to grow shorter with fat, dark green leaves and they mature quicker and have more resinous flowers than Sativas. Indicas are native to the high northern mountain ranges of the Afghani Hindu Kush, Pakistani Kara Korams, Russian Pamirs and Indian Himalayas.

There are numerous strains of both Sativa and Indica.

A "Hybrid" is created by crossing two DIFFERENT "True-Breeding" strains. A true-breeding strain simply means that the genetics are stabilized so the seeds will carry traits "true" to the strain. A true-breeding strain is either is "Pure-Bred" or a "Stabilized Hybrid".

A Pure-Bred strain is a landrace strain that has only been able to reproduce with other similar strains, so the have almost identical genes.

A Stabilized Hybrid is created by crossing two different strains and then inbreeding the resulting cross for several generations until their traits become stable from generation to generation.

For breeding purposes, the two true-breeding strains to be used as parents are "P1". An “F1” is a seed or plant with two true-breeding parents and is effectively the first generation of the new strain. That being said, a man & woman can have ten children together and some will have brown hair, some will be blond; some will have blue eyes and some brown, some will be tall others short, etc. In other words, while each child can share some of the traits from either parent, it's very difficult to predict the outcome of that F1 generation since it has not been "stabilized".

The breeder will typically take the F1's that express the traits he's after and, by breeding two F1's, an "F2" is created. And, F2's can be bread with other F2's to create F3's, etc. The more generations you bread out, the more difficult it is to predict the resulting genetic traits, and because of this, breeders typically do not go past the F3 generation.

So, what are the odds you can get the qualities you're looking for when cross-breeding?

For F2's, with any specific trait, there's a 50% chance a specific trait will be common to F1, 25% chance it comes from the P1 male and 25% chance it comes from the P1 Female.

However, "Back-Crossing" can significantly improve those odds. When you back-cross F1 with P1, the F2's now have a 50% chance the trait will be from the F1 and 50% chance it will be from the P1 parent it was back-crossed with.

And, it gets even better (albeit, slightly more complicated!) with back-crossing because if you take that F2 back-cross and back-cross it again with P1, one of two things will happen to the F3 generation: either 100% will have the F2 trait OR 100% will have the P1 trait. These are known as an "F3 back-cross squared" and is a great method of ensuring little genetic drift between generations. However, just because you've managed to lock-in the trait you were looking for doesn't mean that other desireable traits weren't lost along the way.

To create an auto-flowering strain, the photo-period plant is crossed with Cannabis Ruderalis. Ruderalis is a low-THC species of Cannabis which is native to Central and Eastern Europe and Russia. Many people consider Ruderalis to be its own species due to its unique traits and phenotypes which distinguish it from Indicas and Sativas, however it is widely debated as to whether or not Ruderalis is actually a sub-species of Sativa.

Ruderalis is a short and stalky plant compared to Sativa and Indica that typically grows to 1 to 2 1/2 feet tall at harvest, with a rugged and shaggy growth pattern that produces wide, light green leaves. The buds from the ruderalis plant tend to be small but still relatively chunky, and are supported by sturdy, thick stems.

What really sets Ruderalis apart is its flowering cycle that is induced according to its maturity instead of being activated by the light schedule, like Indica and Sativa. Modern Ruderalis hybrids usually begin to flower between 21 and 30 days after the seeds have been planted, regardless of the light cycle.

However, this auto-flowering gene is "recessive" so a true photo-period plant crossed with an auto will always produce photos for offspring, BUT they will all have the auto gene. If you cross two of the Auto x Photo crosses, even though they are both photo, because they both have that recessive auto gene, 25% will be auto. If you then cross two of those auto-ing offspring, you'll get 100% auto.

So, getting the photo is easy, but it would take four generations to ensure the auto trait:

1) P1 Generation - One Auto & One Photo
2) F1 - All photo's with auto trait
3) F2 - 25% auto's
4) F3 - Crossing two F2 auto plants ensures auto's for seeds

That's about all I have time for tonight, so I hope this helps answer some questions.

Happy Harvests!

:Namaste:

K

Thanks Krip! Learned some stuff today! :high-five:
 

HighTechRasta

Well-Known Member
Absolutely incredible information, thank you!

I think the obvious next part of this discussion should be about feminized seed creation
and the use of feminized pollen made with the colloidal silver method.
I'm dying to know if using the silver method on an auto to self pollinate will produce
100% auto seeds or not...

:Rasta:
 

Amy Gardner

Member of the Month: March 2018 - Photo of the Month: April, Dec 2018, Apr 2019

Blazinjones

Well-Known Member
Absolutely incredible information, thank you!

I think the obvious next part of this discussion should be about feminized seed creation
and the use of feminized pollen made with the colloidal silver method.
I'm dying to know if using the silver method on an auto to self pollinate will produce
100% auto seeds or not...

:Rasta:
Well I used colloidal silver to try an reverse a fem auto and the few I kept tryn werent reversing for me. So I went with sts an got a bunch of fem pollen then. Which I dusted on another fem auto an so far all that I've ran an any1 I've seen use em have been autos. An I got a ton of beans so I dnt even know if I'll even run all of them. So I dnt think I'll ever find out if it's a 100% or not lol. But thts how I got my auto bean collection am will be doing an photos this way as well. Hope that helps some.
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
The gene for the autoflowering trait is recessive, so:

Autoflower x autoflower = autoflower.

Autoflower x photoperiodic (with no autoflowering gene) = photoperiodic, with all progeny carrying one gene for the autoflowering trait and one for the photoperiodic gene.

Autoflower x photoperiodic (with one autoflowering gene) = mix.
 

Blazinjones

Well-Known Member
The gene for the autoflowering trait is recessive, so:

Autoflower x autoflower = autoflower.

Autoflower x photoperiodic (with no autoflowering gene) = photoperiodic, with all progeny carrying one gene for the autoflowering trait and one for the photoperiodic gene.

Autoflower x photoperiodic (with one autoflowering gene) = mix.
So if I reversed a pineapple Express auto and used that pollen on a c4 auto fem would those first beans be jus c4 then or would they be a mix of both? Or would I need to cross the new beans I would have made again with one of the parent beans?
 

Mr. Krip

Grow Journalist
420 Staff
So if I reversed a pineapple Express auto and used that pollen on a c4 auto fem would those first beans be jus c4 then or would they be a mix of both? Or would I need to cross the new beans I would have made again with one of the parent beans?
If BOTH parents are auto's, ALL progeny will be autos.
 

Oldgrowth

Well-Known Member
Mr. Krip thank you for the excellent review of basic genetics. I learned this studying inbred mice long ago and those stable principles still apply but I'm bemused by the phenotypic variability of presumed same-strain females that I grow. The landraces I have grown over the years, Hindu Kush and Afghan Kush, have been more consistent with one extreme outlier out of 12, but the hybrids vary quite a bit. This year the distinctions between 3 similarly treated and situated GG4 plants are size/rate of development (12" -> 5") and apparent resistance to insects. The 5" plant I call "Runtie" has numerous bites despite weekly Neeming. Is phenotypic variability a result of seed producers techniques that are questionable or caused by the inevitable way that a plant's treatment may vary from one to another on various subtle factors? My single Afghan Kush this year is tall, dark and beautiful as I imagined she would be from past experience. I grow her for her looks mostly and as a comparison standard. I expect her to go to 7' or so with the GG4 ladies around 5' but gushing sticky promise again.

Peace
 

Mr. Krip

Grow Journalist
420 Staff
Mr. Krip thank you for the excellent review of basic genetics. I learned this studying inbred mice long ago and those stable principles still apply but I'm bemused by the phenotypic variability of presumed same-strain females that I grow. The landraces I have grown over the years, Hindu Kush and Afghan Kush, have been more consistent with one extreme outlier out of 12, but the hybrids vary quite a bit. This year the distinctions between 3 similarly treated and situated GG4 plants are size/rate of development (12" -> 5") and apparent resistance to insects. The 5" plant I call "Runtie" has numerous bites despite weekly Neeming. Is phenotypic variability a result of seed producers techniques that are questionable or caused by the inevitable way that a plant's treatment may vary from one to another on various subtle factors? My single Afghan Kush this year is tall, dark and beautiful as I imagined she would be from past experience. I grow her for her looks mostly and as a comparison standard. I expect her to go to 7' or so with the GG4 ladies around 5' but gushing sticky promise again.

Peace
The wide variability in many of the newer strains are simply due to the fact that those strains haven't been "stabilized" yet, usually because the breeder is in such a rush to get the newest strain on the market as quickly as possible.

This is related to my statement that:

First, let me say that I'm not an expert in breeding, but am knowledeable enough to know that actually creating a good, stable, strain of medical cannabis can take years to accomplish
The goal SHOULD be to give the grower a fairly predictable outcome when he pops a pack of beans with most showing characteristics that are representative of that strain.

Unfortunately, many breeders don't take time to stabilize their strains so you get 5 different phenos in every 5-pack of seeds.

This is the type of variability most of us will get at home when we "play" with crossing our strains. However, by using selective breeding and back-crossing, over time you can lock in a set of traits that will be common to that strain and/or greatly limit the number and variance of phenotypes.
 

Blazinjones

Well-Known Member
Ok I always get alil confused when people say back crossing I mean its technically straight forward. But I was wondering let's say I have 2 fem beans of same strain an i wanted to use it in a cross I made or jus to make more beans. Either way how would I back cross if i only started with the 2 beans? I would need to reverse one an use tht fem pollen to dust the second one an I would then get fem beans. So what would I do then would I jus run some an pick the best 2 I want then cross them. And from that second batch of beans would I cross them with one from the first batch then would that be the back cross?
 

Mr. Krip

Grow Journalist
420 Staff
Ok I always get alil confused when people say back crossing I mean its technically straight forward. But I was wondering let's say I have 2 fem beans of same strain an i wanted to use it in a cross I made or jus to make more beans. Either way how would I back cross if i only started with the 2 beans? I would need to reverse one an use tht fem pollen to dust the second one an I would then get fem beans. So what would I do then would I jus run some an pick the best 2 I want then cross them. And from that second batch of beans would I cross them with one from the first batch then would that be the back cross?
To make it simple, a backcross is the resulting seed from a plant crossed with one of it's earlier generation parents, grandparents, great grandparents, etc.

If the pollen donor is a reversed female, all seeds should be female.
 

Blazinjones

Well-Known Member
Ok I didnt know if it needed to be from the same parent or not to be considered a back cross lol. But yea thanx for clearing that up for me I've jus been trying to save certain seeds I got to either make more beans of tht paticular strain or make a new cross. But either way whatever I do I wana start to improve the strains I make an get them more dialed in an not a 100 different phenos.
 
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