Marijuana strains are either pure breeds or hybrid varieties of Cannabis, typically of the species C. indica or C. sativa. Strains are developed to highlight a specific combination of properties of the plant or to establish marketing differentiation. Strain names are typically chosen by their growers, and often reflect properties of the plant such as taste, color, smell, or the origin of the strain.
Clone-only strain – A cannabis grower may grow a cannabis seed into a plant and find that this plant is unique in some way. The grower may make genetically identical clones of the plant and distribute these. A clone is the only way to propagate the exact genetic makeup that makes a strain unique, however, growing conditions greatly affect the plant and the final consumable product.
Stable seed strain – For a cannabis breeder wishing to develop a new strain, the process is complicated and time consuming. It involves selectively choosing male and female cannabis plants and breeding them over the course of multiple generations. The final generation’s seeds will be stabilized by the breeder on the specific attributes chosen, though some genetic variation still exists among the seeds.
Unstable seed strains – While these can be produced more quickly, plants grown from these seeds may have widely varying characteristics. Reputable seed shops will not distribute unstable seed strains, though some amateur growers might. Third-party growers may produce unstable derivatives from well known strains and misleadingly call them by their true strain name.
Wild strains (Landraces) – Some strains, such as Colombian and Thai refer to cannabis plants found growing wild in certain regions. Typically, these plants are used as bases for the production of more specialized strains (e.g. G-13 or Haze).
Additionally, black market Cannabis dealers may distribute marijuana that is misleadingly called by a strain name. For example, (Skunk and G13) may be used, but a lower grade is actually be sold.
In addition to “pure” indica, sativa, and ruderalis strains, hybrids strains with varying ratios of these three types are common. For example, the White Widow hybrid is purported to have about 60% “indica,” and 40% “sativa” genetics. These hybrid strains have combinations of traits derived from both parental types. There are also commercial cross-bred hybrids which contain a mix of both ruderalis, indica and/or sativa genes (these hybrids are usually called autoflowering strains). “Lowryder” is the most famous auto-flowering hybrid and retains the auto-flowering characteristic of ruderalis plants, while also producing usable amounts of THC/CBD. Auto-flowering marijuana strains are considered advantageous by some growers due to their discreet size, short growing periods, and the fact that they do not rely on a change in light schedule to determine when to flower.
Strains are often named by the breeder or grower to differentiate one from another. In competitive legal markets, such as in Amsterdam, there is significant pressure to create unique strains that dominate the market. This results in a number of distinct strain names that may refer to very similar cannabis.
Likewise, when a strain becomes popular, many breeders and growers may produce variations of the same strain using the same or similar name.
Breeding involves pollinating a female cannabis plant with male pollen. This will happen naturally. However, the intentional creation of new strains typically involves selective breeding in a controlled environment.
The seeds produced by a germinated female will be F1 hybrids of the male and female. These offspring will not be identical to their parents. Instead, they will have characteristics of both parents. Advanced techniques can stabilize certain characteristics.
A common technique to stabilize a cannabis strain is called “cubing”, in which the breeder will seek specific traits in the hybrid offspring (e.g. greater resin production, tighter node spacing, etc.) and breed said offspring with a parent plant. The same traits are sought in the new inbred offspring, which are then bred back again with the original parent plant. This process called cubing because it is usually repeated across three (or possibly more) generations before a strain can be considered at least somewhat stable.
Seed shops sell both pure strains that have specific aspects stabilized as well unstabilized hybrids that may be of questionable quality.
Marijuana can be propagated either sexually or asexually. Seeds are the result of sexual propagation. Because sexual propagation involves the recombination of genetic material from two parents we expect to observe variation among seedlings and offspring with characteristics differing from those of the parents. Vegetative methods of propagation, cloning, cuttage, layerage, or division of roots are asexual and allow exact replication of the parental plant without genetic variation. Asexual propagation, in theory, allows strains to be preserved unchanged through many seasons and hundreds of individuals
When the difference between sexual and asexual propagation is well understood then the proper method can be chosen for each situation. The unique characteristics of a plant result from the combination of genes in chromosomes present in each cell, collectively known as the genotype of that individual. The expression of a genotype, as influenced by the environment, creates a set of visible characteristics that we collectively term the phenotype. The function of propagation is to preserve special genotypes by choosing the proper technique to ensure replication of the desired characteristics.
Cannabis hybrids are medical marijuana strains that have been cross bred. You can cross an indica and a sativa and get an indica/sativa mix. Breeders try to select the best attributes of each strain and create a new strain that is the best of both worlds.
Hybrid cannabis strains are a mix of strains. Example:
Hybrid cannabis strains are the favorites of all pot growers because of enormous THC levels and different plant characteristics growers can manipulate. Breeders take the best of the indica world such as high CBD levels and breed that with the best of the sativa world such as high THC levels, now you have developed strong, super pot. Another genetic trait to consider when breeding hybrid cannabis is the indica bush and the sativa long stems to produce a larger yielding plant. Flavors of sweet indica are blended with the fruity taste of sativa to produce new exciting berry flavors of smoke.
White widow being the most famous hybrid cannabis strain could perhaps be the most potent of all. Now growers can choose from cannabis strains that are better suited for outdoor or indoor gardens. A good sativa can have its growth period reduced by cross breeding with a fast flowering outdoor indica like a Master Kush and Northern Lights.
Most of the marijuana pictures below are the result of extensive breeding, and creation of hybrids by interbreeding of marijuana plants with the desired characteristics. Each generation of plant builds on the characteristics of its parents.
It can take many generations to acquire the desired features. Some of the well known Amsterdam seed suppliers are reputed to breed a thousand plants at a time, pick the best fifty plants, breed them with each other, then start the process all over again with another thousand plants of the new genetic mix.
Marijuana plants inherit their genetic characteristics from their sets of parents. Natural heredity laws define why offspring inherit different traits from the same parents. These laws assist breeders to forecast the number of offspring that stand to inherit a specific trait. Anyone who is serious about breeding must have a good background in the laws of heredity. It is essential.
Inbreeding establishes a pure breed. A pure breed has consistent chromosomes. That is, the genetic makeup of offspring is relatively uniform. This true or pure breed is necessary so common growth characteristics may be established. If the plants are not a pure breed, it will be impossible to predict the outcome of the hybrid plant. After the fourth, fifth, and sixth generation of inbreeding occurs, negative characteristics, like low potency, legginess and lack of vigor tend to dominate. Inbreeding is necessary to establish a true breed, but after that, stay away from inbreeding!?
“Hybrid” simply means the parents were of two different strains. Most cannabis seeds sold today are hybrid strains. There exists in some areas a few native strains, for instance, in Jamaica, the primary type is a sativa called ‘Haze.’ ‘Kush’ comes from the mountains of the Hindu Kush, and ‘Durban Poison’ comes from Africa.
It is not only sativa/indica crosses, but it can be two different strains of the same type. For instance, ‘White Russian’ is a cross of ‘White Widow’ (indica) and ‘AK-47’ (sativa). ‘Crystal’ is a cross of ‘White Widow’ (indica) & ‘Northern lights’ (indica)
The advantages to hybrids are generally in their size and the length of time to harvest. Indicas are generally smaller and finish earlier, so crosses are often made with Sativas in order to shorten both. The type of high is different between the types as well, so crosses are made to combine the best of both. User preferences also differ, and offspring of hybrid breedings are selected based on preference for further propagation.
The disadvantages are that hybrid strains often do not breed “true” and results of a cross may be any number of different types (phenotypes) of plants from the same parents. It is for this reason that the seeds from the best plants resulting from a mixed breeding are often then grown out and bred to each other to produce a more stable strain that will breed truer over several generations.
In 1998 the Dutch Passion company made a major breakthrough in marijuana seed technology through the development of feminized marijuana seeds. Hybrid is a term used to describe marijuana plant offspring produced by crossbreeding two different ‘true-breeding’ parents. True-breeding marijuana plants will produce true to type if reproduced from their own seeds, so different generations will share similar characteristics. True-breeding strains are either (1) Pure-Breeds: traditional land races that have only interbred with similar strains and so have almost identical genes or (2) Stabilized Hybrids: hybrids that have been created by breeders but then continually inbred until their marijuana plant characteristics are stabilized from generation to generation. F1 denotes that the seeds or marijuana plants have two true-breeding parents. The crossing of marijuana genetics produces marijuana plants whose characteristics will not be the same as the original true-breeding marijuana parents, though they may share many characteristics or qualities.
All of the Cannabis grown in North America today originated in foreign lands. The diligence of our ancestors in their collection and sowing of seeds from superior plants, together with the forces of natural selection, have worked to create native strains with localized characteristics of resistance to pests, diseases, and weather conditions. In other words, they are adapted to particular niches in the ecosystem. This genetic diversity is nature’s way of protecting a species. There is hardly a plant more flexible than Cannabis. As climate, diseases, and pests change, the strain evolves and selects new defenses, programmed into the genetic orders contained in each generation of seeds. Through the importation in recent times of fiber and drug Cannabis, a vast pool of genetic material has appeared in North America. Original fiber strains have escaped and become acclimatized (adapted to the environment), while domestic drug strains (from imported seeds) have, unfortunately, hybridized and acclimatized randomly, until many of the fine gene combinations of imported Cannabis have been lost.
Changes in agricultural techniques brought on by technological pressure, greed, and full-scale eradication programs have altered the selective pressures influencing Cannabis genetics. Large shipments of inferior Cannabis containing poorly selected seeds are appearing in North America and elsewhere, the result of attempts by growers and smugglers to supply an ever increasing market for marijuana. Older varieties of Cannabis, associated with long standing cultural patterns, may contain genes not found in the newer commercial varieties. As these older varieties and their corresponding cultures become extinct, this genetic information could be lost forever. The increasing popularity of Cannabis and the requirements of agricultural technology will call for uniform hybrid races that are likely to displace primitive populations worldwide.
Limitation of genetic diversity is certain to result from concerted inbreeding for uniformity. Should inbred Cannabis be attacked by some previously unknown pest or disease, this genetic uniformity could prove disastrous due to potentially resistant diverse genotypes having been dropped from the population. If this genetic complement of resistance cannot be reclaimed from primitive parental material, resistance cannot be introduced into the ravaged population. There may also be currently unrecognized favorable traits which could be irretrievably dropped from the Cannabis gene pool. Human intervention can create new phenotypes by selecting and recombining existing genetic variety, but only nature can create variety in the gene pool itself, through the slow process of random mutation.
This does not mean that importation of seed and selective hybridization are always detrimental. Indeed these principles are often the key to crop improvement, but only when applied knowledgeably and cautiously. The rapid search for improvements must not jeopardize the pool of original genetic information on which adaptation relies. At this time, the future of Cannabis lies in government and clandestine collections. These collections are often inadequate, poorly selected and badly maintained. Indeed, the United Nations Cannabis collection used as the primary seed stock for worldwide governmental research is depleted and spoiled.
The task outlined above is not an easy one, given the current legal restrictions on the collection of Cannabis seed. In spite of this, the conscientious cultivator is making a contribution toward preserving and improving the genetics of this interesting plant.
Even if a grower has no desire to attempt crop improvement, successful strains have to be protected so they do not degenerate and can be reproduced if lost. Left to the selective pressures of an introduced environment, most drug strains will degenerate and lose potency as they acclimatize to the new conditions. Let me cite an example of a typical grower with good intentions.
A grower in northern latitudes selected an ideal spot to grow a crop and prepared the soil well. Seeds were selected from the best floral clusters of several strains available over the past few years, both imported and domestic. Nearly all of the staminate plants were removed as they matured. A nearly seedless crop of beautiful plants resulted. After careful consideration, the few seeds from accidental pollination of the best flowers were kept for the following season. These seeds produced even bigger and better plants than the year before and seed collection was performed as before. The third season, most of the plants were not as large or desirable as the second season, but there were many good individuals. Seed collection and cultivation the fourth season resulted in plants inferior even to the first crop, and this trend continued year after year. What went wrong? The grower collected seed from the best plants each year and grew them under the same conditions. The crop improved the first year. Why did the strain degenerate?
This example illustrates the unconscious selection for undesirable traits. The hypothetical cultivator began well by selecting the best seeds available and growing them properly. The seeds selected for the second season resulted from random hybrid pollinations by early-flowering or overlooked staminate plants and by hermaphrodite pistil late plants. Many of these random pollen-parents may be undesirable for breeding since they may pass on tendencies toward premature maturation, retarded maturation, or hermaphrodism. However, the collected hybrid seeds produce, on the average, larger and more desirable offspring than the first season. This condition is called hybrid vigor and results from the hybrid crossing of two diverse gene pools. The tendency is for many of the dominant characteristics from both parents to be transmitted to the F1 off spring, resulting in particularly large and vigorous plants. This increased vigor due to recombination of dominant genes often raises the cannabinoid level of the F1 offspring. Hybridization also opens up the possibility that undesirable (usually recessive) genes may form pairs and express their characteristics in the F2 offspring. Hybrid vigor may also mask inferior qualities due to abnormally rapid growth. During the second season, random pollinations again accounted for a few seeds and these were collected. This selection draws on a huge gene pool and the possible F2 combinations are tremendous. By the third season the gene pool is tending toward early-maturing plants that are acclimatized to their new conditions instead of the drug-producing conditions of their native environment. These acclimatized members of the third crop have a higher chance of maturing viable seeds than the parental types, and random pollinations will again increase the numbers of acclimatized individuals, and thereby increase the chance that undesirable characteristics associated with acclimatization are transmitted to the next F2 generation. This effect is compounded from generation to generation and finally results in a fully acclimatized weed strain with little drug value.
With some care the breeder can avoid these hidden dangers of unconscious selection. Definite goals are vital to progress in breeding Cannabis. What qualities are desired in a strain that it does not already exhibit? What characteristics does a strain exhibit that are unfavorable and should be bred out? Answers to these questions suggest goals for breeding. In addition to a basic knowledge of Cannabis botany, propagation, and genetics, the successful breeder also becomes aware of the most minute differences and similarities in phenotype. A sensitive rapport is established between breeder and plants and at the same time strict guidelines are followed. A simplified explanation of the time-tested principles of plant breeding shows how this works in practice.
Selection is the first and most important step in the breeding of any plant. The work of the great breeder and plant wizard Luther Burbank stands as a beacon to breeders of exotic strains. His success in improving hundreds of flower, fruit, and vegetable crops was the result of his meticulous selection of parents from hundreds of thousands of seedlings and adults from the world over.
Bear in mind that in the production of any new plant, selection plays the all-important part. First, one must get clearly in mind the kind of plant he wants, then breed and select to that end, always choosing through a series of years the plants which are approaching nearest the ideal, and rejecting all others.
The most important part of Burbank’s message on selection tells breeders to choose the plants “which are approaching nearest the ideal,” and REJECT ALL OTHERS! Random pollinations do not allow the control needed to reject the undesirable parents. Any staminate plant that survives detection and roguing (removal from the population), or any stray staminate branch on a pistillate her maphrodite may become a pollen parent for the next generation. Pollination must be controlled so that only the pollen- and seed-parents that have been carefully selected for favorable traits will give rise to the next generation.
Selection is greatly improved if one has a large sample to choose from! The best plant picked from a group of ten has far less chance of being significantly different from its fellow seedlings than the best plant selected from a sample of (100,000). Burbank often made his initial selections of parents from samples of up to (500,000) seedlings. Difficulties arise for many breeders because they lack the space to keep enough examples of each strain to allow a significant selection. A Cannabis breeder’s goals are restricted by the amount of space available. Formulating a well defined goal lowers the number of individuals needed to perform effective crosses. Another technique used by breeders since the time of Burbank is to make early selections. Seedling plants take up much less space than adults. Thousands of seeds can be germinated in a flat. A flat takes up the same space as a hundred 10-centimeter (4-inch) sprouts or sixteen 30-centimeter (12-inch) seedlings or one 60-centimeter (24-inch) juvenile. An adult plant can easily take up as much space as a hundred flats. Simple arithmetic shows that as many as (10,000) sprouts can be screened in the space required by each mature plant, provided enough seeds are available. Seeds of rare strains are quite valuable and exotic; however, careful selection applied to thousands of individuals, even of such common strains as those from Colombia or Mexico, may produce better offspring than plants from a rare strain where there is little or no opportunity for selection after germination. This does not mean that rare strains are not valuable, but careful selection is even more important to successful breeding. The random pollinations that produce the seeds in most imported marijuana assure a hybrid condition which results in great seedling diversity. Distinctive plants are not hard to discover if the seedling sample is large enough.
Traits considered desirable when breeding Cannabis often involve the yield and quality of the final product, but these characteristics can only be accurately measured after the plant has been harvested and long after it is possible to select or breed it. Early seedling selection, therefore, only works for the most basic traits. These are selected first, and later selections focus on the most desirable characteristics exhibited by juvenile or adult plants. Early traits often give clues to mature phenotypic expression, and criteria for effective early seedling selection are easy to establish. As an example, particularly tall and thin seedlings might prove to be good parents for pulp or fiber production, while seed lings of short internode length and compound branching may be more suitable for flower production. However, many important traits to be selected for in Cannabis floral clusters cannot be judged until long after the parents are gone, so many crosses are made early and selection of seeds made at a later date.
Hybridization is the process of mixing differing gene pools to produce offspring of great genetic variation from which distinctive individuals can be selected. The wind performs random hybridization in nature. Under cultivation, breeders take over to produce specific, controlled hybrids. This process is also known as cross-pollination, cross-fertilization, or simply crossing. If seeds result, they will produce hybrid offspring exhibiting some characteristics from each parent.
Large amounts of hybrid seed are most easily produced by planting two strains side by side, removing the staininate plants of the seed strain, and allowing nature to take its course. Pollen- or seed-sterile strains could be developed for the production of large amounts of hybrid seed without the labor of thinning; however, genes for sterility are rare. It is important to remember that parental weaknesses are transmitted to offspring as well as strengths. Because of this, the most vigorous, healthy plants are always used for hybrid crosses.
Sports (plants or parts of plants carrying and expressing spontaneous mutations) most easily transmit mutant genes to the offspring if they are used as pollen parents. If the parents represent diverse gene pools, hybrid vigor results, because dominant genes tend to carry valuable traits and the differing dominant genes inherited from each parent mask recessive traits inherited from the other. This gives rise to particularly large, healthy individuals. To increase hybrid vigor in offspring, parents of different geographic origins are selected since they will probably represent more diverse gene pools.
Occasionally hybrid offspring will prove inferior to both parents, but the first generation may still contain recessive genes for a favorable characteristic seen in a parent if the parent was homozygous for that trait. First generation (F1) hybrids are therefore inbred to allow recessive genes to recombine and express the desired parental trait. Many breeders stop with the first cross and never realize the genetic potential of their strain. They fail to produce an F2 generation by crossing or self-pollinating F1 offspring. Since most domestic Cannabis strains are F1 hybrids for many characteristics, great diversity and recessive recombination can result from inbreeding domestic hybrid strains. In this way the breeding of the F1 hybrids have already been accomplished, and a year is saved by going directly to F2 hybrids. These F2 hybrids are more likely to express recessive parental traits. From the F2 hybrid generation selections can be made for parents which are used to start new true-breeding strains. Indeed, F2 hybrids might appear with more extreme characteristics than either of the P~ parents. (For example, P1 high-THC X P1 low-THC yields F1 hybrids of intermediate THC content. Selfing the F1 yields F2 hybrids, of both P1 [high and low THC] phenotypes, intermediate F1 phenotypes, and extra-high THC as well as extra-low THC phenotypes.)
Also, as a result of gene recombination, F1 hybrids are not true-breeding and must be reproduced from the original parental strains. When breeders create hybrids they try to produce enough seeds to last for several successive years of cultivation. After initial field tests, undesirable hybrid seeds are destroyed and desirable hybrid seeds stored for later use. If hybrids are to be reproduced, a clone is saved from each parental plant to preserve original parental genes.
Back-crossing is another technique used to produce offspring with reinforced parental characteristics. In this case, a cross is made between one of the F1 or subsequent offspring and either of the parents expressing the desired trait. Once again this provides a chance for recombination and possible expression of the selected parental trait. Back-crossing is a valuable way of producing new strains, but it is often difficult because Cannabis is an annual, so special care is taken to save parental stock for back-crossing the following year. Indoor lighting or greenhouses can be used to protect breeding stock from winter weather. In tropical areas plants may live outside all year. In addition to saving particular parents, a successful breeder always saves many seeds from the original P1 group that produced the valuable characteristic so that other P1 plants also exhibiting the characteristic can be grown and selected for back-crossing at a later time.
Several types of breeding are summarized as follows:
1 – Crossing two varieties having outstanding qualities (hybridization).
2 – Crossing individuals from the F1 generation or selfing F1 individuals to realize the possibilities of the original cross (differentiation).
3 – Back crossing to establish original parental types.
4 – Crossing two similar true-breeding (homozygous) varieties to preserve a mutual trait and restore vigor.
It should be noted that a hybrid plant is not usually hybrid for all characteristics nor does a true-breeding strain breed true for all characteristics. When discussing crosses, we are talking about the inheritance of one or a few traits only. The strain may be true-breeding for only a few traits, hybrid for the rest. Monohybrid crosses involve one trait, dihybrid crosses involve two traits, and so forth. Plants have certain limits of growth, and breeding can only produce a plant that is an expression of some gene already present in the total gene pool. Nothing is actually created by breeding; it is merely the recombination of existing genes into new genotypes. The possibilities of recombination are nearly limitless.
The most common use of hybridization is to cross two outstanding varieties. Hybrids can be produced by crossing selected individuals from different high-potency strains of different origins, such as Thailand and Mexico. These two parents may share only the characteristic of high psycho activity and differ in nearly every other respect. From this great exchange of genes many phenotypes may appear in the F2 generation. From these offspring the breeder selects individuals that express the best characteristics of the parents. As an example, consider some of the offspring from the P1 (parental) cross: Mexico x Thailand. In this case, genes for high drug content are selected from both parents while other desirable characteristics can be selected from either one. Genes for large stature and early maturation are selected from the Mexican seed-parent, and genes for large calyx size and sweet floral aroma are selected from the Thai pollen parent. Many of the F1 offspring exhibit several of the desired characteristics. To further promote gene segregation, the plants most nearly approaching the ideal are crossed among themselves. The F2 generation is a great source of variation and recessive expression. In the F2 generation there are several individuals out of many that exhibit all five of the selected characteristics. Now the process of inbreeding begins, using the desirable F2 parents.
If possible, two or more separate lines are started, never allowing them to interbreed. In this case one acceptable staminate plant is selected along with two pistillate plants (or vice versa). Crosses between the pollen parent and the two seed parents result in two lines of inheritance with slightly differing genetics, but each expressing the desired characteristics. Each generation will produce new, more acceptable combinations.
If two inbred strains are crossed, F1 hybrids will be less variable than if two hybrid strains are crossed. This comes from limiting the diversity of the gene pools in the two strains to be hybridized through previous inbreeding. Further independent selection and inbreeding of the best plants for several generations will establish two strains which are true-breeding for all the originally selected traits. This means that all the offspring from any parents in the strain will give rise to seedlings which all exhibit the selected traits. Successive inbreeding will have resulted in the steady decline in the vigor of the strain.
When lack of vigor interferes with selecting phenotypes for size and hardiness, the two separately selected strains can then be interbred to recombine nonselected genes and restore vigor. This will probably not interfere with breeding for the selected traits unless two different gene systems control the same trait in the two separate lines, and this is highly unlikely. Now the breeder has produced a hybrid strain that breeds true for large size, early maturation, large sweet-smelling calyxes, and high THC level. The goal has been reached!
Wind pollination and dioecious sexuality favor a heterozygous gene pool in Cannabis. Through Anbreeding, hybrids are adapted from a heterozygous gene pool to a homozygous gene pool, providing the genetic stability needed to create true-breeding strains. Establishing pure strains enables the breeder to make hybrid crosses with a better chance of predicting the outcome. Hybrids can be created that are not reproducible in the F2 generation. Commercial strains of seeds could be developed that would have to be purchased each year, because the F1 hybrids of two pure-bred lines do not breed true. Thus, a seed breeder can protect the investment in the results of breeding, since it would be nearly impossible to reproduce the parents from F2 seeds.
At this time it seems unlikely that a plant patent would be awarded for a pure-breeding strain of drug Cannabis. Note: plant patents already exist in the U. S. In the future, however, with the legalization of cultivation, it is a certainty that corporations with the time, space, and money to produce pure and hybrid strains of Cannabis will apply for patents. It may be legal to grow only certain patented strains produced by large seed companies. Will this be how government and industry combine to control the quality and quantity and cost of “drug” Cannabis?
Much of the breeding effort of North American cultivators is concerned with acclimatizing high-THC strains of equatorial origin to the climate of their growing area while preserving potency. Late-maturing, slow, and irregularly flowering strains like those of Thailand have difficulty maturing in many parts of North America. Even in a green house, it may not be possible to mature plants to their full native potential.
To develop an early maturing and rapid flowering strain, a breeder may hybridize as in the previous example. However, if it is important to preserve unique imported genetics, hybridizing may be inadvisable. Alternatively, a pure cross is made between two or more Thai plants that most closely approach the ideal in blooming early. At this point the breeder may ignore many other traits and aim at breeding an earlier-maturing variety of a pure Thai strain. This strain may still mature considerably later than is ideal for the particular location unless selective pressure is exerted. If further crosses are made with several individuals that satisfy other criteria such as high THC content, these may be used to develop another pure Thai strain of high THC content. After these true-breeding lines have been established, a dihybrid pure cross can be made in an attempt to produce an F1 generation containing early maturing, high THC strains of pure Thai genetics, in other words, an acclimatized drug strain.
Crosses made without a clear goal in mind lead to strains that acclimatize while losing many favorable characteristics. A successful breeder is careful not to overlook a characteristic that may prove useful. It is imperative that original imported Cannabis genetics be preserved intact to protect the species from loss of genetic variety through excessive hybridization. A currently unrecognized gene may be responsible for controlling resistance to a pest or disease, and it may only be possible to breed for this gene by back-crossing existing strains to original parental gene pools.
Once pure breeding lines have been established, plant breeders classify and statistically analyze the offspring to determine the patterns of inheritance for that trait. This is the system used by Gregor Mendel to formulate the basic laws of inheritance and aid the modern breeder in predicting the outcome of crosses.
1 – Two pure lines of Cannabis that differ in a particular trait are located.
2 – These two pure-breeding lines are crossed to produce an F1 generation.
3 – The F1 generation is inbred.
4 – The offspring of the F1 and F2 generations are classified with regard to the trait being studied.
5 – The results are analyzed statistically.
6 – The results are compared to known patterns of inheritance so the nature of the genes being selected for can be characterized.
1 – The genotypes of plants are controlled by genes which are passed on unchanged from generation to generation.
2 – Genes occur in pairs, one from the gamete of the staminate parent (male) and one from the gamete of the pistillate (female) parent.
3 – When the members of a gene pair differ in their effect upon phenotype, the plant is termed hybrid or heterozygous.
4 – When the members of a pair of genes are equal in their effect upon phenotype, then they are termed true-breeding or homozygous.
5 – Pairs of genes controlling different phenotypic traits are (usually) inherited independently.
6 – Dominance relations and gene interaction can alter the phenotypic ratios of the F1, F2, and subsequent generations.
1. General Traits
2. Seedling Traits
3. Leaf Traits
4. Fiber Traits
5. Floral Traits
2. Medical cannabis
3. Legality of cannabis
4. Legality of cannabis by country
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