The Cannabis Breeder's Bible (29 page)

X AND Y

As we have seen, cannabis gender can be affected by the environment but initially sex is inherited. Being diploid, cannabis chromosomes are paired. Cannabis has 10 pairs of chromosomes (n=10), for a total of 20 chromosomes (2n=20).

A single pair of chromosomes are responsible for the predetermination of the seed’s sex. The female is X and male is Y, but since they combine as chromosome pairs the genders are set as follows: XX is female, XY is male. There is no YY because the female always contributes an X. The male can either contribute an X or a Y to make up the final pair, XY or XX.

We know that XX means female and XY means male so we should end up with a 50/50 chance of each in the seed produce. However this is not a basis for thinking that all our seeds will be 50% male and 50% female from some seeded bud. Each seed that is being developed has a 50/50 chance, not the overall seeded bud. You could very well produce 99% male seeds. Chances are this will not happen though, and you will probably end up with 50/50, 40/60 or 30/70 amounts.

So seeds can be set genetically with a sexual expression for the plant that will grow from the seed. However we must look more closely at chromosome inheritance to see how the final sexual expression can change from what appears to be set in its genes.

SEX-LINKED TRAITS

Cytology is the science of the structure and functions of the cells of organisms. Two men by the name of Walter Sutton and Theodor Boveri, who worked in this field of study, noticed the comparable factors between Mendel’s work and the chromosome functions. They developed the theory of chromosome inheritance.

A Columbia University researcher named Thomas Hunt Morgan performed experiments that proved that inheritable factors can be sex linked. Morgan chose the fruit fly in his experiments and noted that the fruit fly has only four pairs of chromosomes. Three of these pairs were autosomes (a chromosome other than a sex chromosome) and one pair were sex chromosomes. After years of breeding the flies he noticed a unique male fly in the offspring that had white eyes when all the others had red eyes. He considered that the white eyes were an act of mutation so he decided to breed this male fly.

Morgan bred this white-eyed male with a red-eyed sister and found that whitecolored eyes are sex linked. In the first generation of flies there were only red-eyed offspring, which suggested that the red eye color was dominant and that white eye color was recessive. To prove this Morgan carried on with an F2 generation. With the use of Mendel’s notes he expected that there would be an equal number of males and females with white eyes but this did not happen. All the females had red eyes and only the males had white eyes. Morgan discovered that the white eye color was not only recessive but was also linked in some way to sex.

Morgan knew that a male must inherit the X chromosome from the mother and a Y from the father, so he proposed a connection between the sex chromosomes and the trait for eye color. When the mother was homozygous and had two copies of the gene for red eyes, the male offspring had red eyes, even if the male donor had white eyes. But when the mother had white eyes, the male offspring had white eyes too, even if the father’s eyes were red. In distinction, a female fly gets one X chromosome from each of the parents and if one of the parents passes along an X chromosome with a gene for red eyes the offspring will have red eyes because this allele for color is dominant over white. Only when both parents gave her an X chromosome with a gene for white eyes did she display the recessive trait. Morgan was able to prove that the gene for eye color must reside on the X chromosome that also governs sex. This is a relationship between a specific trait and a specific chromosome. In our case it is called a sex-linked trait.

This is very important to remember in your breeding projects—that traits can be linked together and not only just with sex but with other different genotypes and their expressed phenotypes. Smell and taste may be linked. Bud color and potency may be linked. There are a number of elements that may be linked. It is not understood yet which cannabis traits are linked but maybe in a few years’ time and with a bit more research we can help determine what traits are linked and what traits are not.

DIOECIOUS AND MONOECIOUS PLANTS

Dioecious: Having male and female flowers on different plants.
Monoecious: Having male and female flowers on the same plant.

Most cannabis plants are dioecious, which means that they generate male and female flowers on different plants. This plant type falls into the XX and XY set.

The hermaphrodite condition can be caused by growing conditions and the environment, but there are also types of hermaphrodites that are called monoecious hermaphrodites. These plants are hermie prone and all their offspring show the hermaphrodite trait. They are still mostly diploid plants but the plant’s genes cause the plant to display both sex organs. In this case the hermaphrodite condition can attributed directly to the plant’s genetics and not the environment’s impact.

Apart from haploid or diploid chromosome types there are also triploid and tetraploid sex chromosomes in some plants (which are both polyploid types). These may occur in nature but mostly develop through mutations.The three most common types are:

XXY - triploid.
XXYY - tetraploid.
XXXY - tetraploid.

There are two types of sex-linked traits you should know about. There are “sex limited” linked traits and “sex influenced” linked traits. Sometimes autosomal genes will affect the trait and this is called a sex limited trait. The opposite situation is when sex affects the autosomal genes. This is called a sex influenced trait.

REVERSING THE SEXUAL EXPRESSION OF FEMALES USING SILVER THIOSULFATE SOLUTION

We have already shown you methods of turning male plants into females. Here is a method of inducing the sexual reversal of female to male plants. Always use care when handling these chemicals. Avoid inhaling them by using a dust mask. Always ventilate when using this procedure.

Dutch Passion force a female to turn almost full blown male.

1. Distill some water.

2. Obtain 0.5 grams of Silver Nitrate.

3. Obtain 2.5 grams of Sodium Thiosulfate (Anhydrous).

4. Stir the 0.5 grams of Silver Nitrate into 500ml of the distilled water.

5. Stir the 2.5 grams of Sodium Thiosulfate (Anhydrous) into 500ml of distilled water.

6. Wait 60 seconds for both solutions to dissolve properly. Stir well.

7. Add the Silver Nitrate water solution directly to the Sodium Thiosulfate water solution while stirring rapidly.This produces the Silver Thiosulfate Solution stock.

8. To use this stock on your female plants mix 1 part of the stock to 9 parts water (1:9 ratio).

9. Take this stock mix and put it into a spray can.

10. Spray the entire female plant until the solution appears to be dripping from the plant. Do not do this under lights because bulb heat may alter the chemicals and burn your plant. Do it away from a light source.

11. Let plant dry.

12. As soon as the treated female plant is dry take it back to the grow room and continue 12/12.

13. Store all stock materials and solutions in a fridge.

14. The female will eventually produce male sex organs during flowering. The female organs should not grow anymore, but you may still find some female sexual organs being produced.

Use the sexually reversed female to make feminized seeds or a male donor for females that can only be obtained in clone format. Results may vary from strain to strain. Sometimes plant nutrient deficiency problems may appear such as yellowing on the leaves. This appears to be normal for these treated plants. The plant may also stunt growth initially after treatment for a week or two. Treated plants should not be smoked, eaten or processed in any way. They are simply sexually reversed female plants that can now donate pollen. Never use the spray bottle for anything else other than this treatment.

16

CHROMOSOME MODIFICATIONS IN CANNABIS

AN INTRODUCTION TO CHROMOSOME MODIFICATIONS

The map of the human genome has been completed but the genetic mapping of cannabis is still in the early days yet. We know that if certain chromosomes are altered in plants the effect can be a mutation, but we also know more about what certain chromosome alterations will result in. What follows is a description of some cannabis plant characteristics that have managed to survive in the gene pool with a common noticeable mutated trait.

ANEUPLOIDY

Nondisjunction is a type of mutation that occurs when the chromatids fail to separate. This results in only one gamete receiving two of the same type of chromosome and another gamete receiving no copy. Nondisjunction can result in a number of different mutations. Aneuploidy means “not euploid.” Euploid means “an equal number of all the chromosomes of the haploid set.” Aneuploidy is therefore a condition where abnormal numbers of certain chromosomes are present in an organism. Aneuploid plants result from a normal plant bred with another that has nondisjunction problems. Some aneuploid cell results may even triplicate that chromosome. The aneuploid cell will normally transfer this condition when bred with other normal plants causing serious problems with the offspring’s health and appearance.

We know that this type of condition will affect the plant’s offspring on a large scale while other types of mutations like deletion and translocation are subject to which chromosomes were deleted or how the translocation was newly arranged. Remember that some parts of plant DNA are just in a dormant state and do not appear to do anything while in that dormant state. However we do know that if the effect is not subtle, it may have a profound effect on the plant and its offspring. Sometimes we do not even get to see the effects in the offspring because it renders the plant sterile.

LEAF SPLITTING

Splitting is a very common mutation which results in the splitting of leaves and branches. At the tip of a branch a leaf may develop and then suddenly split into another leaf. The effect looks much like a leaf growing out from another leaf. If you look at the underside of the leaf you will see where the stem and veins have split. This is a common mutation found in Skunk and equatorial cannabis varieties.

On the left, leaf-fusion by EnergyTurtle and on the right a leaf split by strawdog.

TRILATERAL BRANCHING

Trilateral branching is common with South American Sativa strains. Instead of two branches—one at each side of the stem, 180 degrees apart—a third branch develops at the same region but the stem does not split or top itself. The third branch may be on one side or the other, or the three branches may be 120 degrees apart from one another. This popular mutation has picked up the name
whorled phylotaxy
coming from the words
whorl: an arrangement of three or more similar parts or organs at the same level about an axis
and
phylotaxy: The arrangement of leaves or other lateral members on an axis or stem.

Trilaterial Branching (Whorled Phylotaxy) by Mr. Webb.