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Old 05-25-2009, 07:05 AM
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Default Overgrows old breeding faqs

Was going through some old stuff and came across this. I figured you guys might like to add it to this section.

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 – The female cannabis plant, unlike the male, is grown to produce marijuana. Premium marijuana is produced in seedless form by eliminating all pollen sources from the growing environment. Seed production reduces the value of marijuana dramatically by lowering the yield and potency of the flowers. Hermaphrodites are plants expressing both male and female flowers. They may fool a grower who mistakes the "hermie" for a female - only to find his crop is ruined by the unexpected release of pollen. Knowledgeable marijuana breeders are very careful to avoid hermaphrodism in their seedlines.

The attributes of a valuable female are the following (in descending order of importance):

1. Resistance to hermaphrodism
2. Vigor/Yield
3. Potency
4. Flavor
5. Rate of flowering response
6. Resin production
7. Stature
8. Scent
9. Floral structure
10. Floral color


Male Cannabis – The male cannabis plant is essentially only useful for breeding. The male plant makes very poor marijuana, being mostly leaves without the dense resinous floral clusters of the female the yield is miserable. More importantly, the male of the species has virtually no potency in comparison to that of female cannabis. The males do carry genes that influence the expression of ALL the traits listed above, but not many of them are directly observable in the male itself due to the male phenotype being markedly different from the female phenotype. A male cannabis plant’s value is DEFINED by the quality of his daughters.

Naturally, when starting out with a large number of potential breeding individuals, one desires to “weed out” the undesirable individuals.

The female is easy to evaluate because all the traits favoring marijuana production are directly observable in the female. It's a simple matter of growing & flowering the females to grade their performance and smoking the resulting marijuana. The breeder then chooses only those females most closely matching the breeder's personal ideal to be used as seed parents.

The directly observable & important traits of male cannabis are as follows:

1. Resistance to hermaphrodism
2. Vigor
3. Stature
4. Maturation rate

All males expressing poor quality in any of these traits should be culled so as not to pass the weak trait on to the progeny.

Males are also be observed to have a certain scent and floral structure but the importance of these traits pale in comparison to those listed.

The potency of male plants, and especially the potency difference between individual males in a group, is generally too subtle to be measured by anything short of professional scientific laboratory equipment. Moreover, there is no conclusive proof that the most potent male in a group actually creates the most potent female progeny, although it seems intuitive that that should be the case. The difficulty of determining a male plant's potency is a major hurdle to proving this link.

Thankfully, logic dictates that the potency of a male plant ITSELF isn’t very important, as we aren’t interested in growing males for marijuana production. The value of a male lies entirely in the traits he consistently passes on to his daughters. Therefore it’s unnecessary to identify the one male amongst a group of potential pollen donors with the greatest potency. It’s far more logical to evaluate the female progeny of each male to define the potency of each male in the group.

Male cannabis individuals may be graded for quality by a controlled pollination of IDENTICAL female clones (one for each pollen donor). This isolates the influence of the male by holding CONSTANT the influence of the female on each cross. The seeds resulting from each clone are then grown and the progeny is graded to determine which of the crosses was the most successful. When the group with the most desirable female progeny is identified, the responsible male has been identified as the most valuable. Males can be kept in the vegetative state exactly like female “mother plants”, except that we should call them “dads” of course. Clones from the favored male can be flowered as needed along with the breeding female(s) when seeds are desired.

Due to the clandestine nature of marijuana growing, in most cases there will only be about 10 males to be evaluated after culling all those with directly observable defects. Breeding with larger populations is always preferable, as genetics is a statistical "game".

Commercial breeders would clearly benefit from the development of a reliable method of identifying males with the greatest potential for passing on high potency genes. Perhaps someone will do the necessary research someday, but by following the above method, growers can accurately pin-point the ONE male in their small group which is the most potent...in the only meaningful sense of “male potency”.
What are all female seeds and how are they created?
Added by: ~shabang~ Last edited by: ~shabang~ Viewed: 2178 times
Contributed by Mr.XX and TheSiliconMagician:

This is the strategy of Mr. XX, a Dutch breeder, for creating all female seedlines from slight hermaphroditic pollen. What he does is put the lights on 12/12 for 10 days. Then turns the lights on 24 hours, then 12/12 again for a few days, then back to 24 hours for a day, then 12/12 again for a few weeks.

If he does this and no hermaphrodites come up. He has found a 100% XX female that cannot go hermaprhoditic naturally. He says that your chances of finding a 100% XX female is vastly increased when using Indica genetics. He told me that the more Afghanni or Nepalese genetics the plant has, the better the chances of finding a natural XX female. His
exact words were "Where did mother nature give weed a home at originally?"

I tried to get him to narrow it down to a ratio, but he never specified just how many plants per are XX females his exact words are "plenty of XX girls for everybody" and that is all he will say on the subject. Only that it takes alot of time and alot of plants to find that one female.

He then uses Gibrellic acid. 30 centiliters of water with 0.02 grams of Gibrellic acid and 2 drops of Natruim Hydroxide to liquify the Gibrellic. Then applies as normal and creates the male flowers. He has gotten down to the 4th Generation with NO loss of vigor, NO genetic deficiencies and NO hermaphrodites. He claims that the plants are EXACT GENETIC CLONES of one another. Complete sisters. Basically it's clone from seed instead of from normal cloning methods.
How do I create a true breeding strain?
Added by: ~shabang~ Viewed: 1869 times
Contributed by Vic High:

I've been hearing a fair bit of confusion from many on how to create a true breeding strain and so I'm writing this page to try and help shed some light on the subject. There are a few situations where a plant breeder would want to create a true breeding strain (IBL) and a few ways of accomplishing the task. But understanding the subtle differences of the various techniques is not so easy. This paper will attempt to give a basic understanding of what is actually happening with each technique and then apply what is learned to actual projetcs. As a friend worked overtime making sure I didn't forget, breeding is not a black and white subject and as a whole, it would be too complex to put on paper in an easily understood form. Therefore, I will create small fictional examples to reinforce various concepts and then we will take those examples and concepts and apply some reality to them. Try not to get hung up on the erroneous assumptions used here such as flavour being monogenic, the assumption is simply used to make it easier to learn a certain concept.


Just What Is It That We Are Doing?

Before we dive in, maybe we should take the time to understand what we are trying to accomplish when we set out to create a true breeding strain. There are hundreds of possible phenotypic traits that we could observe within a cannabis population. Are we trying to make all of them the same and remove ALL variation? Not likely, the genetic code is just too complex to try. Plus, since phenotype (what we see) is 1/2 genotype + 1/2 environment, everytime the population was grown under new conditions, new heterozygous traits would be observed. Basically, all we are trying to create is an overall uniformity while not worrying about the minor individual variations. No different than a dog breed. You can look at a german shepard and recognise it as belonging to a discrete breed. But if you look closer at several german shepards all at the same time, you will find variations with each and every one of them. Some will be a little taller, some a little wider, some more agressive, some a little fatter, some darker, etc. But they would all fall within an acceptable range for the various traits. Generally speaking, this is what a plant breeder is trying to accomplish when creating a true breeding strain, or IBL.

However this isn't always the case. Sometimes a breeder will just concentrate on a specific trait, like say outdoor harvest date, or mite resistance. You could still have a population where some are 2' bushes and some 10' trees. In this case, you would say that the strain was true breeding for the particular trait, but you wouldn't consider it true breeding strain per se. In genetics, wording plays a big part in meaning and understanding. As does point of reference as my F1 vs F2 comparison page illustrates.

Ok, so we want to make a cannabis population fairly uniform over a few phenotypically important traits, like say flavour for instance. For simplicity sake, we'll just deal with the single trait flavour, it's complex enough. And although flavour is controlled by several gene pairs (polygenic), we'll make the simplistic assumption that it's controlled by a single gene pair (monogenic) for many of the models and examples in this paper. There are many flavours such as chocolate, vanilla, musky, skunky, blueberry, etc, but in this paper we'll just deal with two flavours, pine and pineapple. Either gene in the gene pair can code for either of the flavours. If both genes code for pineapple or both genes code for pine flavour, we say that the gene pair (and individual plant) is homozygous for flavour. If the one gene codes for pine and the other codes for pineapple, we say that the gene pair (and individual plant) is heterozyous with respect to flavour. The heterozygous individual can create gametes (pollen or ovules) that can code for either pine flavour or pineapple flavour, the homozygous individuals can only create gametes that code for one OR the other. A homozygous individual is considered true breeding and a heterozygous individual is not.

However, as the words imply, when we are creating a true breeding strain, we are looking at a population, not individuals. We are trying to make all the individuals in the population homozygous for a particular trait or group of traits. Lets say we have a population of 50 individual plants, and each plant has has a gene pair coding for flavour. That means that 100 flavour genes make up the flavour genepool (reality is much more complex). When trying to create a true breeding strain, we are in fact trying to make all 100 of those genes code for the same trait ( pineapple flavour in our case). The closer our population comes getting all 100 genes the same, the more homozygous or true breeding it becomes. We use the terminology gene frequency to measure and describe this concept, where gene frequency is simply the ratio or percentage of the population that actually contains a specific gene. The higher the gene frequency, the more true breeding the population is. A fixed trait is where the gene frequency of the trait reaches 100%.

And folks, this is the basic backbone of what breeding is all about, manipulating gene frequencies. It doesn't matter if your making IBL, F1s, F2s, selecting for this or selecting for that, all you are really doing is manipulating gene frequencies. Therefore, to ever really understand what is happening in any breeding project, the breeder must pay attention to gene frequencies and assess how his selective pressures and models are influencing them. They are his measure of success.


What are we trying to create a true breeding strain from?

This a good question. Sometimes a gardener will notice a sport or unique individual in an F2 population, like say it has pineapple flavour when the rest have pine flavour. For one reason or another he decides he wants to preserve this new trait or combination of traits from that single individual. For the sake of ease of comprehension, we tend to call this special unique individual the P1 mom. He could start by selfing the individual OR breeding that individual with another and create what can be described as F1 offspring. If the F1 route was chosen, then breeders can diverge down two new paths. Some breeders will take the progeny of the F1 crossing and breed it back to the P1 mom, and then repeat for a couple more generations. This is referred to as backcrossing or cubing by cannabis breeders. Another common strategy is to make F2 progeny from the F1 population and then look for individuals that match the P1 mom. They would repeat the process for a few generations. We can call this filial or generational inbreeding since the parents from each cross belong to the same generation.

In another situation, sometimes a farmer will notice a few individuals in his fields that stand out from the crowd in a possitive manner. Like say the are resistant to a problem pest like powdery mildew. In this case, he will collect the best of the individuals and his starting population will contain several similar individuals and not a unique single individual as in the previous example. He would skip the hybridizing step (making the F1s) and go straight to the generational inbreeding step. Links to pages going into detail of each of these basic techniques and their impact on influencing gene frequencies are at:

A) Selfing the individual

B) Backcrossing and Cubing

C) Filial or Generational Inbreeding from an individual

D) Filial or Generational Inbreeding from a group


Applying the Pressure
Another excellent method to influence gene frequencies is to apply selective pressure. The idea here is to select only individuals that carry the desireable genes, and discard the rest.


A) Principles of selection
B) Progeny tests

How do I backcross my special female?
Added by: ~shabang~ Last edited by: ~shabang~ Viewed: 1637 times
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).

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.
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Old 05-25-2009, 07:06 AM
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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’ve used borrows from the “cubing a clone” technique. This is the technique of mixing pollen from all the selected males. This method guarantees that from the very first group of seedlings, a predefined fraction will be the offspring of the best male plant (defined as the male responsible for creating the best daughters). They will be easy to identify, being the superior plants.

The disadvantage of this method is that the identity of the responsible male is lost, rendering that specific cross difficult to repeat. That’s a major disadvantage if the intention were commercial production of the hybrid strain. However because it’s more time-saving & practical, mixing the pollen is the best method for home breeders wishing only to obtain a great clone mother. One need only germinate a large enough group of seeds to ensure several female offspring of each select male & the future clone mother will be among them.

Consider Cubing:

Cubing a clone is a way to create a unique seedline (a “strain”) modeled after a currently existing female individual. The goal is to create seeds from which the females replicate the phenotype of the original female. Obviously the chosen female should be an outstanding specimen.

Procedure:

CONTINUOUSLY KEEP A MOTHER IN THE VEGETATIVE STATE TO PROVIDE CLONES

1. Pollinate a flowering clone of the original female with the pollen of a related male, preferably her father or a brother. The resulting seeds contain 1/2 the original female's genes and 1/2 those of the male. An unrelated male won’t have the Y-chromosome of the chosen female’s family & therefore any Y-linked traits of the family will always be missing in the seedline.

2. Grow the above seeds & flower them. Collect an equal quantity of pollen from each selected male and mix it together.

3. Pollinate a flowering clone of the original female with the above pollen. These seeds contain 1/2 the original female’s genes plus 1/4 more because the male used was 1/2 her genetics too. I call this generation “.75” to capture the idea that it’s 3/4 of the original female’s genetics.

4. Grow the above seeds & flower them. Collect an equal quantity of pollen from each selected male and mix it together.

5. Pollinate a flowering clone of the original female with the above pollen. These seeds contain 7/8 the original genes (1/2+3/8), the ".88" generation.

6. Grow the above seeds & flower them. Collect an equal quantity of pollen from each selected male and mix it together.

7. Pollinate a flowering clone of the original female with the above pollen. These seeds contain 15/16 the original genes (1/2+7/16), the ".94" generation. Theoretically this will be a stable, true-breeding seedline from which all females are replicas of the original.

Note that in cubing we have no further use for the males of previous generations after taking their pollen. Therefore mixing the pollen & losing the identity of “best male” is no problem here. The goal of the cubed strain is to reproduce the female phenotype, independent upon P1 generations for reproduction after a certain number of steps in the cubing process.

I recommend carefully evaluating the females produced in each generation of the cubing process to monitor their progress. If the results don’t progressively shift toward your goals, then you may have to change your male selection parameters.
What is selfing?
Added by: ~shabang~ Last edited by: ~shabang~ Viewed: 1106 times
Contributed by Vic High:

As the title implies, the main drawback to selfing cannabis plants is that you loose the male portion of your population, making future crosses difficult. Some think that by selfing a plant, all the offspring will turn out just like mom. That is only true if mom is true breeding for all the traits you are interested in. Otherwise, her offspring will show two phenotypes for every trait that she is not true breeding.

There are two basic models for selfing a plant such as cannabis the first one being where the plant is homozygous for the trait in question. Let's assume again that pineapple flavour is controlled by the recessive gene pp. If we self the plant we fill get the following S1 cross.

S1 cross = pp x pp = pp + pp + pp + pp or 100% pineapple flavoured female offspring. But no matching males

The other likely possibility is that special individual heterozygous dominant for the pineapple flavour. In this case P will indicate for pineapple flavour and the S1 cross will be:

S1 cross = Pp x Pp = PP + Pp + Pp + pp, our familiar 1:2:1 mendelian ratio.

In this second example only 75% of the offspring will have pineapple flavour and the frequency of the P gene will only be 50%, a far cry from 100% or true breeding. From here on, this isn't much different from a half sib cross involving regular inbreeding or backcrossing. It will take a few generations to achieve something close to true breeding, but as with backcrossing, as long as we use the P1 mom in the crosses (selfing in this case), we will never achieve a true breeding population.
What is recurrent selection?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 908 times
Recurrent selection refers to selecting for certain traits generation after generation.

With the interbreeding of reselected plants, the breeder can access favorable recombinations as well as stabilize traits within the genepool. Select your ideotype in each IBL, but don't be totally reliant on the phenotype because its not always indicative of the actual genotype. Make yield and quality trials with test crosses and select the best ten lines. Intercross and repeat.

After recurrent selection is done, select new individuals to be the new parents of IBLs. These are then recurrently selected for four or five generations. After recurrent selection has been done in two seperate programs, an F1 single cross of the two lines (A X B) is then produced.

In reciprocal recurrent selection (RRS), pollen of multiple A males is used to pollinate ideal B females and pollen of B used to pollinate ideal plants of A. Thus A is used as a tester to select for the combining ability of B plants, and B is a tester for A. At the same time,inbred seedlots(A X A) and (B X B) are made,using mixed male pollen and the best females of each population. Store the resulting seed-- the seedlines with the best combining ability will be used as parents of the next RRS cycle.

The (A X B) hybrid progeny are simply used as visual indicators of the combining ability that lies in the saved seeds.These specific inbred parental lines are kept in reserve until the progeny testing of the different (A X B) hybrids has shown which has better SCA and will make the better hybrids. Since this is such a complicated strategy, good note taking and organization are definitely required.
What is convergent improvement?
Added by: MR_NATURAL420 Last edited by: Team GrowFAQ Viewed: 654 times
If you have a good single cross (A X B), and you know the vigour is the result of the dominance of growth factors, back-cross it several generations to A, selecting for qualities of B that are lacking in A. After two or more generations of back-crossing and selecting, IBLs are produced. Do the same for B. After improved A and B are obtained, they are tested in crosses and compared to the original (A X B).

Multiple convergence is improving an inbred by convergence of gametes from different sources. If A is a very desirable inbred in crosses, it can be modified in two seperate back-cross programs {eg. (A X C) X A, and (A X D) X A}, with the idea that the improved inbreds will be vigourous enough to use as the male parent of a double-cross.

How important is male selection when cubing?
Added by: ~shabang~ Last edited by: ~shabang~ Viewed: 653 times
Contributed by Vic High:

Basically, when you are cubing a mother plant, you are taking her paired alleles and making them homozygous for each trait that you want to become true breeding. Some paired alleles will already be homozygous but most of the important ones will be heterozygous in the case of an F1 other-to-be-cubed. Mind you this can only be true of those traits that are controlled by basic dominant/recessive genes. This isn't always the case and sometimes genes can be codominant. Here is an example of the implications.

let A & B & C be codominant genes, d being a recessive gene on the same loci. Now for simplicity we will just look at the genotype and ignore the phenotypic effects of each genotype. Lets say our mother-to-be cubed has the genotype AB and the P1 male is Cd (both being F1s).

Notice that you can never really get a completely true breeding situation with this sort of gene. To fully capture the mother's trait you must maintain the heterozygoous AB condition. Crossing two parents with the same characteristic AB will give the following offspring:

AA, AB, AB, BB

Note only 50% of the offspring will ever be able to recreate this mother's genotype (and in this case phenotype)

Ok, now that aside, lets explore the practical issues of trying to cube that mom. Crossing the AB and Cd you the following combinations:

AC, Ad, BC, Bd. You then select from these to do your first backcross to your AB mom (creating the .75 generation)

ABxAC = AA, AC, AB, CA - 25% resemble mom in this case
ABxAd = AA, Ad, AB, Bd - 25% resemble mom again
ABxBC = AB, AC, BB, BC - 25% resemble mom again
ABxBd = AB, Ad, BB, Bd - 25% resemble mom again

As you can see, it really doesn't matter which males you selected for your first backcross as they all brought you equally close to your goal. Notice that it will also take a sharp eye to pick out the special offspring that will take you closer to your goal in the second backcross. Hopefully this shows how difficult it can be to stabililize a trait caused by codominant genes.

This was just the first factor affecting cubing success. Also, it only dealt with a single genes and you are often trying to stabilize dozens of gene pairs when cubing.
What is an F1, F2, and IBL?
Added by: MisterIto Last edited by: Team GrowFAQ Viewed: 4301 times
An IBL (inbred line) is a genetically homogeneous strain that grows uniformly from seed.

A hybrid is a strain made up of two genetically unlike parents, IBL or hybrid.

When you cross two different IBL strains for the FIRST time, it is called the F1 generation. When you cross two of the same F1 hybrid (inbreed), it is called the F2 generation.

The process of selective inbreeding must continue at least until the F4 to stabilize the recurrently selected traits. When you cross two specimens of an IBL variety, you get more of the same, because an IBL is homozygous, or true breeding for particular traits.
How should I store my seeds?
Added by: MisterIto Last edited by: ~shabang~ Viewed: 3447 times
For uninterrupted long term storage, freezing in a vacuum pack with a dessicant is best. Each time a batch of seeds goes through a freeze/thaw cycle, a few become unviable. For storage lengths of a few years or less, room temperature storage in an airtight container with a dessicant is satisfactory. Vacuum packing with dessicant and room temperature storage is best for access without the thaw and re-freezing that kills them. The problem with using the refrigerator for any period of time is the excessive amount of moisture constantly present. Each time the door is opened, moisture condenses on items inside, for which the dessicant is an inadequate deterrent for molds. A vacuum sealed container should not condense moisture on the inside. Using heat to remove any moisture present in rice or other "makeshift" dessicants will improve effectiveness and longevity. I have heard of vermiculite being used as a dessicant, but would recommend silica gel as a first choice. I heard of properly stored seeds over 10 years old still germinating at acceptable rates.
What is colchicine and how is it used?
Added by: ~shabang~ Last edited by: Team GrowFAQ Viewed: 3178 times
Contributed by PAXCO:

Polyploidy (favorable traits in Cannabis) has not been shown to occur naturally in Cannabis; however, it may be induced artificially with colchicine treatments. Colchicine is a poisonous compound extracted from the roots of certain Colchicum species; it inhibits chromosome segregation to daughter cells and cell wall formation, resulting in larger than average daughter cells with multiple chromosome sets.

The studies of H. E. Warmke et al. (1942-1944) seem to indicate that colchicine raised drug levels in Cannabis. It is unfortunate that Warmke was unaware of the actual psychoactive ingredients of Cannabis and was therefore unable to extract THC. His crude acetone extract and archaic techniques of bioassay using killifish and small freshwater crustaceans are far from conclusive. He was, however, able to produce both triploid and tetraploid strains of Cannabis with up to twice the potency of dip- bid strains (in their ability to kill small aquatic organisms). The aim of his research was to "produce a strain of hemp with materially reduced marijuana content" and his results indicated that polyploidy raised the potency of Cannabis without any apparent increase in fiber quality or yield.

Warmke's work with polyploids shed light on the nature of sexual determination in Cannabis. He also illustrated that potency is genetically determined by creating a lower potency strain of hemp through selective breeding with low potency parents. More recent research by A. I. Zhatov (1979) with fiber Cannabis showed that some economically valuable traits such as fiber quantity may be improved through polyploidy. Polyploids require more water and are usually more sensitive to changes in environment. Vegetative growth cycles are extended by up to 30-40% in polyploids. An extended vegetative period could delay the flowering of polyploid drug strains and interfere with the formation of floral clusters.

It would be difficult to determine if cannabinoid levels had been raised by polyploidy if polyploid plants were not able to mature fully in the favorable part of the season when cannabinoid production is promoted by plentiful light and warm temperatures. Greenhouses and artificial lighting can be used to extend the season and test polyploid strains. The height of tetraploid (4n) Cannabis in these experiments often exceeded the height of the original diploid plants by 25-30%. Tetraploids were intensely colored, with dark green leaves and stems and a well developed gross phenotype. Increased height and vigorous growth, as a rule, vanish in subsequent generations. Tetraploid plants often revert back to the diploid condition, making it difficult to support tetraploid populations. Frequent tests are performed to determine if ploidy is changing.

Triploid (3n) strains were formed with great difficulty by crossing artificially created tetraploids (4n) with dipbids (2n). Triploids proved to be inferior to both diploids and tetraploids in many cases. De Pasquale et al. (1979) conducted experiments with Cannabis which was treated with 0.25% and 0.50% solutions of colchicine at the primary meristem seven days after generation. Treated plants were slightly taller and possessed slightly larger leaves than the controls, Anoma- lies in leaf growth occurred in 20% and 39%, respectively, of the surviving treated plants. In the first group (0.25%) cannabinoid levels were highest in the plants without anomalies, and in the second group (0.50%) cannabinoid levels were highest in plants with anomalies.

Overall, treated plants showed a 166-250% increase in THC with respect to controls and a decrease of CBD (30-33%) and CBN (39-65%). CBD (cannabidiol) and CBN (cannabinol) are cannabinoids involved in the biosynthesis and degradation of THC. THC levels in the control plants were very low (less than 1%). Possibly colchicine or the resulting polyploidy interferes with cannabinoid biogenesis to favor THC. In treated plants with deformed leaf lamina, 90% of the cells are tetraploid (4n 40) and 10% diploid (2n 20). In treated plants without deformed lamina a few cells are tetraploid and the remainder are triploid or diploid.

The transformation of diploid plants to the tetraploid level inevitably results in the formation of a few plants with an unbalanced set of chromosomes (2n + 1, 2n - 1, etc.). These plants are called aneuploids. Aneuploids are inferior to polyploids in every economic respect. Aneuploid Cannabis is characterized by extremely small seeds. The weight of 1,000 seeds ranges from 7 to 9 grams (1/4 to 1/3 ounce). Under natural conditions diploid plants do not have such small seeds and average 14-19 grams (1/2- 2/3 ounce) per 1,000 (Zhatov 1979). Once again, little emphasis has been placed on the relationship between flower or resin production and polyploidy. Further research to determine the effect of polyploidy on these and other economically valuable traits of Cannabis is needed.

Colchicine is sold by laboratory supply houses, and breeders have used it to induce polyploldy in Cannabis. However, colchicine is poisonous, so special care is exercised by the breeder in any use of it. Many clandestine cultivators have started polyploid strains with colchicine. Except for changes in leaf shape and phyllotaxy, no out- standing characteristics have developed in these strains and potency seems unaffected. However, none of the strains have been examined to determine if they are actually polyploid or if they were merely treated with colchicine to no effect.

Seed treatment is the most effective and safest way to apply colchicine. * In this way, the entire plant growing from a colchicine-treated seed could be polyploid and if any colchicine exists at the end of the growing season the amount would be infinitesimal. Colchicine is nearly always lethal to Cannabis seeds, and in the treatment there is a very fine line between polyploidy and death. In other words, if 100 viable seeds are treated with colchicine and 40 of them germinate it is unlikely that the treatment induced polyploidy in any of the survivors. On the other hand, if 1,000 viable treated seeds give rise to 3 seedlings, the chances are better that they are polyploid since the treatment killed all of the seeds but those three.

It is still necessary to determine if the offspring are actually polyploid by microscopic examination. The work of Menzel (1964) presents us with a crude map of the chromosomes of Cannabis, Chromosomes 2-6 and 9 are distinguished by the length of each arm. Chromosome 1 is distinguished by a large knob on one end and a dark chromomere 1 micron from the knob. Chromosome 7 is extremely short and dense, and chromosome 8 is assumed to be the sex chromosome. In the future, chromosome *The word "safest" is used here as a relative term.

Colchicine has received recent media attention as a dangerous poison and while these accounts are probably a bit too lurid, the real dangers of exposure to coichicine have not been fully researched. The possibility of bodily harm exists and this is multiplied when breeders inexperienced in handling toxins use colchicine. Seed treatment might be safer than spraying a grown plant but the safest method of all is to not use colchicine. mapping will enable us to picture the location of the genes influencing the phenotype of Cannabis. This will enable geneticists to determine and manipulate the important characteristics contained in the gene pool. For each trait the number of genes in control will be known, which chromosomes carry them, and where they are located along those chromosomes.

(Taken from 'Marijuana Botany',R.C.Clarke,CH.3)

What is the difference between an F1 and a hybrid?
Added by: ~shabang~ Last edited by: Team GrowFAQ Viewed: 3024 times
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

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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.
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Old 01-19-2010, 07:36 PM
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learn something new every day man. Thanks very much for the post!! super-informative and extremely interesting
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