SCARHOLE
Well-Known Member
(Thanks goes out to GreenSupreme for this. Your the man!
)
I found an old disk from before I ripped out my old hard drive and left the country for a year. There is a bunch of usefull info in there, but yes it is VERY long. But hey what do you want from old Brothers Grim and Vic High info, good score I think. Peace
OverGrow.Coms Breeding FAQ
What is combining ability?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 3099 times
Certain inbred lines will display hybrid vigour when crossed. These vigorous lines are said to have favorable combining ability.
Certain inbreds have the ability to combine well with testers--these have general combining ability (GCA). When the inbred combines well only in certain crosses, it has specific combining ability (SCA). The only way to select for combining ability is to grow and examine the progeny. An astute breeder can recognize the potentital for hybrid vigour by identifying the dominant traits of the parents and deducing which lines may combine favorably.
Predicting the combining ability of recessive traits can only be determined through progeny testing.
The breeder is interested in single crosses (also known as F1 generations) that outperform other single crosses. If the breeder has multiple IBLs to work with, she could select first for GCA, then for SCA among the lines with GCA, then identify the best parental gene donors. In most cases with Cannabis you can go directly to selecting for specific combining ability between your IBL and your testers.
What is hybrid vigour?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 2201 times
When two inbred lines from diferent origins are crossed and the resultant progeny produce a better yield or quality due to a better balance of genes, that is hybrid vigour (heterosis). Not all crosses are an improvement on the parents. Random crosses among random lines will give you random results. Hybrid vigour results when the parents used express favorable specific combining ability.
Home : Breeding : Strategies
What are the different types of crosses?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 4645 times
A "single cross" is another name for an F1 hybrid. When two IBLs are crossed the F1 hybrid, or single cross, is the result. This type of cross has the most uniformity and hybrid vigor which makes it the best choice for the home gardener.
A "double cross" is made by crossing two single crosses which come from four separate IBLs. A double cross will be somewhat more variable than a single cross, but will have a wider range of adaptability. This adaptability makes the double cross good for diverse indoor environments.
The "top cross" and the "three way cross" are used as testers. A top cross is an IBL crossed with a variety, and it is used to test for general combining ability.(Ed.note:Only GCA can be found in a topcross.SCA is not sought because one half of the topcross is from a single genotype and the other half is from mixed gametes,therefore,one gene donor is unspecified.) A three way cross is an IBL crossed with an F1. The result of this cross will be one of the parents of the double-cross, and it is used to test for specific combining ability.
A "backcross" is crossing the progeny back to one of its parents,and on another level, to any plant with the same genotype as a Parent. It is designed to improve the parent by retaining most of its qualities and adding a new one. After a series of backcrosses,some degree of uniformity is realized as a result of increased gene frequencies,fixing of some loci through selection and some incidental homozygosity. However, the offspring can only become completely homozygous if the recurrent parent was completely homozygous,and will remain heterozygous for the loci that were heterozygous in the recurrent parent.
A "self cross" is the result of a female Cannabis plant pollinating herself, whether by artificial induction or natural hermaphrodite tendencies. A female that has produced seed from its own pollen is said to be the S0 generation and the resulting seeds are the S1 progeny.
A "full sib" cross is a straight male-female cross between brothers and sisters.
A "half sib" cross uses sister females and unrelated males.
Uncle Ben's pollination method
Added by: 10k Last edited by: 10k Viewed: 2223 times
Contributed by: Uncle Ben
You have several choices for collecting and using pollen. Males will show as a football-like "ball" on a small, short petiole (stem) at the node sites. Once the pollen pods form, they will elongate via a stem, droop, and the flower bracts will open. After about one week after pollen pods first start to form, or upon complete opening of the male flower bracts, the male anther's will shed pollen which will appear as pale, yellow dust.
Males do not take much light to survive once they reach flowering stage. Leave your male plant(s) in the grow room until the first male pollen bracts just begin to crack, and then move 'em into another room with a typical 12/12 schedule, this can be simulated with light thru a window or a fluorescent light fixture.
You have a choice of placing this plant in a very quiet room with no air movement, set on clean paper, or, you can cut the branches off, making a clean slanted cut with a razor blade, and place the branches in a vase of water over paper. Collect the pollen once it begins shedding by placing a glazed ceramic plate or paper plate under the flowers and gently tap the individual branches. Pick out any flowers which tend to drop once in a while.
The pollen will be like dust, so don't visit the garden until you have taken a bath, or you may end up pollinating plants you didn't intend on pollinating.
Collect the pollen over time and place it into a clean vial like a film canister. I really like using a paper plate held under a group of flowers, and then gently thumping the stem. After collecting the pollen, the paper plate can be creased, held over a vial, and the sides and edges thumped until all the pollen is shaken into the vial. Shape the paper plate like a creased funnel.
For a pollen carrier, heat about 2 or 3 teaspoons of flour in an oven set to 180f for 20 minutes or in a small pot set on low heat, let it cool thoroughly, and mix with the pollen to dilute it. I use a ratio of about 1/4 teaspoon pollen to 3 teaspoon flour and have very successful pollination rates. Store in small containers like contact lens cases or film canister, excluding as much air as possible and store in the refrigerator for long term use. Remember, it only takes one male to fertilize one female ovule, and there are millions of pollen cells in a 1/4 teaspoon of pollen so be sure and dilute it.
Use a small artist brush (my preferred method) or toothpick to pollinate a few of the lower branches which have fresh, white pistils, label the pollinated branches, and harvest your seeds in 3 to 6 weeks. I just cure the seeded branches with the rest of the crop, and tear apart the seeded buds with my fingers. You'll find the seeds close to the stem. Store the seeds in the fridge or freezer, labeled of course, with a little dessicant like silica gel or heat treated (sterilized) rice for long term storage.
Kryptonite's pollination method
Added by: Last edited by: 10k Viewed: 3194 times
Contributed by: Kryptonite
Collecting Pollen:
When the first male flowers start to show a possibility of opening, the plant is removed and isolated from the rest of the garden. The male can be placed in a makeshift box, closet, or in an adjacent room.
It is very important to make sure it is secluded from the female garden and there is absolutely NO possibility of pollen drifting into unwanted areas.
It is preferable to have sufficient lighting such as a compact flouroescent fixture, or if "Direct" sunlight from a window source is available that may also be adequate.
The male plant MUST Remain on a 12/12 schedule.
Through Experimentation I have found that if the male does not have ample lighting it will in most cases cease to finish the flowering cycle followed by complete shutdown of pollen production within several days.
Pollen is Easily collected by placing a shot glass or similar item under the flower of which you would like to harvest the pollen from.
Giving a gentle tap to the "ripe" flower with an object such as a pair of tweezers will often cause it to spring open like a parachute and occasionally fall into the glass, "remove them as they fall". It is very important not to let anything that will cause moisture to build in the glass which will result in your pollen caking up on you. Pull the flower from the glass with your tweezers and give it a good tap on the rim of the glass to remove remaining pollen stuck to the flower.
While harvesting Tap the Flowers gently as not to disturb other male flowers on the plant. An agressive Tap will cause pollen to fall from other finished flowers on the plant resulting in a loss of viable pollen.
Male flowers open over a period of several days, during this time you should gather what you deem to be enough for your project, working around the plant as the flowers are ready. A little goes a long way.
It is also helpful if you remove flowers that you have already collected pollen from after each harvest. This is done so that each time you visit your male you can easily Identify Newly ripened flowers.
It is common to catch enough for a small project over a period of 5 days or so after the male flowers have begun to open. At this time the male can either be discarded, consumed, or cloned for future use.
"Naturally" the males flower earlier than the females in order to allow for sufficient overlap. By the time you have finished collecting your pollen the girls should be just about ready to be pollenated.
I would then seclude your best Female for the traits that you want to hopefully preserve from the rest of the garden.
Pollinate early to insure sufficient time for the seed to ripen, most Indica Strains should be pollinated from 10 to 17 days of 12/12 allowing at least 4 weeks for them to finish. It would be preferable to let them finish with the buds, the longer you let your seed ripen the more viable they will be.
Applying the collected Pollen:
If you are not breeding for seed only pollinating the main cola should be avoided, as an example I have personally had excellent results introducing pollen to the secondary colas producing plenty of seed for future use and enough to give to friends.
Now take a cotton swab and gently dab it into the pollen collecting a small amount on the head of the swab, then hovering over the selected buds "female Flowers" that you wish to pollinate give the q-tip a gentle tap with your forefinger and you will see a golden cloud of pollen drift into the bud, try to avoid touching the "hairs" during flowering, It does harm them making them die and wither off.
You can control the fall of the pollen by blowing gently in the direction you want it to travel.
Before placing the girl back into the room make sure you dust it off by blowing excess pollen off of her manually, or you using a hair drying on it's cool setting also works, this will help to insure that you will not have the surplus pollen drifting into unwanted places.
Another good suggestion would be to let the plant sit "secluded" for several hours after pollination, at this time spray a mist of plain PH corrected water over the entire plant "thoroughly".
Wetting of the plant will dampen any residual pollen rendering it non-viable and basically useless. Let the plant sit and dry while it is away from the rest of the garden.
Within 24 to 36 hours you should begin to see the pollinated "hairs" turn reddish or amber, this will show you exactly where to find your seed later.
It is also a good identifier for finding buds pollinated by any occasional excess pollen.
Don't rush their finish, let them go!
I'd hate to see you waste a lot of good bud on immature "green" seeds by not letting them finish fully.
Another tip: In regards to pollinating the lower branches, make sure that you are getting enough light penetration to the area that you have pollinated, if the buds in the areas which lack ample lighting do not usually finish properly neither will your seed.
I'd try to always let them go at least 4.5 to 5 weeks.
The seed is then dried, cured and stored IN the buds, packed neatly in canning jars or bagged in the fridge, taken out as they are needed for use.
This should be a simple easy to use base for you to get started, but please continue Learning through experimantation. By doing this you will find unique ways of customizing this technique that better suits your needs.
Good Luck in your Breeding Endeavors, I hope I have helped you OVERGROW The World!!!!
Soul's Selecting breeding individuals for marijuana production
Added by: Bongaloid Last edited by: ~shabang~ Viewed: 3297 times
Contributed by MrSoul:
Breeding fine cannabis involves carefully choosing the breeding stock. To choose wisely we must first define male and female cannabis:
Female Cannabis
Contributed by British Columbia Grower's Association:
In this first situation, we'll deal with the situation where a plant breeder finds a special individual or clone.
It's a natural thing to be curious and cross a couple of plants that catch your fancy. Grow them out and find a new variation that you like even better. We can preserve the new variation through cloning indefinately, but accidents happen and clones die. They can get viruses or can suffer clonal deprivation from somatic mutations over time. Plus it's harder to share clones with friends through the mail than seeds. So it's only natural that we would want to create seed backups of this special clone.
But before we start breeding this clone, we should try and figure what exactly it is we want from the seeds we are going to create. Do we want them to simply be able to reproduce individuals like the special clone? Simple backcrossing (cubing) will accomplish this. Or do we want to to create seeds that will be able to create more seeds like the special clone, a true breeding strain? These are very different in nature. You see, chances are that your special clone will be heterozygous for many of traits she phenotypically expresses. This just means that she will contain genetic information (genes) for two opposing triats, but you can only see one, the dominant one. However, her seeds will only get one or the other of the genes, so her offspring will express all the genetic information she has, including what you can't see within herself. If you want to create a true breeding strain, you need to preserve all the genes you can see, and remove all the genes that you cannot, but may show up in the offspring. Creating homozygosity. The only way to accomplish this is through selection and generational inbreeding (selecting the homozygous offspring to be parents for the next generation).
BackCrossing and Cubing
Backcrossing is where you breed an individual (your special clone) with it's progeny. Sick in our world, but plants seem to like it
1) Your first backcross is just a backcross.
2) Your second backcross where you take the progeny from the first backcross and cross back to the SAME parent (grandparent now) is often called SQUARING by plant breeders.
3) Your third backcross where you take the progency (squared) from the second backcross and cross back to the SAME parent (great grandparent now) is often called CUBING by plant breeders. You can continue the backcrossing but we just call this backcrossing. Cubing is in reference to the number three, as in 3 backcrosses
Cubing works on the basis of mathamatical probabilities with respect to gene frequencies. The more males you use with each cross, the better the chance that your reality matches the theory. In theory, with the first backcross, 75% of your genepool will match the genepool of the P1 parent being cubed. Squaring increases this to 87.5% and cubing increases it to 93.75%. You can arrive at these numbers by taking the average between the two parents making up the cross. For instance, you start by crossing the P1 mom (100%) with and unrelated male (0%) getting 100% + 0% divided by 2 = 50%. Therefore, the offspring of this first cross are loosly thought of as being 50% like the mom. Take these and do your first backcross and you get 100% (mom) + 50% divided by 2 = 75%. And this is where we get the 75% for the first backcross. Same thing applies as you do more backcrosses. As you will see later, you can apply this same probability math to specific genes or traits, and this can have a dramatic effect on your methodology and selection methods.
Your selection of the right males for each backcross are the crucial points for success with this technique. In each case, you could select males that contain the genes you want, or you could inadvertedly pick those individuals that carry the unwanted recessive genes. Or more likely, you could just pick individuals that are heterozygous for both genes like the P1 mom being backcrossed. The easiest way to deal with this is to start by only looking at one gene and one trait, like lets assume that flavour is determined by a single gene (in reality it's probably not). And do some punnet squares to show gene frequencies through 3 generations of backcrossing. Now lets assume that we found a special pineapple flavoured individual in our pine flavoured population that we wanted to keep. The gene causing the pineapple flavour could be dominant or recessive and the selection abilities and cubing outcome will be different in both cases.
a) pineapple flavour is dominant.
P = pineapple flavour and p = pine flavour
Therefore since each individual will have two flavour genes paired up, the possible genotypes are PP, Pp, and pp. Since P is dominant, PP and Pp will express pineapple flavour while pp will exhibit pine flavour, these are their phenotypes. Now since the pineapple is a new flavour, chances are that the special individual will be heterozygous, or more specifically, Pp. Therefore, the only possible parent combination is Pp X pp with the Pp being the parent to be cubed.
Figure 1. The F1 cross
Now most will find it tough to pick males with the gene for pineapple flavour since males don't produce female flowers. Therefore, they will select males randomly and blindly with respect to this trait. The ratio of P to p genes of the male F1 generation to be used in the first backcross will be 2:6. Another way to look at it is to say that the P gene fequency is 25%. This means that one out of four pollen grains will contain the gene for pineapple flavour. Here is how this plays out in the first backcross.
Figure 2. The B1 cross
Now it's this first backcross that first creates an individual that is homozygous (PP) for the pineapple flavour. However, again because of our limited selection abilities, we choose males randomly. From the random males we should expect three out of eight pollen grains to to contain the gene for pineapple flavour. The P1 female will still contribute one P gene for every p gene. I'll spare your computor's memory and and not post the table, feel free to do it yorself though on paper to be sure you understand what happening
The second backcross (Squaring) will produce the following:
3 PP 8 Pp 5 pp
Therefore, 68.75% will have pineapple flavour and 31.25% will have pine flavour. The frequency of the P gene has risen to 7/16 or 43.75%.
And finally, the third backcross (Cubing) will net the following genotypic ratios:
7PP 16Pp 9pp
Therefore, 71.875% will have pineapple flavour after cubing has been completed. Roughly 22% (7/32*100) of the cubed progeny will be true breeding for the pineapple flavour. The frequency of the P gene has risen to roughly 47% (30/64).
In conclusion, if the backcrossing continued indefinately with random selection of males and with large enough of a population size, the frequency of the P gene would max out at 50%. This means that the best that can be expected from cubing is 25% true breeding for pineapple flavour and 75% that will display the pineapple flavour. You would never be rid of the 25% that would maintain the pine flavour. This model would hold true when trying to cube any heterozygous trait.
b) Pineapple flavour is recessive
In this case, P is for the pine flavour and p is for pineapple flavour. Convention is that the capital letter signifies dominance. For the breeder to have noticed the interesting trait, the mom to be cubed would have to be homozygous for the pineapple flavour (pp). Depending where the male came from and whether it was related, it could be Pp or PP, with PP being more likely. It won't make much difference which in the outcome.
F1 cross is pretty basic, we'll skip the diagram. We simply cross the female (pp) with the male (PP) and get offspring that are all Pp. Since the pine flavour is recessive, none of the F1 offspring will have pineapple flavour (hint ). However, the frequency of the gene p will be 50%.
pp X PP = Pp + Pp + Pp + Pp
Since the F1 generation are all the same (Pp), the pollen it donates to the first backcross will contain a p gene for every P gene. The first backcross will be:
B1 = pp X Pp = Pp + Pp + pp + pp
As you can see, 50% of the offspring will be pineapple flavoured and the frequency of the p gene is 6/8 or 75%. This B1 generation will generate pollen containing 6 p genes for every 2 P genes.
Figure 3. The second backcross.
As you can see, the second backcross or squaring produces pineapple flavour in 75% of the offspring. And the p gene frequency within those offspring is roughly 88%. (Remember C88 ). Of the pollen grains from this squaring, 14 out of 16 will carry the p gene for pineapple flavouring. When they are backcrossed to the P1 mom for the third time, they net the following cubed progeny:
Figure 4. The third backcross
After cubing of a homozygous gene pair, we end up with roughly 88% of them displaying the desired trait (pineapple flavour in this case) and also being true breeding for that same trait. The frequency of this desired gene will be roughly 94%. If the backcrossing was to continue indefinately, the gene frequency would continue to approach 100% but never entirely get there.
It should be noted that the above examples assume no selective pressure and large enough population sizes to ensure random matings. As the number of males used in each generation decreases, the greater the selective pressure whether intended or not. The significance of a breeding population size and selective pressure is much greater when the traits to be cubed are heterozygous. And most importantly, the above examples only take into account for a single gene pair.
In reality, most of the traits we select for like potency are influenced by several traits. Then the math gets more complicated if you want to figure out the success rate of a cubing project. Generally speaking, you multiply the probabilities of achieving each trait against each other. For example, if your pineapple trait was influenced by 2 seperate recessive genes, then you would multiply 87.5% * 87.5% (.875 * .875 *100) and get 76.6%. This means that 76.6% of the offspring would be pineapple flavoured. Now lets say the pineapple trait is influenced by 2 recessive traits and and a heterozygous dominant one. We would multiply 87.5% by 87.5% by 71.9% (.875*.875*.719*100) and get 55%. Just by increasing to three genes, we have decreased the number of cubed offspring having pineapple flavouring down to 55%. Therefore, cubing is a good technique where you want to increase the frequency of a few genes (this is an important point to remember ), but as the project increases, the chance of success decreases .... at least without some level of selective pressure.
Applying the pressure
The best way to significantly increase your chances of success is to apply intended selective pressure and eliminate unintentional selective pressure. Try to find clearcut and efficient ways to isolate and select for and against certain traits. Find ways to be sure your males are passing along the intended traits and remove all males that do not. This includes ALL traits that may be selected for. Some traits you will be able to observe directly in the males. Other traits like flowering duration you may not. If you are selecting for a trait you can't directly observe, you want to do some progeny tests and determine which males pass on the most desireable genes. I'll explain more on progeny tests later.
It's important that when chosing your best males to ignore the superficial traits having nothing to do with the real traits your looking for. You see, cannabis has several thousand genes residing on just 10 chromosome pairs or 20 individual chromosomes. Therefore each chomosome contains hundred of genes. Each gene residing on the same chromosome is said to be linked to each other. Generally speaking, they travel as a group . If you select for one of them, you are actually selecting for all of the traits on the chromosome. There is an exception to this rule refferred to as breaking linked genes via crossing over, but for simplicity sake, we will ignore that for now. Getting back to selection, you could decide to select for a trait such as you like the spikey look of the leaves while really being interested in fixing the grapefruit flavour. But as it may happen, both traits may be on the same chromosome pair but opposite chromosomes. If so, as long as you select the plants with spikey leaves, you will never get the grapefruit flavour you really want. It's good to keep in mind that each time you select for a triat, you are selecting against several hundred genes This is why most serious breeders learn to take small methodical steps and work on one or two traits at a time. Especially with inbreeding projects such as selfing and backcrossing.
Now lets see what kind of improvements we can make in the first example of trying to cube a heterozygous dominant trait using some selective pressure. Lets say that with each generation, we are able to remove the individuals recessive for the pine flavour (pp), but can't remove the heterozygous ones (Pp). If you recall, our P1 mom had the genotype (Pp) in that model and the F1 cross yielded (Pp + Pp + pp + pp) as possible offspring combinations. We remove the two (pp) individuals leaving us with only Pp. Therefore our first backcross will be:
Pp * Pp = PP + Pp + Pp + pp
Again we remove the pp individual leaving us with PP + 2Pp. Going into the second backcross we have increased our P gene frequency from 37.5% up to 66.7%. This means that going into the second backcross 4 of every six pollen grains will carry the P gene. The outcome is as follows
As you can see, after selecting against the homozygous recessives for 2 backcrosses, we have increased our P gene frequency to 58% from 44% in our squared population. If we again remove the homozygous recessives, our gene frequency increases to 70% (14/20) going into the third backcross, meaning that 7 out of 10 pollen grains will carry the P gene. Again, I'll spare your PC's memory and just give your the results of the third backcross.
B3 cross = 7 PP + 10 Pp + 3 pp
This translates to mean that 95% of the progeny will taste like pineapple after cubing a heterozygous dominant strain if the homozygous pine tasting ones are removed prior to to each backcross. This is an improvent from 72% when no selection occurred. The frequency of individuals true breeding for the pineapple flavour rose to 35%. But more importantly, the P gene frequency improves to 60%. This will be an important consideration when we discuss progeny testing .
But for now lets recap the percentage of individuals true breeding for the pineapple taste in each of the models. In the case where the pineapple flavour trait is heterozygous dominant and no selective pressure is used, cubing produced 22% true breeding individuals. By selecting against the homozygous pine recessive, we were able to increase this too 35%. And finally, when cubing a homozygous recessive gene, we are able to achieve a cubed population that is 87.5% true breeding for the pineapple flavour. And as I pointed out earlier, these numbers only apply to single gene traits. Lets say the pineapple flavour is coded by two seperate genes, one dominant and one recessive, and you are able to select against the homozygous recessive pine flavour while selecting for the dominant pineapple flavour gene. Your cubed population would then contain 87.5% * 35% (.875 * .35 * 100) = 30% true breeding individuals. As you can see, as long as the cubed source is heterozygous, it doesn't matter how many backcrosses you do, you will never achieve a true breeding strain.
What is cubing?
Added by: Team GrowFAQ Viewed: 1457 times
Contributed by MrSoul:
An alternative F1 hybrid breeding method I
Contributed by Vic High:
What really is an F1 cross?
Well defining the terms P1, F1, F2, homozygous, and heterogygous can be a simple task, however, applying them to applied genetics can often create confusion. Depending on your point of reference, a plant could be described as any of these terms. For our specific field of interest it's important to further define these terms to reduce confusion and protect the consumers. First I'll provide the classic scientific definition of these and other related terms and then I'll dive into each term into detail.
Heterzygous - a condition when two genes for a trait are not the same on each member of a pair of homologous chromosomes; individuals heterozygous for a trait are indicated by an "Aa" or "aA" notation and are not true breeding for that trait.(Clarke)
Homozygous - the condition existing when the genes for a trait are the same on both chromosomes of a homologous pair; individuals homozygous for a trait are indicated by "AA" or "aa" and are true breeding for that trait. (Clarke)
- Now the heterozygous and homozygous terms can be applied to one trait or a group of traits within an individual or a group of individuals. Depending on your point of reference, an individual or group can be
considered both homozygous or heterozygous. For instance, say you have two individuals that are both short (S) and have webbed leaves (W) and have the following genotypes.
#1 = SSWW
#2 = SSWw
They are both homozygous for the short trait but only individual #1 is homozygous for the webbed leaf trait. Individual #2 is heterozygous for the webbed leaf trait and would be considered a heterozygous individual. As a goup, they would be considered heterozygous in general by some and homozygous by others. It would depend on your point of reference and the overall importance you place on the webbed leaf trait. Most would consider it to be heterozygous.
For example, the blueberry cannabis strain is considered a true breeding homozygous seed line because as a whole the many offspring have a similar look and produce a similar product. However there are often subtle differences between the plants of characters such as stem colour and potency. When taking a close look at blueberry, you will find heterozygous traits, but because of the whole overall look, we still generally consider them homozygous for the purpose of breeding programs. Using dogs is another way to explain this, take a dobie for example, you cant tell the difference between dobies, but you can tell a dobie from another breed. Ya follow?
Hybrid - An individual produced by crossing two parents of different genotypes. Clarke says that a hybrid is a heterozygous individual resulting from crossing two seperate strains.
- For the purpose of seedbanks, a hybrid is in general, a cross between any two unrelated seedlines. ANY HYBRID IS heterozygous and NOT TRUE BREEDING.
F1 hybrid - is the first generation of a cross between any two unrelated seedlines in the creation of a hybrid. F1 hybrids can be uniform or variable depending on the P1 parent stock used.
F2 hybrid - is the offspring of a cross between two F1 plants (Clarke). What Clarke and other sources don't make clear is do the two F1's need to be from the same parents? By convention they don't. As well, german geneticists often describe a backcross of an F1 back to a P1 parent as a F2 cross.
- OK lets say we take blueberry and cross it with romulan (both relatively true breeding of their unique traits) to create the F1 hybrid romberry. Now lets cross the F1 romberry with a NL/Haze F1 hybrid. (Ed.note:The textbooks consider this a 'double cross'.)
Some could say this is a F1 cross of romberry and NL/Haze. Others could argue that it is a F2 cross of two F1 hybrids. Gets confusing doesn't it? Now lets cross this Romberry/NL/Haze(RNH) with a Skunk#1/NL#5 F1 hybrid to create RNHSN. Now some would argue that RNHSN is an F1 hybrid between RNH and SK/NL seedlines. Others would call it an F2.
- So what does this mean to the consumer? It means that a seed bank can call a cross whatever it wants until the industry adopts some standards. This is what this article will attempt to initiate. Clarke eludes to
standardising these definitions but never really gets around to it. Fortunately other plant breeding communities have (Colangelli, Grossnickle&Russell, Watts, &Wright) and adopting their standards
makes the most sense and offers the best protection to the seedbank consumer.
Watts defines an F1 as the heterozygous offspring between two homozygous but unrelated seedlines. This makes sense and gives the F1 generation a unique combination of traits; uniform phenotype but not true breeding. This is important in the plant breeding world. This means that when a customer buys F1 seeds that they should expect uniform results. It also means that the breeder's work is protected from being duplicated by any other means than using the original P1 (true breeding parents). [There are
exceptions to this by using techniques such as repeated backcrosses (cubing the clone).
F2 crosses are the offspring of crossing two F1 hybrids. This means that they will not be uniform nor will they breed true. However, F3, F4, F5, etc will also share these characteristics, so to simplify terminology for the seedbanks and seedbank merchants, they can all be classified as F2 seeds in general.
What does this mean for the preceeding example? Well, the blueberry, romulan, skunk#1, NL#5, and haze were all P1 true breeding seedlines or strains (another term that needs clarification). Romberry, NL/Haze, and SK/NL were all F1 hybrids. Both the Romberry/NL/Haze and the RNHSN would be F2s. Within each group the consumer can know what to expect for the price they are paying.
Few cannabis seedbanks (if any) and their breeders are following these definitions and are subsequently creating confusion within the cannabis seedbuying community. This is a change that needs to happen.
Note: this is a rough draft to be published to the internet. Hopefully in time it or something similar will be used to help establish an industry standard. Any comments and critism is welcome to aid in the production of the final draft. Small steps like this can only benefit the cannabis community over the long haul.
REFERENCES:
Clarke RC. 1981. Marijuana Botony Ronin Publishing, California
Colangeli AM. 1989. Advanced Biology notes. University of Victoria, BC
Futuyma DJ. 1986. Evolutionary Biology Sinauer Associates, Inc. Massachusetts
Klug & Cummings. 1986. Concepts of Genetics 2nd ed. Scott, Foresman, & comp. Illinois
Grossnickle & Russell. 1989. Stock quality improvement of yellow-cedar. Canada-BC Forest Resources Developement Agreement (F.R.D.A.) Project 2.40
Watts. 1980. Flower & Vegetable Plant Breeding Grower Books, London
Wright JW Introduction to Forest Genetics Academic Press, San Francisco
What is linkage?
Added by: MR_NATURAL420 Last edited by: MR_NATURAL420 Viewed: 989 times
Genes located on the same chromosome are not randomly assorted but tend to be inherited together. This is known as linkage. Plants depend on a large number of factors for their phenotype and linked factors are usually dominant. Linkage adds to the difficulty of combining favorable factors of parents of a cross. Large populations are needed to obtain recombination and find that rare but desirable individual.
(Did you notice UncleBens Pollination method in there?)
)I found an old disk from before I ripped out my old hard drive and left the country for a year. There is a bunch of usefull info in there, but yes it is VERY long. But hey what do you want from old Brothers Grim and Vic High info, good score I think. Peace
OverGrow.Coms Breeding FAQ
What is combining ability?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 3099 times
Certain inbred lines will display hybrid vigour when crossed. These vigorous lines are said to have favorable combining ability.
Certain inbreds have the ability to combine well with testers--these have general combining ability (GCA). When the inbred combines well only in certain crosses, it has specific combining ability (SCA). The only way to select for combining ability is to grow and examine the progeny. An astute breeder can recognize the potentital for hybrid vigour by identifying the dominant traits of the parents and deducing which lines may combine favorably.
Predicting the combining ability of recessive traits can only be determined through progeny testing.
The breeder is interested in single crosses (also known as F1 generations) that outperform other single crosses. If the breeder has multiple IBLs to work with, she could select first for GCA, then for SCA among the lines with GCA, then identify the best parental gene donors. In most cases with Cannabis you can go directly to selecting for specific combining ability between your IBL and your testers.
What is hybrid vigour?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 2201 times
When two inbred lines from diferent origins are crossed and the resultant progeny produce a better yield or quality due to a better balance of genes, that is hybrid vigour (heterosis). Not all crosses are an improvement on the parents. Random crosses among random lines will give you random results. Hybrid vigour results when the parents used express favorable specific combining ability.
Home : Breeding : Strategies
What are the different types of crosses?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 4645 times
A "single cross" is another name for an F1 hybrid. When two IBLs are crossed the F1 hybrid, or single cross, is the result. This type of cross has the most uniformity and hybrid vigor which makes it the best choice for the home gardener.
A "double cross" is made by crossing two single crosses which come from four separate IBLs. A double cross will be somewhat more variable than a single cross, but will have a wider range of adaptability. This adaptability makes the double cross good for diverse indoor environments.
The "top cross" and the "three way cross" are used as testers. A top cross is an IBL crossed with a variety, and it is used to test for general combining ability.(Ed.note:Only GCA can be found in a topcross.SCA is not sought because one half of the topcross is from a single genotype and the other half is from mixed gametes,therefore,one gene donor is unspecified.) A three way cross is an IBL crossed with an F1. The result of this cross will be one of the parents of the double-cross, and it is used to test for specific combining ability.
A "backcross" is crossing the progeny back to one of its parents,and on another level, to any plant with the same genotype as a Parent. It is designed to improve the parent by retaining most of its qualities and adding a new one. After a series of backcrosses,some degree of uniformity is realized as a result of increased gene frequencies,fixing of some loci through selection and some incidental homozygosity. However, the offspring can only become completely homozygous if the recurrent parent was completely homozygous,and will remain heterozygous for the loci that were heterozygous in the recurrent parent.
A "self cross" is the result of a female Cannabis plant pollinating herself, whether by artificial induction or natural hermaphrodite tendencies. A female that has produced seed from its own pollen is said to be the S0 generation and the resulting seeds are the S1 progeny.
A "full sib" cross is a straight male-female cross between brothers and sisters.
A "half sib" cross uses sister females and unrelated males.
Uncle Ben's pollination method
Added by: 10k Last edited by: 10k Viewed: 2223 times
Contributed by: Uncle Ben
You have several choices for collecting and using pollen. Males will show as a football-like "ball" on a small, short petiole (stem) at the node sites. Once the pollen pods form, they will elongate via a stem, droop, and the flower bracts will open. After about one week after pollen pods first start to form, or upon complete opening of the male flower bracts, the male anther's will shed pollen which will appear as pale, yellow dust.
Males do not take much light to survive once they reach flowering stage. Leave your male plant(s) in the grow room until the first male pollen bracts just begin to crack, and then move 'em into another room with a typical 12/12 schedule, this can be simulated with light thru a window or a fluorescent light fixture.
You have a choice of placing this plant in a very quiet room with no air movement, set on clean paper, or, you can cut the branches off, making a clean slanted cut with a razor blade, and place the branches in a vase of water over paper. Collect the pollen once it begins shedding by placing a glazed ceramic plate or paper plate under the flowers and gently tap the individual branches. Pick out any flowers which tend to drop once in a while.
The pollen will be like dust, so don't visit the garden until you have taken a bath, or you may end up pollinating plants you didn't intend on pollinating.
Collect the pollen over time and place it into a clean vial like a film canister. I really like using a paper plate held under a group of flowers, and then gently thumping the stem. After collecting the pollen, the paper plate can be creased, held over a vial, and the sides and edges thumped until all the pollen is shaken into the vial. Shape the paper plate like a creased funnel.
For a pollen carrier, heat about 2 or 3 teaspoons of flour in an oven set to 180f for 20 minutes or in a small pot set on low heat, let it cool thoroughly, and mix with the pollen to dilute it. I use a ratio of about 1/4 teaspoon pollen to 3 teaspoon flour and have very successful pollination rates. Store in small containers like contact lens cases or film canister, excluding as much air as possible and store in the refrigerator for long term use. Remember, it only takes one male to fertilize one female ovule, and there are millions of pollen cells in a 1/4 teaspoon of pollen so be sure and dilute it.
Use a small artist brush (my preferred method) or toothpick to pollinate a few of the lower branches which have fresh, white pistils, label the pollinated branches, and harvest your seeds in 3 to 6 weeks. I just cure the seeded branches with the rest of the crop, and tear apart the seeded buds with my fingers. You'll find the seeds close to the stem. Store the seeds in the fridge or freezer, labeled of course, with a little dessicant like silica gel or heat treated (sterilized) rice for long term storage.
Kryptonite's pollination method
Added by: Last edited by: 10k Viewed: 3194 times
Contributed by: Kryptonite
Collecting Pollen:
When the first male flowers start to show a possibility of opening, the plant is removed and isolated from the rest of the garden. The male can be placed in a makeshift box, closet, or in an adjacent room.
It is very important to make sure it is secluded from the female garden and there is absolutely NO possibility of pollen drifting into unwanted areas.
It is preferable to have sufficient lighting such as a compact flouroescent fixture, or if "Direct" sunlight from a window source is available that may also be adequate.
The male plant MUST Remain on a 12/12 schedule.
Through Experimentation I have found that if the male does not have ample lighting it will in most cases cease to finish the flowering cycle followed by complete shutdown of pollen production within several days.
Pollen is Easily collected by placing a shot glass or similar item under the flower of which you would like to harvest the pollen from.
Giving a gentle tap to the "ripe" flower with an object such as a pair of tweezers will often cause it to spring open like a parachute and occasionally fall into the glass, "remove them as they fall". It is very important not to let anything that will cause moisture to build in the glass which will result in your pollen caking up on you. Pull the flower from the glass with your tweezers and give it a good tap on the rim of the glass to remove remaining pollen stuck to the flower.
While harvesting Tap the Flowers gently as not to disturb other male flowers on the plant. An agressive Tap will cause pollen to fall from other finished flowers on the plant resulting in a loss of viable pollen.
Male flowers open over a period of several days, during this time you should gather what you deem to be enough for your project, working around the plant as the flowers are ready. A little goes a long way.
It is also helpful if you remove flowers that you have already collected pollen from after each harvest. This is done so that each time you visit your male you can easily Identify Newly ripened flowers.
It is common to catch enough for a small project over a period of 5 days or so after the male flowers have begun to open. At this time the male can either be discarded, consumed, or cloned for future use.
"Naturally" the males flower earlier than the females in order to allow for sufficient overlap. By the time you have finished collecting your pollen the girls should be just about ready to be pollenated.
I would then seclude your best Female for the traits that you want to hopefully preserve from the rest of the garden.
Pollinate early to insure sufficient time for the seed to ripen, most Indica Strains should be pollinated from 10 to 17 days of 12/12 allowing at least 4 weeks for them to finish. It would be preferable to let them finish with the buds, the longer you let your seed ripen the more viable they will be.
Applying the collected Pollen:
If you are not breeding for seed only pollinating the main cola should be avoided, as an example I have personally had excellent results introducing pollen to the secondary colas producing plenty of seed for future use and enough to give to friends.
Now take a cotton swab and gently dab it into the pollen collecting a small amount on the head of the swab, then hovering over the selected buds "female Flowers" that you wish to pollinate give the q-tip a gentle tap with your forefinger and you will see a golden cloud of pollen drift into the bud, try to avoid touching the "hairs" during flowering, It does harm them making them die and wither off.
You can control the fall of the pollen by blowing gently in the direction you want it to travel.
Before placing the girl back into the room make sure you dust it off by blowing excess pollen off of her manually, or you using a hair drying on it's cool setting also works, this will help to insure that you will not have the surplus pollen drifting into unwanted places.
Another good suggestion would be to let the plant sit "secluded" for several hours after pollination, at this time spray a mist of plain PH corrected water over the entire plant "thoroughly".
Wetting of the plant will dampen any residual pollen rendering it non-viable and basically useless. Let the plant sit and dry while it is away from the rest of the garden.
Within 24 to 36 hours you should begin to see the pollinated "hairs" turn reddish or amber, this will show you exactly where to find your seed later.
It is also a good identifier for finding buds pollinated by any occasional excess pollen.
Don't rush their finish, let them go!
I'd hate to see you waste a lot of good bud on immature "green" seeds by not letting them finish fully.
Another tip: In regards to pollinating the lower branches, make sure that you are getting enough light penetration to the area that you have pollinated, if the buds in the areas which lack ample lighting do not usually finish properly neither will your seed.
I'd try to always let them go at least 4.5 to 5 weeks.
The seed is then dried, cured and stored IN the buds, packed neatly in canning jars or bagged in the fridge, taken out as they are needed for use.
This should be a simple easy to use base for you to get started, but please continue Learning through experimantation. By doing this you will find unique ways of customizing this technique that better suits your needs.
Good Luck in your Breeding Endeavors, I hope I have helped you OVERGROW The World!!!!
Soul's Selecting breeding individuals for marijuana production
Added by: Bongaloid Last edited by: ~shabang~ Viewed: 3297 times
Contributed by MrSoul:
Breeding fine cannabis involves carefully choosing the breeding stock. To choose wisely we must first define male and female cannabis:
Female Cannabis
Contributed by British Columbia Grower's Association:
In this first situation, we'll deal with the situation where a plant breeder finds a special individual or clone.
It's a natural thing to be curious and cross a couple of plants that catch your fancy. Grow them out and find a new variation that you like even better. We can preserve the new variation through cloning indefinately, but accidents happen and clones die. They can get viruses or can suffer clonal deprivation from somatic mutations over time. Plus it's harder to share clones with friends through the mail than seeds. So it's only natural that we would want to create seed backups of this special clone.
But before we start breeding this clone, we should try and figure what exactly it is we want from the seeds we are going to create. Do we want them to simply be able to reproduce individuals like the special clone? Simple backcrossing (cubing) will accomplish this. Or do we want to to create seeds that will be able to create more seeds like the special clone, a true breeding strain? These are very different in nature. You see, chances are that your special clone will be heterozygous for many of traits she phenotypically expresses. This just means that she will contain genetic information (genes) for two opposing triats, but you can only see one, the dominant one. However, her seeds will only get one or the other of the genes, so her offspring will express all the genetic information she has, including what you can't see within herself. If you want to create a true breeding strain, you need to preserve all the genes you can see, and remove all the genes that you cannot, but may show up in the offspring. Creating homozygosity. The only way to accomplish this is through selection and generational inbreeding (selecting the homozygous offspring to be parents for the next generation).
BackCrossing and Cubing
Backcrossing is where you breed an individual (your special clone) with it's progeny. Sick in our world, but plants seem to like it
1) Your first backcross is just a backcross.
2) Your second backcross where you take the progeny from the first backcross and cross back to the SAME parent (grandparent now) is often called SQUARING by plant breeders.
3) Your third backcross where you take the progency (squared) from the second backcross and cross back to the SAME parent (great grandparent now) is often called CUBING by plant breeders. You can continue the backcrossing but we just call this backcrossing. Cubing is in reference to the number three, as in 3 backcrosses
Cubing works on the basis of mathamatical probabilities with respect to gene frequencies. The more males you use with each cross, the better the chance that your reality matches the theory. In theory, with the first backcross, 75% of your genepool will match the genepool of the P1 parent being cubed. Squaring increases this to 87.5% and cubing increases it to 93.75%. You can arrive at these numbers by taking the average between the two parents making up the cross. For instance, you start by crossing the P1 mom (100%) with and unrelated male (0%) getting 100% + 0% divided by 2 = 50%. Therefore, the offspring of this first cross are loosly thought of as being 50% like the mom. Take these and do your first backcross and you get 100% (mom) + 50% divided by 2 = 75%. And this is where we get the 75% for the first backcross. Same thing applies as you do more backcrosses. As you will see later, you can apply this same probability math to specific genes or traits, and this can have a dramatic effect on your methodology and selection methods.
Your selection of the right males for each backcross are the crucial points for success with this technique. In each case, you could select males that contain the genes you want, or you could inadvertedly pick those individuals that carry the unwanted recessive genes. Or more likely, you could just pick individuals that are heterozygous for both genes like the P1 mom being backcrossed. The easiest way to deal with this is to start by only looking at one gene and one trait, like lets assume that flavour is determined by a single gene (in reality it's probably not). And do some punnet squares to show gene frequencies through 3 generations of backcrossing. Now lets assume that we found a special pineapple flavoured individual in our pine flavoured population that we wanted to keep. The gene causing the pineapple flavour could be dominant or recessive and the selection abilities and cubing outcome will be different in both cases.
a) pineapple flavour is dominant.
P = pineapple flavour and p = pine flavour
Therefore since each individual will have two flavour genes paired up, the possible genotypes are PP, Pp, and pp. Since P is dominant, PP and Pp will express pineapple flavour while pp will exhibit pine flavour, these are their phenotypes. Now since the pineapple is a new flavour, chances are that the special individual will be heterozygous, or more specifically, Pp. Therefore, the only possible parent combination is Pp X pp with the Pp being the parent to be cubed.
Figure 1. The F1 cross
Now most will find it tough to pick males with the gene for pineapple flavour since males don't produce female flowers. Therefore, they will select males randomly and blindly with respect to this trait. The ratio of P to p genes of the male F1 generation to be used in the first backcross will be 2:6. Another way to look at it is to say that the P gene fequency is 25%. This means that one out of four pollen grains will contain the gene for pineapple flavour. Here is how this plays out in the first backcross.
Figure 2. The B1 cross
Now it's this first backcross that first creates an individual that is homozygous (PP) for the pineapple flavour. However, again because of our limited selection abilities, we choose males randomly. From the random males we should expect three out of eight pollen grains to to contain the gene for pineapple flavour. The P1 female will still contribute one P gene for every p gene. I'll spare your computor's memory and and not post the table, feel free to do it yorself though on paper to be sure you understand what happening
The second backcross (Squaring) will produce the following:
3 PP 8 Pp 5 pp
Therefore, 68.75% will have pineapple flavour and 31.25% will have pine flavour. The frequency of the P gene has risen to 7/16 or 43.75%.
And finally, the third backcross (Cubing) will net the following genotypic ratios:
7PP 16Pp 9pp
Therefore, 71.875% will have pineapple flavour after cubing has been completed. Roughly 22% (7/32*100) of the cubed progeny will be true breeding for the pineapple flavour. The frequency of the P gene has risen to roughly 47% (30/64).
In conclusion, if the backcrossing continued indefinately with random selection of males and with large enough of a population size, the frequency of the P gene would max out at 50%. This means that the best that can be expected from cubing is 25% true breeding for pineapple flavour and 75% that will display the pineapple flavour. You would never be rid of the 25% that would maintain the pine flavour. This model would hold true when trying to cube any heterozygous trait.
b) Pineapple flavour is recessive
In this case, P is for the pine flavour and p is for pineapple flavour. Convention is that the capital letter signifies dominance. For the breeder to have noticed the interesting trait, the mom to be cubed would have to be homozygous for the pineapple flavour (pp). Depending where the male came from and whether it was related, it could be Pp or PP, with PP being more likely. It won't make much difference which in the outcome.
F1 cross is pretty basic, we'll skip the diagram. We simply cross the female (pp) with the male (PP) and get offspring that are all Pp. Since the pine flavour is recessive, none of the F1 offspring will have pineapple flavour (hint ). However, the frequency of the gene p will be 50%.
pp X PP = Pp + Pp + Pp + Pp
Since the F1 generation are all the same (Pp), the pollen it donates to the first backcross will contain a p gene for every P gene. The first backcross will be:
B1 = pp X Pp = Pp + Pp + pp + pp
As you can see, 50% of the offspring will be pineapple flavoured and the frequency of the p gene is 6/8 or 75%. This B1 generation will generate pollen containing 6 p genes for every 2 P genes.
Figure 3. The second backcross.
As you can see, the second backcross or squaring produces pineapple flavour in 75% of the offspring. And the p gene frequency within those offspring is roughly 88%. (Remember C88 ). Of the pollen grains from this squaring, 14 out of 16 will carry the p gene for pineapple flavouring. When they are backcrossed to the P1 mom for the third time, they net the following cubed progeny:
Figure 4. The third backcross
After cubing of a homozygous gene pair, we end up with roughly 88% of them displaying the desired trait (pineapple flavour in this case) and also being true breeding for that same trait. The frequency of this desired gene will be roughly 94%. If the backcrossing was to continue indefinately, the gene frequency would continue to approach 100% but never entirely get there.
It should be noted that the above examples assume no selective pressure and large enough population sizes to ensure random matings. As the number of males used in each generation decreases, the greater the selective pressure whether intended or not. The significance of a breeding population size and selective pressure is much greater when the traits to be cubed are heterozygous. And most importantly, the above examples only take into account for a single gene pair.
In reality, most of the traits we select for like potency are influenced by several traits. Then the math gets more complicated if you want to figure out the success rate of a cubing project. Generally speaking, you multiply the probabilities of achieving each trait against each other. For example, if your pineapple trait was influenced by 2 seperate recessive genes, then you would multiply 87.5% * 87.5% (.875 * .875 *100) and get 76.6%. This means that 76.6% of the offspring would be pineapple flavoured. Now lets say the pineapple trait is influenced by 2 recessive traits and and a heterozygous dominant one. We would multiply 87.5% by 87.5% by 71.9% (.875*.875*.719*100) and get 55%. Just by increasing to three genes, we have decreased the number of cubed offspring having pineapple flavouring down to 55%. Therefore, cubing is a good technique where you want to increase the frequency of a few genes (this is an important point to remember ), but as the project increases, the chance of success decreases .... at least without some level of selective pressure.
Applying the pressure
The best way to significantly increase your chances of success is to apply intended selective pressure and eliminate unintentional selective pressure. Try to find clearcut and efficient ways to isolate and select for and against certain traits. Find ways to be sure your males are passing along the intended traits and remove all males that do not. This includes ALL traits that may be selected for. Some traits you will be able to observe directly in the males. Other traits like flowering duration you may not. If you are selecting for a trait you can't directly observe, you want to do some progeny tests and determine which males pass on the most desireable genes. I'll explain more on progeny tests later.
It's important that when chosing your best males to ignore the superficial traits having nothing to do with the real traits your looking for. You see, cannabis has several thousand genes residing on just 10 chromosome pairs or 20 individual chromosomes. Therefore each chomosome contains hundred of genes. Each gene residing on the same chromosome is said to be linked to each other. Generally speaking, they travel as a group . If you select for one of them, you are actually selecting for all of the traits on the chromosome. There is an exception to this rule refferred to as breaking linked genes via crossing over, but for simplicity sake, we will ignore that for now. Getting back to selection, you could decide to select for a trait such as you like the spikey look of the leaves while really being interested in fixing the grapefruit flavour. But as it may happen, both traits may be on the same chromosome pair but opposite chromosomes. If so, as long as you select the plants with spikey leaves, you will never get the grapefruit flavour you really want. It's good to keep in mind that each time you select for a triat, you are selecting against several hundred genes This is why most serious breeders learn to take small methodical steps and work on one or two traits at a time. Especially with inbreeding projects such as selfing and backcrossing.
Now lets see what kind of improvements we can make in the first example of trying to cube a heterozygous dominant trait using some selective pressure. Lets say that with each generation, we are able to remove the individuals recessive for the pine flavour (pp), but can't remove the heterozygous ones (Pp). If you recall, our P1 mom had the genotype (Pp) in that model and the F1 cross yielded (Pp + Pp + pp + pp) as possible offspring combinations. We remove the two (pp) individuals leaving us with only Pp. Therefore our first backcross will be:
Pp * Pp = PP + Pp + Pp + pp
Again we remove the pp individual leaving us with PP + 2Pp. Going into the second backcross we have increased our P gene frequency from 37.5% up to 66.7%. This means that going into the second backcross 4 of every six pollen grains will carry the P gene. The outcome is as follows
As you can see, after selecting against the homozygous recessives for 2 backcrosses, we have increased our P gene frequency to 58% from 44% in our squared population. If we again remove the homozygous recessives, our gene frequency increases to 70% (14/20) going into the third backcross, meaning that 7 out of 10 pollen grains will carry the P gene. Again, I'll spare your PC's memory and just give your the results of the third backcross.
B3 cross = 7 PP + 10 Pp + 3 pp
This translates to mean that 95% of the progeny will taste like pineapple after cubing a heterozygous dominant strain if the homozygous pine tasting ones are removed prior to to each backcross. This is an improvent from 72% when no selection occurred. The frequency of individuals true breeding for the pineapple flavour rose to 35%. But more importantly, the P gene frequency improves to 60%. This will be an important consideration when we discuss progeny testing .
But for now lets recap the percentage of individuals true breeding for the pineapple taste in each of the models. In the case where the pineapple flavour trait is heterozygous dominant and no selective pressure is used, cubing produced 22% true breeding individuals. By selecting against the homozygous pine recessive, we were able to increase this too 35%. And finally, when cubing a homozygous recessive gene, we are able to achieve a cubed population that is 87.5% true breeding for the pineapple flavour. And as I pointed out earlier, these numbers only apply to single gene traits. Lets say the pineapple flavour is coded by two seperate genes, one dominant and one recessive, and you are able to select against the homozygous recessive pine flavour while selecting for the dominant pineapple flavour gene. Your cubed population would then contain 87.5% * 35% (.875 * .35 * 100) = 30% true breeding individuals. As you can see, as long as the cubed source is heterozygous, it doesn't matter how many backcrosses you do, you will never achieve a true breeding strain.
What is cubing?
Added by: Team GrowFAQ Viewed: 1457 times
Contributed by MrSoul:
An alternative F1 hybrid breeding method I
Contributed by Vic High:
What really is an F1 cross?
Well defining the terms P1, F1, F2, homozygous, and heterogygous can be a simple task, however, applying them to applied genetics can often create confusion. Depending on your point of reference, a plant could be described as any of these terms. For our specific field of interest it's important to further define these terms to reduce confusion and protect the consumers. First I'll provide the classic scientific definition of these and other related terms and then I'll dive into each term into detail.
Heterzygous - a condition when two genes for a trait are not the same on each member of a pair of homologous chromosomes; individuals heterozygous for a trait are indicated by an "Aa" or "aA" notation and are not true breeding for that trait.(Clarke)
Homozygous - the condition existing when the genes for a trait are the same on both chromosomes of a homologous pair; individuals homozygous for a trait are indicated by "AA" or "aa" and are true breeding for that trait. (Clarke)
- Now the heterozygous and homozygous terms can be applied to one trait or a group of traits within an individual or a group of individuals. Depending on your point of reference, an individual or group can be
considered both homozygous or heterozygous. For instance, say you have two individuals that are both short (S) and have webbed leaves (W) and have the following genotypes.
#1 = SSWW
#2 = SSWw
They are both homozygous for the short trait but only individual #1 is homozygous for the webbed leaf trait. Individual #2 is heterozygous for the webbed leaf trait and would be considered a heterozygous individual. As a goup, they would be considered heterozygous in general by some and homozygous by others. It would depend on your point of reference and the overall importance you place on the webbed leaf trait. Most would consider it to be heterozygous.
For example, the blueberry cannabis strain is considered a true breeding homozygous seed line because as a whole the many offspring have a similar look and produce a similar product. However there are often subtle differences between the plants of characters such as stem colour and potency. When taking a close look at blueberry, you will find heterozygous traits, but because of the whole overall look, we still generally consider them homozygous for the purpose of breeding programs. Using dogs is another way to explain this, take a dobie for example, you cant tell the difference between dobies, but you can tell a dobie from another breed. Ya follow?
Hybrid - An individual produced by crossing two parents of different genotypes. Clarke says that a hybrid is a heterozygous individual resulting from crossing two seperate strains.
- For the purpose of seedbanks, a hybrid is in general, a cross between any two unrelated seedlines. ANY HYBRID IS heterozygous and NOT TRUE BREEDING.
F1 hybrid - is the first generation of a cross between any two unrelated seedlines in the creation of a hybrid. F1 hybrids can be uniform or variable depending on the P1 parent stock used.
F2 hybrid - is the offspring of a cross between two F1 plants (Clarke). What Clarke and other sources don't make clear is do the two F1's need to be from the same parents? By convention they don't. As well, german geneticists often describe a backcross of an F1 back to a P1 parent as a F2 cross.
- OK lets say we take blueberry and cross it with romulan (both relatively true breeding of their unique traits) to create the F1 hybrid romberry. Now lets cross the F1 romberry with a NL/Haze F1 hybrid. (Ed.note:The textbooks consider this a 'double cross'.)
Some could say this is a F1 cross of romberry and NL/Haze. Others could argue that it is a F2 cross of two F1 hybrids. Gets confusing doesn't it? Now lets cross this Romberry/NL/Haze(RNH) with a Skunk#1/NL#5 F1 hybrid to create RNHSN. Now some would argue that RNHSN is an F1 hybrid between RNH and SK/NL seedlines. Others would call it an F2.
- So what does this mean to the consumer? It means that a seed bank can call a cross whatever it wants until the industry adopts some standards. This is what this article will attempt to initiate. Clarke eludes to
standardising these definitions but never really gets around to it. Fortunately other plant breeding communities have (Colangelli, Grossnickle&Russell, Watts, &Wright) and adopting their standards
makes the most sense and offers the best protection to the seedbank consumer.
Watts defines an F1 as the heterozygous offspring between two homozygous but unrelated seedlines. This makes sense and gives the F1 generation a unique combination of traits; uniform phenotype but not true breeding. This is important in the plant breeding world. This means that when a customer buys F1 seeds that they should expect uniform results. It also means that the breeder's work is protected from being duplicated by any other means than using the original P1 (true breeding parents). [There are
exceptions to this by using techniques such as repeated backcrosses (cubing the clone).
F2 crosses are the offspring of crossing two F1 hybrids. This means that they will not be uniform nor will they breed true. However, F3, F4, F5, etc will also share these characteristics, so to simplify terminology for the seedbanks and seedbank merchants, they can all be classified as F2 seeds in general.
What does this mean for the preceeding example? Well, the blueberry, romulan, skunk#1, NL#5, and haze were all P1 true breeding seedlines or strains (another term that needs clarification). Romberry, NL/Haze, and SK/NL were all F1 hybrids. Both the Romberry/NL/Haze and the RNHSN would be F2s. Within each group the consumer can know what to expect for the price they are paying.
Few cannabis seedbanks (if any) and their breeders are following these definitions and are subsequently creating confusion within the cannabis seedbuying community. This is a change that needs to happen.
Note: this is a rough draft to be published to the internet. Hopefully in time it or something similar will be used to help establish an industry standard. Any comments and critism is welcome to aid in the production of the final draft. Small steps like this can only benefit the cannabis community over the long haul.
REFERENCES:
Clarke RC. 1981. Marijuana Botony Ronin Publishing, California
Colangeli AM. 1989. Advanced Biology notes. University of Victoria, BC
Futuyma DJ. 1986. Evolutionary Biology Sinauer Associates, Inc. Massachusetts
Klug & Cummings. 1986. Concepts of Genetics 2nd ed. Scott, Foresman, & comp. Illinois
Grossnickle & Russell. 1989. Stock quality improvement of yellow-cedar. Canada-BC Forest Resources Developement Agreement (F.R.D.A.) Project 2.40
Watts. 1980. Flower & Vegetable Plant Breeding Grower Books, London
Wright JW Introduction to Forest Genetics Academic Press, San Francisco
What is linkage?
Added by: MR_NATURAL420 Last edited by: MR_NATURAL420 Viewed: 989 times
Genes located on the same chromosome are not randomly assorted but tend to be inherited together. This is known as linkage. Plants depend on a large number of factors for their phenotype and linked factors are usually dominant. Linkage adds to the difficulty of combining favorable factors of parents of a cross. Large populations are needed to obtain recombination and find that rare but desirable individual.
(Did you notice UncleBens Pollination method in there?)
