Read Online The Cannabis Breeder's Bible by Greg Green - Free Book Online
Authors: Greg Green
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our first backcross will result in 50% homozygous (SS) offspring and 50% heterozygous offspring (Ss) for that trait. Here all the offspring will exhibit the pale-green leaf trait. If we didn’t backcross but just used the heterozygous offspring for the breeding program we would have ended up with 25% homozygous dominant (SS), 50% heterozygous (Ss) and 25% homozygous recessive (ss), as shown below.
Backcrossing seriously helps to control the frequencies of a specific trait in the offspring. The F2 hybrid cross produced some plants with the dark-green leaf trait. The F2 backcross did not.
The F2 backcross above is an example of simple backcrossing. Let’s see what happens when we do our second backcross (F3) using the same original parent kept alive through cloning. Our second backcross is referred to as squaring. Since we’re dealing with only two types of offspring Ss and SS, we’ll either repeat the results of the F2 backcross…
…or we will successfully lock down the desired trait as follows:
In the F3 backcross with the homozygote, all of the offspring are homozygous dominant (SS) and thus true breeding for that trait.These offspring are the result of squaring and can never produce the ss traits because the SS trait is now true breeding and stable. The F3 backcross with the heterozygote has some Ss offspring. If we breed the Ss and Ss offspring we can produce the ss trait. This line would not be stable.
HOW TO GENERATE A CLONE MOTHER
The best way to generate a clone mother is to grow a large population of plants from the same strain. If the strain is an IBL then you should find that the plants do not exhibit much variation. It can be difficult to find a clone mother from an IBL strain, though, because IBLs are created to provide a population of plants from seed from the F3 Backcross with the homozygote, which all resemble the clone mother that the breeder enjoyed and wanted to share with you.
The best way to generate a clone mother is to select her from a large population of F1 hybrids. If you do not find a clone mother in the F1 population then allow random mating to occur and see if you can generate a good clone mother in the F2 population. If you do not find the clone mother in the F2 population then either grow a larger population or select different parents to create a new F1 population.
A clone mother is only as good as the environment she is grown in. The environment influences how the genotype is displayed in the phenotype. Although indoor plants can grow outdoors and outdoor plants can grow indoors, the expressed phenotype of the genotype may change because of the diversity in growing conditions. This is why breeders urge that you grow their strains in the recommended environment.
Selfing
Selfing is the ability of a plant to produce seeds without the aid of another plant and refers to hermaphrodite plants that are able to self-pollinate. Hermaphrodite plants have both male and female flowers.This usually means that the hermaphrodite plant is monoecious. Most plants are dioecious and have male and female flowers on separate plants.
Monoecious cannabis strains will always display both sexes regardless of the growing conditions. Under optimal growing conditions a monoecious cannabis strain will still produce both male and female flowers on the same plant. Under optimal growing conditions a dioecious cannabis strain will produce male and female flowers on separate plants.
Stressful growing conditions can cause some dioecious cannabis strains to produce both male and female flowers on the same plant. Manipulating an irregular photoperiod during the flowering stage is an easy way to encourage the dioecious hermaphrodite condition. Not all dioecious cannabis strains can become hermaphrodites. The dioecious cannabis strain must have a preexisting genetic disposition to become hermaphrodite under stressful conditions in order for male and female flowers to appear on the same
Backcrossing seriously helps to control the frequencies of a specific trait in the offspring. The F2 hybrid cross produced some plants with the dark-green leaf trait. The F2 backcross did not.
The F2 backcross above is an example of simple backcrossing. Let’s see what happens when we do our second backcross (F3) using the same original parent kept alive through cloning. Our second backcross is referred to as squaring. Since we’re dealing with only two types of offspring Ss and SS, we’ll either repeat the results of the F2 backcross…
…or we will successfully lock down the desired trait as follows:
In the F3 backcross with the homozygote, all of the offspring are homozygous dominant (SS) and thus true breeding for that trait.These offspring are the result of squaring and can never produce the ss traits because the SS trait is now true breeding and stable. The F3 backcross with the heterozygote has some Ss offspring. If we breed the Ss and Ss offspring we can produce the ss trait. This line would not be stable.
HOW TO GENERATE A CLONE MOTHER
The best way to generate a clone mother is to grow a large population of plants from the same strain. If the strain is an IBL then you should find that the plants do not exhibit much variation. It can be difficult to find a clone mother from an IBL strain, though, because IBLs are created to provide a population of plants from seed from the F3 Backcross with the homozygote, which all resemble the clone mother that the breeder enjoyed and wanted to share with you.
The best way to generate a clone mother is to select her from a large population of F1 hybrids. If you do not find a clone mother in the F1 population then allow random mating to occur and see if you can generate a good clone mother in the F2 population. If you do not find the clone mother in the F2 population then either grow a larger population or select different parents to create a new F1 population.
A clone mother is only as good as the environment she is grown in. The environment influences how the genotype is displayed in the phenotype. Although indoor plants can grow outdoors and outdoor plants can grow indoors, the expressed phenotype of the genotype may change because of the diversity in growing conditions. This is why breeders urge that you grow their strains in the recommended environment.
Selfing
Selfing is the ability of a plant to produce seeds without the aid of another plant and refers to hermaphrodite plants that are able to self-pollinate. Hermaphrodite plants have both male and female flowers.This usually means that the hermaphrodite plant is monoecious. Most plants are dioecious and have male and female flowers on separate plants.
Monoecious cannabis strains will always display both sexes regardless of the growing conditions. Under optimal growing conditions a monoecious cannabis strain will still produce both male and female flowers on the same plant. Under optimal growing conditions a dioecious cannabis strain will produce male and female flowers on separate plants.
Stressful growing conditions can cause some dioecious cannabis strains to produce both male and female flowers on the same plant. Manipulating an irregular photoperiod during the flowering stage is an easy way to encourage the dioecious hermaphrodite condition. Not all dioecious cannabis strains can become hermaphrodites. The dioecious cannabis strain must have a preexisting genetic disposition to become hermaphrodite under stressful conditions in order for male and female flowers to appear on the same
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