Methods to improve breeding of cannabis

merlubroza

merlubroza

Member
I improvement methods, mass selection

Greetings, we will try to explain the first and simplest method of improving plant called mass selection. this method requires a single variety and what is intended in general to improve a characteristic of an ecotype by selection and crossing of the best individuals.

It should first of all take a look at the post of genes and characters of this forum as this type of improvement is used for quantitative traits (which are measured by a number). In particular it increases in such genes are improved additives of a character.
A quantitative trait is controlled by many genes. if for example the height we immediately understood that there are many genes that influence this character.Well the effect is additive to tell us that the greatest amount of additive genes will give us a larger plant.
If a gene is heterozygous additive will give the plant size, if in homozygous plant will give us an even bigger and so for the large number of genes that may regulate the character height for example.

Well the goal of mass selection is to obtain a plant containing the highest number of additive genes for improving the character.
And we are coming more rolls:

The first thing we think is that character that we want to improve and how we will measure it in order to select plants with certain criteria.
In this example we will make a higher plant selection and the variable we will use is the height in centimeters.
the next step is to choose the plant that we want to improve. would be cool if possible a stable ecotype in this case we choose a thai for example.
We planted 125 plants in the same conditions and let them grow up that start to bloom. we measure all the data and pass them to a frequency histogram will give us the typical Gaussian bell. these data we took the mean and standard deviation. (with Excel is a fart).

For example we have a population of plants thai between males and females with an average height of 200cm and a standard deviation of 50cm.
Here we set the selection criteria, remove all plants not exceeding 230 cm and those that do leave to exceed that cross between them.
Once the seeds ripen pick and choose at random 125.
plant them again in the same conditions as the first generation plant and measured when they start to bloom. We put the data into a histogram and took the mean and standard deviation of this new generation. For example in this new generation have an average height of 220cm and a standard deviation of 20 cm.

Well if you get this is that plants are being improved and so this character has what is called heritability. followed as in the first case, selecting plants exceeding 230cm and eliminate those that do not exceed.
allowed to cross and we were with 125 random seeds obtained cycles and so on who want to keep going to slowly fixing the additive genes.

This enhancement method is simple and convenient to do so in ecotype before getting into another method of improving the formation of hybrids. if they were transported to human would select the highest to cross themselves and so prove to expect the highest seed.

Also seen from a different point of view what we are doing is eliminating the lowest.
well then this can be applied to all types of characters: yield, THC, days of flowering, pest resistance, a narrow water ... it all depends on the variable to select, measure and selection criteria.

The selection criteria is important to stay with at least 10% of the total plants because if we were to say 5% (eg if we select taller than 250cm in the example), we are left with very few individuals and we problems of low genetic variability and other hand problems of inbreeding.
 
merlubroza

merlubroza

Member
Methods of improving II. Recurrent selection
We will explain a second method for improving cannabis plants. This method is called recurrent selection and is the
normally used in the stabilization of parental for hybrid formation. The method essentially consists of making crosses of two different plants, evaluate and make crossing the offspring of parents with himself or with descent to stabilize the junction and obtain stable hybrids.

Well first of all should go over some rules of Mendel to understand what is done in such genetically improved. In principle Mendel tells us that in a diploid plant genes found in duplicate and in forming the gametes (pollen or egg) a single gene of the two there pass to them. Thus a plant having two identical gene copies (homozygous) in the gamete assign the same gene with a probability of 1, while a plant having two types of codings (2 alleles, heterozygosity) to pass a same geneof the two in the gamete with a probability of ½ for each allele.
So when we cross two plants can spend 3 things: that the two plants have homozygous and therefore knows for sure what will happen to the offspring to be completely stable for that gene, one of the two homozygotes have the gene and the other heterozygous offspring so will not be so stable that the two plants or the gene present in heterozygous offspring and therefore even less stable.
To this we must add that both parents need not submit the same allele in homozygosis even show it, and two homozygous plants when crossed give a plant with the gene in heterozygous and that what gives a plant is different from whatthat gave the other to the same gene. Well if this happens with a single gene do not even want a plant that has thousands of genes and therefore handling as likely to get us that plants homozygous for all genes is a hard task that would require us to plant millions plants.
Then there is the disadvantage that cannabis is a plant that loves the heterosis and then give us problems of inbreeding and the plant would not go forward.

Well, this is understood, recurrent selection that is tries to get a parent with a high degree of homozygosity for genes from the crossing and get a fairly stable offspring.
The first thing to do is know what we want to improve and have a way to measure it so you can select. In this case and for simplicity choose the height of the plant two months before flowering and will measure in centimeters. It is very important in any improvement project have a grow room with standard conditions to be reproducible and repeatable. In this respect the indoor growing is the best option.

Female parent is chosen to be stable or not (the more stable less labor) and on the other hand the male parent if you need some stability.
Cross and planting the seed (at least 50 plants) and two months is measured their height. These data were removed the mean and standard deviation. Ten plants are selected having a height closer to the average and others are removed.These ten plants flower and go to choose a male, the most beautiful and re-cross with his mother (female parent of our departure). It can be your mother if we have cloned, alternatively it can also serve as his aunt but this would slow the process.
Once the mother crossed with randomly selected 50 seeds and sow. We are left with 2 or 3 girls that are nice and cool and crossed with the first male parent from which we start.
Randomly chose 50 seeds from this cross and planted. Within two months we measured the height of the plants and took the mean and standard deviation.Compared to the first population data we had.
And so on until we get tired ....

It can make all the cycles that they want, the more we will be more stable our plants for height as we are making the female parent crosses with offspring and evaluating the result of crossing with the male parent.
One way we are not only intrinsic stabilizing the height, we are stabilizing the whole plant as this type of improvement increases homozygosity for all genes.The only problem is that it is a process that is a little slow and requires a lot of ground that the illegality of cannabis is a problem.


Well then this is a very good method to stabilize offspring. This or a similar form seed banks draw their seeds. There are other classical genetic methods to obtain parental crosses with large numbers of genes in homozygosis for example by obtaining F2 but is slower and requires more plants to reach the same place.
 
merlubroza

merlubroza

Member
Improvement methods III retocruces


This improvement method we use to improve some feature to a given ecotype.
It is therefore part of a plant type with good agronomic skills we want to transfer some particular feature that has a different ecotype.
The term transfer a feature is very broad and the ease or complexity of the improvement plan will be largely determined by the number of genes that determine the transfer characteristic. On the other hand the success of the breeding program will largely determined by the ability to select individuals for retrocruzarlos obtained.

For these two reasons should inform and be clear about what you want to do before scheduling the improvement method.
Backcross in an improvement plan is to cross to the offspring of one of the parents. When using the backcross usually tries to come to this:

We have a very good plant and therefore has a very interesting combination of genes that we maintain. On the other hand we have a plant that your mediocre or combination of genes not interested in any property unless it has.
When we perform a cross between the two plants the seed takes 50% of their nuclear genetic information from each parent. We want a plant with as much information as one of the parents but to keep the property from the other parent so we crossed to individuals who show the property to be transferred by the parent that we maintain. In this new offspring obtain plants with a 75% to maintain parental genes and 25% of the genes of the plant with the transfer characteristic.What we select are those plants that show this feature and therefore possess the genes that regulate it in that 25% of the parent.
It is so on until you get the parental plants as starting with the characteristic of the other parent.
We will give two examples one controlled by a single gene and another controlled by many genes.


Example 1:

We have a fucking skunk on the other hand we have a orange bud that gives us the hairs of red buds. What we want is to get a skunk with red hair. As we want to get a skunk plant use of the female parent at the first intersection to a skunk, so everything is not nuclear inheritance (cytoplasmic) gave the mother only come from the skunk and it does not interfere with the offspring produced.

Searching for information on the genetics of the coloration of the pistils in plants and indicates that it is a metabolic pathway in which several active enzymes. For information about the segregation of the red cross hairs feature the orange bud itself and offspring shows red hairs in all individuals.

On the other hand we crossed female skunk X male orange bud and vice versa and the progeny of either cross hair shows the red buds. We conducted a cross of the offspring to obtain the F2 of both crosses skunk X orange bud and get two lots in a proportion close to ¼ of females with red hair.

In this previous analysis we get the information that the characteristic red hair is marked by a single recessive gene found in homozygosity in the orange bud original, so that to display in a skunk is to be found also in homozygosis. This type of segregation is typical when a fault enzyme in the metabolic pathway. Being recessive indicates that something is wrong on the road since heterozygous phenotype is restored white hair.



With this information we can design a plan for improvement:
We crossed female skunk X male orange bud. We plant the seed and let it pollinate freely. We obtain F2 seeds that we sow and grow. We eliminate the males. Eliminating females have white hair and we were alone with F2 females with red hair. The skunk crossed with males. We obtain the backcross progeny plant it and let it pollinate itself from which we get the F2 backcross 1. remove the males and females with white hairs. Females with red hair skunk crossed with male retrocruce2 and so get something similar to a plant with red hair skunk. In each backcross offspring get more genes from the skunk.

Example 2: In this example we want to get a plant nepali (susceptible to spider mites) that is tolerant to attack by this pest. The first thing we do is a study of varieties to the attack of red spider. We planted 20 varieties of plants in groups of 5 plants per variety and infect red spider. The most resistant variety as the individual chose to cross the nepali. Normally the tolerance or resistance to pests are determined by many genes.

Given this information we designed the following plan for improvement:
We crossed female for resistant variety nepali male and sow the seed. The descendants we grow and infect red spider. More resistant plants (whether male or female) crossed by the nepali. We plant the seed of the backcross (all together) and infect red spider. Plants more resistant to the cross in a second backcross Nepali ... and so on until Nepali type plants tolerant to attack by red spider.


In short, the backcross can be performed to great multitude of features to give: aroma flavor days of flowering, amount of resin from ... always trying to get a plant and that plant but an acquired characteristic.
 
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