OMG ...........please dont get the Cactus man going on world issues. I will end up banned for political rablerousing. .........
Nuff said.
Stopped in to share a little gem with all but I know at
@Tnelz especially will appreciate this. Enjoy...........
Pollen and Plant Improvement (Strain Improvement)
http://medicalinvalid.com/experts/expert/title.cfm?artID=683
)Posted the link as the actual article would take up too much space.
Hey
Sorry about the invalid link
@Tnelz So I didnt want to clog up the thread but looks like I have to so you guyz can access the article I originally tried to post the link to. Hear you go.
Plants that are pollinated by wind produce more pollen than plants that are pollinated by insects. They need an abundance of pollen because the wind takes a cloud of pollen from male flowers and only a small amount of it lands on female flowers. Insect pollinated plants do not need as much pollen because bees transfer it directly from one flower to the next. Marijuana is wind pollinated.
Pollen consists of two cells: one that grows into the pollen tube, and one meant to fertilize the egg.
Cannabis is one of a few species of plants that has male and female individuals. Holly and some kinds of cucumbers are other examples. Cannabis’ relative, “hops” has the same pattern. Like corn, the plant uses the wind to carry pollen to the female flowers, which are small and do not have petals. One could simply remove the pollen bearing flowers as they ripen or employ the technique used with corn. An ordinary paper bag placed over the male flowers and pollen collects inside. Unless breeding the plant, the goal is not to allow pollination to occur. This increases resin production in the female plant. A single cannabis plant is capable of producing several thousand seeds. Avoid pollinating the extreme lower branches, as they will likely not mature into viable seeds. Four to five weeks later, you should have a bunch of viable seeds to grow or share.
Producing Seeds
Eventually, every grower is going to want to produce marijuana seeds. Developing a new stable strain is beyond the scope of this discussion and requires the ability to grow hundreds or even thousands of breeding plants. However, just about any grower can manage to preserve some genetics by growing (f2) seeds where they have crossed a male and female of the same strain, or can produce a simple cross which would be referred to as (strain 1 x strain 2).
Selecting Suitable Parents
There are a number of important characteristics when selecting parents female. Select a male with characteristics you want. Obviously, potency, yield, and psychoactive effects are critical to the selection process. However, some other important traits are size, odor, taste, resistance to mold and contaminants, early finishing and consistency.
Collecting and Storing Pollen
In order to collect pollen you simply put down newspaper around the base of the plant. The pollen will fall from the plant onto the newspaper. You can then put this newspaper into a plastic bag and store it in the refrigerator or you can freeze it. Pollen will keep for a few months in the refrigerator. The freezer will extend that to up to six months but gives the pollen a lower chance of viability that increases with time.
Pollinating a Plant
To pollinate a plant you can brush the pollen on a flower with a (cotton swab or small brush) or you can take the (plastic bag or paper bag), wrap the flower inside it, and shake. You can selectively pollinate plants or even individual buds.
Sexual versus Asexual Propagation
Cannabis 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, layering, 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.
If two clones from a pistillate cannabis plant are placed in differing environments, their genotypes will remain identical. However, the clone grown in the shade will grow tall and slender and mature late, while the clone grown in full sun will remain short and bushy and mature much earlier.
Sexual Propagation
Sexual propagation requires the union of staminate pollen and pistillate ovule, the formation of viable seed, and the creation of individuals with newly recombinant genotypes. Pollen and ovules are formed by reduction divisions (meiosis) in which the 10 chromosome pairs fail to replicate, so that each of the two daughter cells contains one-half of the chromosomes from the mother cell. This is known as the haploid (in) condition where (in) = 10 chromosomes. The diploid condition is restored upon fertilization resulting in diploid (2n) individuals with a haploid set of chromosomes from each parent. Offspring may resemble the staminate, pistillate, both, or neither parent and considerable variation in offspring is to be expected. A single gene or a combination of genes, resulting in further potential diversity, may control traits.
The terms homozygous and heterozygous are useful in describing the genotype of a particular plant. If the genes controlling a trait are the same on one chromosome as those on the opposite member of the chromosome pair (homologous chromosomes), the plant is homozygous and will "breed true" for that trait if self-pollinated or crossed with an individual of identical genotype for that trait. The traits possessed by the homozygous parent will be transmitted to the offspring, which will resemble each other and the parent. If the genes on one chromosome differ from the genes on its homologous chromosome then the plant is termed heterozygous; the resultant offspring may not possess the parental traits and will most probably differ from each other. Imported Cannabis strains usually exhibit great seedling diversity for most traits and many types will be discovered.
To minimize variation in seedlings and ensure preservation of desirable parental traits in offspring, certain careful procedures are followed.
The Life Cycle and Sinsemilla (seedless) Cultivation
A wild cannabis plant grows from seed to a seedling, to a prefloral juvenile, to either pollen or seed bearing adult, following the usual pattern of development and sexual reproduction. Fiber and drug production both interfere with the natural cycle and block the pathways of inheritance. Fiber crops are usually harvested in the juvenile or prefloral stage, before viable seed is produced, while (sinsemilla) or seedless marijuana cultivation eliminates pollination and subsequent seed production. In the case of cultivated cannabis crops, special techniques are used to produce viable seed for the following year without jeopardizing the quality of the final product.
Modern fiber or hemp farmer’s use commercially produced high fiber content strains of even maturation. Monoecious strains are often used because they mature more evenly than dioecious strains. The hemp breeder sets up test plots where phenotypes can be recorded and controlled crosses can be made. A farmer may leave a portion of his crop to develop mature seeds that he collects for the following year. If a hybrid variety is grown, the offspring will not all resemble the parent crop and desirable characteristics may be lost.
Growers of seeded marijuana for smoking or hashish production collect vast quantities of seeds that fall from the flowers during harvesting, drying, and processing. A mature pistillate plant can produce tens of thousands of seeds if freely pollinated. Seedless marijuana is grown by removing all the staminate(male) plants from a patch, eliminating every pollen source, and allowing the pistillate plants to produce massive clusters of unfertilized flowers.
Various theories have arisen to explain the unusually potent psychoactive properties of unfertilized cannabis. In general, these theories have as their central theme the extraordinarily long, frustrated struggle of the pistillate plant to reproduce, and many theories are both twisted and romantic. What actually happens when a pistillate plant remains unfertilized for its entire life and how this ultimately affects the cannabinoid (class of molecules found only in Cannabis) and terpene (a class of aromatic organic compounds) levels remains a mystery. It is assumed, however, that seeding cuts the life of the plant short and THC (tetrahydrocannabinol the major psychoactive compound in cannabis) does not have enough time to accumulate. Hormonal changes associated with seeding definitely affect all metabolic processes within the plant including cannabinoid biosynthesis. The exact nature of these changes is unknown but probably involves imbalance in the enzymatic systems controlling cannabinoid production. Upon fertilization, the plant’s energies are channeled into seed production instead of increased resin production. Sinsemilla plants continue to produce new floral clusters until late fail, while seeded plants cease floral production. It is also suspected that capitate-stalked trichome production might cease when the calyx is fertilized. If this is the case, then sinsemilla may be higher in THC because of uninterrupted floral growth, trichome formation and cannabinoid production. What is important with respect to propagation is that once again, the farmer has interfered with the life cycle and no naturally fertilized seeds have been produced.
The careful propagator, however, can produce as many seeds of pure types as needed for future research without risk of pollinating the precious crop. Staminate parents exhibiting favorable characteristics are reproductively isolated while pollen is carefully collected and applied to only select flowers of the pistillate parents.
Many cultivators overlook the staminate plant, considering it useless if not detrimental. Nevertheless, the staminate plant contributes half of the genotype expressed in the offspring. Not only are staminate plants preserved for breeding, but also they must be allowed to mature, uninhibited, until their phenotypes can be determined and the most favorable individuals selected. Pollen may also be stored for short periods for later breeding.
Biology of Pollination
Pollination is the event of pollen landing on a stigmatic surface such as the pistil, and fertilization is the union of the staminate chromosomes from the pollen with the pistillate chromosomes from the ovule.
Pollination begins with dehiscence (release of pollen) from staminate flowers. Millions of pollen grains float through the air on light breezes, and many land on the stigmatic surfaces of nearby pistillate plants. If the pistil is ripe, the pollen grain will germinate and send out a long pollen tube much as a seed pushes out a root. The tube contains a haploid (in) generative nucleus and grows downward toward the ovule at the base of the pistils. When the pollen tube reaches the ovule, the staminate haploid nucleus fuses with the pistillate haploid nucleus and the diploid condition is restored. Germination of the pollen grain occurs 15 to 20 minutes after contact with the stigmatic surface (pistil); fertilization may take up to two days in cooler temperatures. Soon after fertilization, the pistils wither away as the ovule and surrounding calyx begin to swell. If the plant is properly watered, seed will form and sexual reproduction is complete. It is crucial that no part of the cycle be interrupted or viable seed will not form. If the pollen is subjected to extremes of temperature, humidity, or moisture, it will fail to germinate, the pollen tube will die prior to fertilization, or the embryo will be unable to develop into a mature seed. Techniques for successful pollination have been designed with all these criteria in mind.
Controlled versus Random Pollinations
The seeds with which most cultivators begin represent varied genotypes even when they originate from the same floral cluster of marijuana, and not all of these genotypes will prove favorable. Seeds collected from imported shipments are the result of very random pollinations among many genotypes. If elimination of pollination was attempted and only a few seeds appear, the likelihood is very high that a late flowering staminate plant or a hermaphrodite, adversely affecting the genotype of the offspring, caused these pollinations. Once the offspring of imported strains are in the hands of a competent breeder, selection and replication of favorable phenotypes by controlled breeding may begin. Only one or two individuals out of many may prove acceptable as parents. If the cultivator allows random pollination to occur again, the population not only fails to improve, it may even degenerate through natural and accidental selection of unfavorable traits. We must therefore turn to techniques of controlled pollination by which the breeder attempts to take control and determine the genotype of future offspring.
Data Collection
Keeping accurate notes and records is a key to successful plant breeding. Crosses among ten pure strains (ten staminate and ten pistillate parents) result in ten pure and ninety hybrid crosses. It is an endless and inefficient task to attempt to remember the significance of each little number and colored tag associated with each cross. The well-organized breeder will free himself from this mental burden and possible confusion by entering vital data about crosses, phenotypes, and growth conditions in a system with one number corresponding to each member of the population.
The single most important task in the proper collection of data is to establish undeniable credibility. Memory fails, and remembering the steps that might possibly have led to the production of a favorable strain does not constitute the data needed to reproduce that strain. Data is always written down; memory is not a reliable record. A record book contains a numbered page for each plant, and each separate cross is tagged on the pistillate parent and recorded as follows: (seed of pistillate parent X pollen or staminate parent). In addition, the date of pollination is included and room is left for the date of seed harvest. Samples of the parental plants are saved as voucher specimens for later characterization and analysis.
Pollination Techniques
Controlled hand pollination consists of two basic steps: collecting pollen from the anthers of the staminate parent and applying pollen to the receptive stigmatic surfaces of the pistillate parent. Both steps are carefully controlled so that no pollen escapes to cause random pollinations. Since Cannabis is a wind-pollinated species, enclosures are employed which isolate the ripe flowers from wind, eliminating pollination, yet allowing enough light penetration and air circulation for the pollen and seeds to develop without suffocating. Paper and very tightly woven cloth seem to be the most suitable materials. Coarse cloth allows pollen to escape and plastic materials tend to collect transpired water and rot the flowers. Light-colored opaque or translucent reflective materials remain cooler in the sun than dark or transparent materials, which either absorb solar heat directly or create a greenhouse effect, heating the flowers inside and killing the pollen. Pollination bags are easily constructed by gluing together vegetable parchment (a strong breathable paper for steaming vegetables) and clear nylon oven bags (for observation windows) with silicon glue. Breathable synthetic fabrics such as Gore-Tex are used with great success. Seed production requires both successful pollination and fertilization, so the conditions inside the enclosures must remain suitable for pollen tube growth and fertilization. It is most convenient and effective to use the same enclosure to collect pollen and apply it, reducing contamination during pollen transfer. Controlled "free" pollinations may also be made if only one pollen parent is allowed to remain in an isolated area of the field and hermaphrodites or late maturing staminate plants cause no pollinations. If the selected staminate parent drops pollen when there are only a few primordial flowers on the pistillate seed parent, then only a few seeds will form in the basal flowers and the rest of the flower cluster will be seedless. Early fertilization might also help fix the sex of the pistillate plant, helping to prevent hermaphrodism. Later, hand pollinations can be performed on the same pistillate parent by removing the early seeds from each limb to be re-pollinated, so avoiding confusion. Hermaphrodite or monoecious plants may be isolated from the remainder of the population and allowed to freely self-pollinate if pure-breeding offspring are desired to preserve a selected trait. Self-fertile hermaphrodites usually give rise to hermaphrodite offspring.
Pollen may be collected in several ways. If the propagator has an isolated area, where staminate plants can grow separate from each other to avoid mutual contamination and can be allowed to shed pollen without endangering the remainder of the population, then direct collection may be used. A small vial, glass plate, or mirror is held beneath a recently opened staminate flower that appears to be releasing pollen, and the pollen is dislodged by tapping the anthers. Placing whole limbs or clusters of staminate flowers may also collect pollen on a piece of paper or glass and allowing them to dry in a cool, still place. Pollen will drop from some of the anthers as they dry, and this may be scraped up and stored for a short time in a cool, dark, dry spot.
Any breeze may interfere with collection and cause contamination with pollen from neighboring plants. Early morning is the best time to collect pollen, as it has not been exposed to the heat of the day. All equipment used for collection, including hands, must be cleaned before continuing to the next pollen source. This ensures protection of each pollen sample from contamination with pollen from different plants.
The first step in collecting pollen is, of course, the selection of a staminate or pollen parent. Healthy individuals with well-developed clusters of flowers are chosen. The appearance of the first staminate primordial or male sex signs often brings a feeling of panic to the cultivator of seedless cannabis, and potential pollen parents are prematurely removed. Staminate primordial need to develop from one to five weeks before the flowers open and pollen is released. During this period, the selected pollen plants are carefully watched, daily or hourly if necessary, for developmental rates vary greatly and pollen may be released quite early in some strains. The remaining staminate plants that are unsuitable for breeding are destroyed and the pollen plants specially labeled to avoid confusion and extra work.
As the first flowers begin to swell, they are removed prior to pollen release and destroyed. Tossing them on the ground is ineffective because they may release pollen as they dry. When the staminate plant enters its full floral condition and more ripe flowers appear than can be easily controlled, limbs with the ripest flowers are chosen. It is usually safest to collect pollen from two limbs for each intended cross, in case one fails to develop. If there are ten prospective seed parents, pollen from twenty limbs on the pollen parent is collected. In this case, the twenty most flowered limb tips are selected and all the remaining flowering clusters on the plant are removed to prevent stray pollinations. Large leaves are left on the remainder of the plant but are removed at the limb tips to minimize condensation of water vapor released inside the enclosure. The portions removed from the pollen parent are saved for later analysis and phenotype characterization.
Now a pistillate plant is chosen as the seed parent. A pistillate flower cluster is ripe for fertilization so long as pale, slender pistils emerge from the calyxes. Withered, dark pistils protruding from swollen, resin encrusted calyxes are a sign that the reproductive peak has long passed. Cannabis plants can be successfully pollinated as soon as the first primordial show pistils and until just before harvest, but the largest yield of uniform, healthy seeds is achieved by pollinating in the peak floral stage. At this time, the seed plant is covered with thick clusters of white pistils. Few pistils are brown and withered, and resin production has just begun. This is the most receptive time for fertilization, still early in the seed plant’s life, with plenty of time remaining for the seeds to mature. Healthy, well-flowered lower limbs on the shaded side of the plant are selected. Shaded buds will not heat up in the bags as much as buds in the hot sun, and this will help protect the sensitive pistils. When possible, two terminal clusters of pistillate flowers are chosen for each pollen bag. In this way, with two pollen bags for each seed parent and two clusters of pistillate flowers for each bag, there are four opportunities to perform the cross successfully. Remember that production of viable seed requires successful pollination, fertilization and embryo development. Since interfering with any part of this cycle precludes seed development, fertilization failure is guarded against by duplicating all steps.
Before the pollen bags are used, the seed parent information is added to the pollen parent data. Included is the number of the seed parent, the date of pollination, and any comments about the phenotypes of both parents. For each of the selected pistillate clusters, a tag containing the same information is made and secured to the limb below the closure of the bag. A warm, windless evening is chosen for pollination so the pollen tube has time to grow before sunrise. After removing most of the shade leaves from the tips of the limbs to be pollinated, the pollen is tapped away from the mouth of the bag. The bag is then carefully opened and slipped over two inverted limb tips, taking care not to release any pollen, and tied securely with an expandable band. The bag is shaken vigorously, so the pollen will be evenly dispersed throughout the bag, facilitating complete pollination.
If only a small quantity of pollen is available, it may be used more sparingly by diluting with a neutral powder such as flour before it is used. When pure pollen is used, many pollen grains may land on each pistil when only one is needed for fertilization. Diluted pollen will go further and still produce high fertilization rates. Diluting one part pollen with ten to one hundred parts flour is common. Powdered fungicides are also used since this helps retard the growth of molds in the maturing, seeded, floral clusters.
The bags may remain on the seed parent for sometime; seeds usually begin to develop within a few days, but their development will be retarded by the bags. The propagator waits three full sunny days, then carefully removes and sterilizes or destroys the bags. This way there is little chance of stray pollination. Any viable pollen that failed to pollinate the seed parent will germinate in the warm moist bag and die within three days, along with many of the unpollinated pistils. In particularly cool or overcast conditions a week may be necessary, but the bag is removed at the earliest safe time to ensure proper seed development without stray pollinations. As soon as the bag is removed, the calyxes begin to swell with seed, indicating successful fertilization. Seed parents then need good irrigation or development will be retarded, resulting in small, immature, and nonviable seeds. Seeds develop fastest in warm weather and take usually from two to four weeks to mature completely. In cold weather, seeds may take up to two months to mature. If seeds get wet in fall rains, they may sprout. Seeds are removed when the calyx begins to dry up and the dark shiny perianth (seed coat) can be seen protruding from the drying calyx. Seeds are labeled and stored in a cool, dark, dry place. This is the method employed by breeders to create seeds of known parentage used to study and improve cannabis genetics.
Seed Selection
Nearly every cultivated cannabis plant, no matter what its future, began as a germinating seed; and nearly all cannabis cultivators, no matter what their intention, start with seeds that are gifts from a fellow cultivator or extracted from imported shipments of marijuana. Very little true control can be exercised in seed selection unless the cultivator travels to select growing plants with favorable characteristics and personally pollinate them. This is not possible for most cultivators or researchers and they usually rely on imported seeds. These seeds are of unknown parentage, the product of natural selection or of breeding by the original farmer. Certain basic problems affect the genetic purity and predictability of collected seed.
1 - If a Cannabis sample is heavily seeded, then the majority of the male plants were allowed to mature and release pollen. Since cannabis is wind-pollinated, many pollen parents (including early and late maturing staminate and hermaphrodite plants) will contribute to the seeds in any batch of pistillate flowers. If the seeds are all taken from one flower cluster with favorable characteristics, then at least the pistillate or seed parent is the same for all those seeds, though the pollen may have come from many different parents. This creates great diversity in offspring.
2 - In very lightly seeded or nearly sinsemilla, cannabis pollination has largely been prevented by the removal of staminate parents prior to the release of pollen. The few seeds that do form often result from pollen from hermaphrodite plants that went undetected by the farmer or by random wind-borne pollen from wild plants or a nearby field. Hermaphrodite parents often produce hermaphrodite offspring and this may not be desirable.
3 - Most domestic cannabis strains are random hybrids. This is the result of limited selection of pollen parents, impure breeding conditions, and lack of adequate space to isolate pollen parents from the remainder of the crop.
When selecting seeds, the propagator will frequently look for seed plants that have been carefully bred locally by another propagator. Even if they are hybrids, there is a better chance of success than with imported seeds, provided certain guidelines are followed:
1 - The dried seeded flower clusters are free of staminate flowers that might have caused hermaphrodite pollinations.
2 - The flowering clusters are tested for desirable traits and seeds selected from the best.
3 - Healthy, robust seeds are selected. Large, dark seeds are best; smaller, paler seeds are avoided since these are usually less mature and less viable.
4 - If accurate information is not available about the pollen parent, then selection proceeds on common sense and luck. Mature seeds with dried calyxes in the basal portions of the floral clusters along the main stems occur in the earliest pistillate flowers to appear and must have been pollinated by early-maturing pollen parents. These seeds have a high chance of producing early-maturing offspring. By contrast, mature seeds selected from the tips of floral clusters, often surrounded by immature seeds, are formed in later-appearing pistillate flowers. Later-maturing staminate or hermaphrodite pollen parents likely pollinated these flowers, and their seeds should mature later and have a greater chance of producing hermaphrodite off spring. The pollen parent also exerts some influence on the appearance of the resulting seed. If seeds are collected from the same part of a flower cluster and selected for similar size, shape, color, and perianth patterns, then it is more likely that the pollinations represent fewer different gene pools and will produce more uniform offspring.
5 - Seeds are collected from strains that best suit the locality; these usually come from similar climates and latitudes.
6 - Pure strain seeds come from crosses between parents of the same origin.
7 - Hybrid seeds come from crosses between pure strain parents of different origins.
8 - Seeds from hybrid plants, or seeds resulting from pollination by hybrid plants, should be avoided, since these will not reliably reproduce the phenotype of either parent.
Seed Stock
Seed stocks are graded by the amount of control exerted by the collector in selecting the parents.
Grade #1 - Seed parent and pollen parent are known and there is absolutely no possibility that the seeds resulted from pollen contamination.
Grade #2 - Seed parent is known but several known staminate or hermaphrodite pollen parents are involved.
Grade #3 - Pistillate parent is known and pollen parents are unknown.
Grade #4 - Neither parent is known, but the seeds are collected from one floral cluster, so the pistillate seed parent age traits may be characterized.
Grade #5 - Parentage is unknown but origin is certain, such as seeds collected from the bottom of a bag of imported Cannabis.
Grade #6 - Parentage and origin are unknown.
When a male is starting to flower (2-4 weeks before the females), it should be removed from the females so it does not pollinate them. It is taken to a separate area. Any place that gets just a few hours of light per day will be adequate, including close to a window in a separate room in the house. Put newspaper or glass under it to catch the pollen as the flowers drop it.
Keep a male alive indefinitely by bending the top severely and putting it in mild shock that delays its maturity. Alternatively, take the tops as they mature and put the branches in water, over a piece of plate glass. Shake the branches every morning to release pollen onto the glass and then scrap it with a razor blade to collect it. A male pruned this way can stay alive indefinitely and will continue to produce flowers if it gets suitable dark periods. This is much better than putting pollen in the freezer! Fresh pollen is always best.
When breeding marijuana save pollen in an airtight bag in the freezer. It will be good for about a month. It may be several more weeks before the females are ready to pollinate. Put a paper towel in the bag with the pollen to absorb moisture. A plant is ready to pollinate two weeks after the clusters of female flowers first appear. If you pollinate too early, it may not work. Wait until the female flowers are well established.
Use a paper bag to pollinate a branch of a female plant. Use different pollen from two males on separate branches. Wrap the bag around the branch and seal it at the opening to the branch. Shake the branch vigorously. Wet the paper bag after a few minutes with a sprayer and then carefully remove it. Large plastic zip-lock bags also. Slip the bag over the male branch and shake the pollen loose. Carefully remove the bad and zip it up. It should be very dusty with pollen. To pollinate, place it over a single branch of the female, zipping it up sideways around the stem so no pollen leaks out. Shake the bag and the stem at the same time. Allow to settle for an hour or two and shake it again. Remove it a few hours later. Your branch is now well pollinated and should show signs of visible seed production in two weeks, with ripe seeds splitting the calyxes by three to six weeks. One pollinated branch can create hundreds of seeds, so it should not be necessary to pollinate more than one or two branches in most cases.
When crossing two different varieties, a third variety of plant is created. If you know what characteristics you are looking for in a new strain, you will need several plants to choose from in order to have the best chance of finding all the qualities desired. Sometimes, if the two plants bred had dominant genes characteristics, it will be impossible to get the plant you want from one single cross. It is necessary to interbreed two plants from the same batch of resultant seeds from the initial cross. Recessive genes will become available, and the plant characteristics you desire may only be possible in this manner.
You may want to breed two very different strains together. This gives what we refer to as "hybrid vigor". In other words, often the best strains are created by taking two very different strains and mating them. Less robust plants may be the result of interbreeding. Because it opens up recessive gene traits that may lead to reduced potency.
Hybrid offspring will all be very different from each other. Plants grown from the same batch of seeds collected from the same plant can be very different. It is then necessary to try each plant separately and decide on its individual merits. If you find one that seems to be far above the rest in terms of early flowering, high yield, etc., then these plants are the ones you want to breed.
Your goal is always to improve the strains you produce.
Seeds take 4 weeks minimum to form and mature to viability.
Pollen only needs to be applied once to initiate seed formation but obviously repeated applications will produce more seeds although it should
not be done with less than five weeks to full maturity or you end up having immature seeds (need extra time on the plant) so if it is a selective pollination (only part of the plant is pollinated).
Breeding
All of the marijuana 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 marijuana. 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 marijuana, 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 marijuana have been lost.
Changes in agricultural techniques brought on by technological pressure, greed, and full-scale eradication programs have altered the selective pressures influencing marijuana genetics. Large shipments of inferior marijuana 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 marijuana, 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 marijuana 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 some previously unknown pest or disease attack inbred marijuana, 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 that could be irretrievably dropped from the marijuana 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 marijuana lies in government and clandestine collections. These collections are often inadequate, poorly selected and badly maintained. Indeed, the United Nations marijuana collection used as the primary seed stock for worldwide governmental research is depleted and spoiled.
Several steps must be taken to preserve our vanishing genetic resources, and action must be immediate:
• Seeds and pollen should be collected directly from reliable and knowledgeable sources. Government seizures and smuggled shipments are seldom reliable seed sources. The characteristics of both parents must be known; consequently, mixed bales of randomly pollinated marijuana are not suitable seed sources, even if the exact origin of the sample is certain. Direct contact should be made with the farmer-breeder responsible for carrying on the breeding traditions that have produced the sample. Accurate records of every possible parameter of growth must be kept with carefully stored triplicate sets of seeds.
• Since Marijuana seeds do not remain viable forever, even under the best storage conditions, seed samples should be replenished every third year. Collections should be planted in conditions as similar as possible to their original niche and allowed to reproduce freely to minimize natural and artificial selection of genes and ensure the preservation of the entire gene pool. Half of the original seed collection should be retained until the viability of further generations is confirmed, and to provide parental material for comparison and backcrossing. Phenotypic data about these subsequent generations should be carefully recorded to aid in understanding the genotypes contained in the collection. Favorable traits of each strain should be
characterized and cataloged.
• It is possible that in the future, marijuana cultivation for resale, or even personal use, will be legal but only for approved, patented strains. Special caution would be needed to preserve variety in the gene pool should the patenting of marijuana strains become a reality. (already happening)
• Favorable traits must be carefully integrated into existing strains.
The task outlined above is not an easy one, given the current legal restrictions on the collection of marijuana seed. In spite of this, the conscientious cultivator is contributing 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 and 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 improved plants than the year before and seed collection was performed as before. The third seasons, 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, but 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 will be transmitted to the next F2 generation. This effect is compounded from generation to generation and finally results in a fully acclimatized weed strain of little drug value.
With some care, the breeder can avoid these hidden dangers of unconscious selection. Definite goals are vital to progress in breeding marijuana. What qualities are desired in a strain that it does not already exhibit? What characteristics do 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 marijuana 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 that are approaching nearest the ideal, and rejecting all others.
Luther Burbank:
Proper selection of prospective parents is only possible if the breeder is familiar with the variable characteristics of marijuana that may be genetically controlled, has a way to accurately measure these variations, and has established goals for improving these characteristics by selective breeding. A detailed list of variable traits of marijuana, including parameters of variation for each trait and comments pertaining to selective breeding for or against it. By selecting against unfavorable traits while selecting for favorable ones, the unconscious breeding of poor strains is avoided.
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 hermaphrodite 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 from the best plant selected from a sample of one hundred thousand. Burbank often made his initial selections of parents from samples of up to five hundred thousand seedlings. Difficulties arise for many breeders because they lack the space to keep enough examples of each strain to allow a significant selection. A marijuana 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 do. Thousands of seeds can be germinated in a flat. A flat takes up the same space as a hundred 10-centimeter (4-inch) sprouts, 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 ten thousand 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 that result in great seedling diversity. Distinctive plants are not hard to discover if the seedling sample is large enough.
Traits considered desirable when breeding marijuana often involves 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 seedlings of short internode length and compound branching may be more suitable for flower production. However, many important traits to be selected for in marijuana floral clusters cannot be judged until long after the parents are gone, so many crosses are made early and selection of seeds made later.
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 gene pools that are more diverse.
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 marijuana 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 has 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 that are used to start new true-breeding strains. Indeed, F2 hybrids might appear with more extreme characteristics than either of the (P) parents has. (For example, P1 high-THC X P1 low-THC yields F1 hybrids of intermediate THC content. Self-fertilizing 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.
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Because 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.
Backcrossing is another technique used to produce offspring with reinforced parental characteristics. In this case, a cross is made between one of the (F) 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 marijuana is an annual, so special care is taken to save parental stock for backcrossing 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 backcrossing later.
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 (self fertilizing) 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 are 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, several individuals out of many 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 example, one acceptable staminate (male) plant is selected along with two pistillate (female) 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 that 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 that all exhibit the selected traits.
Successive inbreeding (by this time) has resulted in a 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 unselected 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 marijuana. Through inbreeding, 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 purebred 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 marijuana. In the very near 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 marijuana (like Monsanto) will apply for patents. It may be legal to grow only certain patented strains produced by large seed companies. This is how the government and industry will gain control of medical marijuana.
Acclimatization
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 is hard to get Thai to reach its full maturation and potential in a season.
To develop an early maturing and rapidly 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 (like high CBD levels), these may be used to develop another pure Thai strain with high CBD 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 CBD content 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 marijuana 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 backcrossing 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 marijuana 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 studied.
Fixing Traits
Fixing traits (producing homozygous offspring) in marijuana strains is more difficult than it is in many other flowering plants. With monoecious strains or hermaphrodites, it is possible to fix traits by self-pollinating individual exhibiting favorable traits. In this case, one plant acts as both mother and father. However, most strains of marijuana are dioecious, and unless hermaphroditic reactions can be induced, another parent exhibiting the trait is required to fix the trait. If this is not possible, the unique individual may be crossed with a plant not exhibiting the trait, inbred in the F1 generation, and selections of parents exhibiting the favorable trait made from the F2 generation (this is very difficult).
If a trait is needed for development of a dioecious strain, it might first be discovered in a monoecious strain and then fixed through self-fertilization and selecting homozygous offspring. Dioecious individuals can then be selected from the monoecious population and these individuals crossed to breed out monoecism in subsequent generations.
Galoch (1978) indicated that gibberellic acid (GA3) promoted stamen production while indoleacetic acid (IAA), ethrel, and kinetin promoted pistil production in prefloral dioecious marijuana. Sex alteration has several useful applications. Most importantly, if only one parent expressing a desirable trait is found, it is difficult to perform a cross unless it happens to be a hermaphrodite plant. Plant hormones are used to change the sex of a cutting from the desirable plant, and this cutting used to mate with it. This is most easily accomplished by changing a pistillate(female) cutting to a staminate (pollen) parent, using a spray of 100-ppm gibberellic acid in water each day for five consecutive days. Within two weeks staminate flowers may appear. Pollen can then be collected for self-fertilizing with the original pistillate parent. Offspring from the cross should also be mostly pistillate since the breeder is self-fertilizing for pistillate sexuality. Staminate parents reversed to pistillate floral production make inferior seed-parents since few pistillate flowers and seeds are formed.
If entire crops could be manipulated early in life to produce all pistillate or staminate plants, seed production and seedless medical marijuana production would be greatly facilitated.
Sex reversal for breeding can also be accomplished by mutilation and by photoperiod alteration. A well-rooted, flourishing cutting from the parent plant is pruned back to 25% of its original size and stripped of all its remaining flowers. New growth will appear within a few days, and several flowers of reversed sexual type often appear. Flowers of the unwanted sex are removed until the cutting is needed for fertilization. Extremely short light cycles (6-8 hour photoperiod) can also cause sex reversal. However, this process takes longer and is much more difficult to perform in the field.
Genotype and Phenotype Ratios
Remember, in attempting to fix favorable characteristics, a monohybrid cross gives rise to four possible recombinant genotypes, a dihybrid cross gives rise to 16 possible recombinant genotypes, and so forth.
Phenotype and genotype ratios are probabilistic. If recessive genes are desired for three traits, it is not effective to raise only 64 offspring and count on getting one homozygous recessive individual. To increase the probability of success it is better to raise hundreds of offspring, choosing only the best homozygous recessive individuals as future parents. All laws of inheritance are based on chance and offspring may not approach predicted ratios until many more have been phenotypically characterized and grouped than the theoretical minimums.
A mosaic of thousands of subtle overlapping traits expresses the genotype of each individual. It is the sum total of these traits that determines the general phenotype of an individual. It is often difficult to determine if the characteristic being selected is one trait or the blending of several traits and whether one or several pairs of genes control these traits. It often makes little difference that a breeder does not have plants that are proven to breed true. Breeding goals can still be established. The self-fertilization of F1 hybrids will often give rise to the variation needed in the F2 generation for selecting parents for subsequent generations, even if the characteristics of the original parents of the F1 hybrid are not known. It is in the following generations that fixed characteristics appear and the breeding of pure strains can begin. By selecting and crossing individuals that most nearly approach the “ideal” described by the (breeding goals), the variety can be continuously improved even if the exact patterns of inheritance are never determined. Complementary traits are eventually combined into one line whose seeds reproduce the favorable parental traits. Inbreeding strains also allows weak recessive traits to express themselves and these abnormalities must be diligently removed from the breeding population. After five or six generations, strains become amazingly uniform. Vigor is occasionally restored by crossing with other lines or by backcrossing.
Parental plants are selected which most nearly approach the ideal. If the parent does not express a desirable trait, it is much less likely to appear in the offspring. It is imperative that desirable characteristics be hereditary and not primarily the result of environment and cultivation. Acquired traits are not hereditary and cannot be made hereditary. Breeding for as few traits as possible at one time greatly increases the chance of success. In addition to the specific traits chosen as the aims of breeding, parents are selected which possess other generally desirable traits such as vigor and size. Determinations of dominance and recessiveness can only be made by observing the outcome of many crosses, although wild traits often tend to be dominant. This is one of the keys to adaptive survival. However, all the possible combinations will appear in the F2 generation if it is large enough, regardless of dominance.
Now, after further simplifying this wonderful system of inheritance, there are additional exceptions to the rules that must be explored. In some cases, a pair of genes may control a trait but a second or third pair of genes is needed to express this trait. This is known as gene interaction. No particular genetic attribute in which we may be interested is very isolated from other genes and the effects of environment. Genes are occasionally transferred in groups instead of assorting independently. This is known as gene linkage. These genes are spaced along the same chromosome and may or may not control the same trait. The result of linkage might be that one trait cannot be inherited without another. At times, traits are associated with the X and Y sex chromosomes and they may be limited to expression in only one sex (sex linkage). Crossing over also interferes with the analysis of crosses. Crossing over is the exchanging of entire pieces of genetic material between two chromosomes. This can result in two genes that are normally linked appearing on separate chromosomes where they will be independently inherited. All of these processes can cause crosses to deviate from the expected Mendel an outcome. Chance is a major factor in breeding medical marijuana, or any introduced plant, and the more crosses a breeder attempts the higher are the chances of success.
"Variate, isolate, intermate, evaluate, multiplicate, and disseminate are the key words in plant improvement. "
A plant breeder begins by producing or collecting various prospective parents from which the most desirable ones are selected and isolated. Intermating of the select parent’s results in offspring that must be evaluated for favorable characteristics. If evaluation indicates that the offspring are not improved, then the process is repeated. Improved offspring are multiplied and disseminated for commercial use. Further evaluation in the field is necessary to check for uniformity and to choose parents for further intermating. This cyclic approach provides a balanced system of plant improvement.
The basic nature of marijuana makes it challenging to breed. Wind pollination and dioecious sexuality, which account for the great adaptability in medical marijuana, cause many problems in breeding, but none of these is insurmountable. Developing a knowledge and feel for the plant is more important than memorizing Mendel an ratios. The words of the great Luther Burbank say it well, "heredity is indelibly fixed by repetition."
The first set of traits address marijuana plants as a whole while the remainder addresses the qualities of seedlings, leaves, fibers, and flowers. Finally, a list of various marijuana strains is provided along with specific characteristics. Following this order, basic and then specific selections of favorable characteristics can be made.
List of Favorable Traits of Marijuana (variation occurs)
General Traits:
Size and Yield
Vigor
Adaptability
Hardiness
Disease and Pest Resistance
Maturation
Root Production
Branching
Sex
Gross Phenotypes of Marijuana Strains
General Traits
a) Size and Yield - The size of an individual marijuana plant is determined by environmental factors such as room for root and shoot growth, adequate light and nutrients, and proper irrigation. These environmental factors influence the phenotypic image of genotype, but the genotype of the individual is responsible for overall variations in gross morphology, including size. Grown under the same conditions, particularly large and small individuals are easily spotted and selected. Many dwarf marijuana plants have been reported and dwarfism may be subject to genetic control, as it is in many higher plants, such as dwarf corn and citrus. Marijuana parents selected for large size tend to produce offspring of a larger average size each year. Hybrid crosses between tall (C. sativa-Mexico) strains and short (C. ruderalis-Russia) strains yield F1 offspring of intermediate height (Beutler and der Marderosian 1978). Hybrid vigor, however, will influence the size of offspring more than any other genetic factor. The increased size of hybrid offspring is often amazing and accounts for much of the success of marijuana cultivators in raising large plants. It is not known whether there is a set of genes for "gigantism" in marijuana or whether polyploid (cells containing more than two paired (homologous) sets of chromosomes) individuals really yield more than diploid (having a pair of each type of chromosome) due to increased chromosome count. Tetraploids (having four sets of chromosomes in each cell of the plant) tend to be taller and their water requirements are often higher than diploids. gene linkage yield is determined by the overall production of fiber, seed, or resin and selective breeding can be used to increase the yield of any one of these products. However, several of these traits may be closely related, and it may be impossible to breed for one without the other (gene linkage). Inbreeding of a pure strain increases yield only if high yield parents are selected. High yield plants, staminate or pistillate, are not finally selected until the plants are dried and manicured. Because of this, many of the most vigorous plants are crossed and seeds selected after harvest when the yield can be measured.
b) Vigor - Large size is often also a sign of healthy vigorous growth. A plant that begins to grow immediately will usually reach a larger size and produce a higher yield in a short growing season than a sluggish, slow-growing plant. Parents are always selected for rich green foliage and rapid, responsive growth. This will ensure that genes for certain weaknesses in overall growth and development are bred out of the population while genes for strength and vigor remain.
c) Adaptability - It is important for a plant with a wide distribution such as marijuana to be adaptable to many different environmental conditions. Indeed, Marijuana is one of the most genotypically diverse and phenotypically plastic plants on earth; as a result, it has adapted to environmental conditions ranging from equatorial to temperate climates. Domestic agricultural circumstances also dictate that marijuana must be grown under a great variety of conditions,
d) Hardiness - The hardiness of a plant is its overall resistance to heat and frost, drought and overwatering, and so on. Plants with a particular resistance appear when adverse conditions lead to the death of the rest of a large population. The surviving few members of the population might carry inheritable resistance to the environmental factor that destroyed the majority of the population. Breeding these survivors, subjecting the offspring to continuing stress conditions, and selecting carefully for several generations should result in a pure-breeding strain with increased resistance to drought, frost, or excessive heat.
e) Disease and Pest Resistance - In much the same way as for hardiness a strain may be bred for resistance to a certain disease, such as damping-off fungus. If flats of seedlings are infected by damping-off disease and nearly all of them die, the remaining few will have some resistance to damping-off fungus. If this resistance is inheritable, it can be passed on to subsequent generations by crossing these surviving plants. Subsequent crossing, tested by inoculating flats of seedling offspring with damping-off fungus, should yield a more resistant strain.
Resistance to pest attack works in much the same way. It is common to find stands of marijuana where one or a few plants are infested with insects while adjacent plants are untouched. Cannabinoid and terpenoid resins are most probably responsible for repelling insect attack, and levels of these vary from plant to plant. Marijuana has evolved defenses against insect attack in the form of resin-secreting glandular trichomes, which cover the reproductive and associated vegetative structures of mature plants. Insects, finding the resin disagreeable, rarely attack mature marijuana flowers. However, they may strip the outer leaves of the same plant because these develop fewer glandular trichomes and protective resins than the flowers. Non-glandular cannabinoids and other compounds produced within leaf and stem tissues which possibly inhibit insect attack, may account for the varying resistance of seedlings and vegetative juvenile plants to pest infestation. With the popularity of greenhouse marijuana cultivation, a strain is needed with increased resistance to mould, mite, aphid, or white fly infestation. These problems are often so severe that greenhouse cultivators destroy any plants that are attacked. Moulds usually reproduce by wind-borne spores, so negligence can rapidly lead to epidemic disaster. Selection and breeding of the least infected plants should result in strains with increased resistance.
f) Maturation - Control of the maturation of Marijuana is very important no matter what the reason for growing it. If marijuana is to be grown for fiber it is important that the maximum fiber content of the crop be reached early and that all of the individuals in the crop mature at the same time to facilitate commercial harvesting. Seed production requires the even maturation of both pollen and seed parents to ensure even setting and maturation of seeds. An uneven maturation of seeds would mean that some seeds would drop and be lost while others are still ripening. An understanding of floral maturation is the key to the production of high quality medical marijuana. Changes in gross morphology are accompanied by changes in cannabinoid and terpenoid production and serve as visual keys to determining the ripeness of marijuana flowers.
A Marijuana plant may mature either early or late, be fast or slow to flower, and ripen either evenly or sequentially.
Breeding for early or late maturation is certainly a reality; it is also possible to breed for fast or slow flowering and even for sequential ripening. In general, crosses between early-maturing plants give rise to early-maturing offspring, crosses between late-maturing plants give rise to late-maturing offspring, and crosses between late and early maturing plants give rise to offspring of intermediate maturation. This seems to indicate that maturation of marijuana is not controlled by the simple dominance and recessiveness of one gene but probably results from incomplete dominance and a combination of genes for separate aspects of maturation. For example, four separate genes control sorghum maturation. The sum of these genes produces a certain phenotype for maturation. Although breeders do not know the action of each specific gene, they still can breed for the total of these traits and achieve results more nearly approaching the goal of timely maturation than the parental strains.
g) Root Production - The size and shape of marijuana root systems vary greatly. Although every embryo sends out a taproot from which lateral roots grow, the individual growth pattern and final size and shape of the roots vary considerably. Some plants send out a deep taproot, up to one meter (39 inches) long, which helps support the plant against winds and rain. Most marijuana plants, however, produce a poor taproot that rarely extends more than thirty centimeters (1 foot). Lateral growth is responsible for most of the roots in marijuana plants. These fine lateral roots offer the plant additional support but their primary function is to absorb water and nutrients from the soil. A large root system can feed and support a large plant. Most lateral roots grow near the surface of the soil where there is more water, more oxygen, and nutrients that are more available. Breeding for root size and shape may prove beneficial for the production of large rain and wind resistant strains. Often marijuana plants, even very large ones, have very small and sensitive root systems. Recently, certain alkaloids have been discovered in the roots of marijuana that might have some medicinal value. If this proves the case, marijuana may be cultivated and bred for high alkaloid levels in the roots for use in the commercial production of pharmaceuticals.
As with many traits, it is difficult to make selections for root types until the parents are harvested. Because of this, many crosses are made early and seeds selected later.
h) Branching - The branching pattern of a marijuana plant is determined by the frequency of nodes along each branch and the extent of branching at each node. For examples, consider a tall, thin plant with slender limbs made up of long internodes and nodes with little branching (Oaxaca, Mexico strain). Compare this with a stout, densely branched plant with limbs of short internodes and highly branched nodes (Hindu Kush hashish strains). Different branching patterns are preferred for the different agricultural applications of fiber, flower, or resin production. Tall, thin plants with long internodes and no branching are best adapted to fiber production; short, broad plants with short inter nodes and well developed branching is best adapted to floral production. Branching structure is selected that will tolerate heavy rains and high winds without breaking. This is quite advantageous to outdoor growers in temperate zones with short seasons. Some breeders select tall, limber plants (Mexico) which bends in the wind; others select short, stiff plants (Hindu Kush) which resist the weight of water without bending.
i) Sex - Attempts to breed offspring of only one sexual type have led to more misunderstanding than any other facet of marijuana genetics. The discoveries of McPhee (1925) and Schaffner (1928) showed that pure sexual type and hermaphrodite conditions are inherited and that the percentage of sexual types could be altered by crossing with certain hermaphrodites. Since then researchers and breeders that a cross between ANY unselected hermaphrodite plant and a pistillate seed-parent should result in a population of all pistillate offspring have generally assumed it. This is not the case. In most cases, the offspring of hermaphrodite parents tend toward hermaphrodism, which is largely unfavorable for the production of marijuana other than fiber hemp. This is not to say that there is no tendency for hermaphrodite crosses to alter sex ratios in the offspring. The accidental release of some pollen from predominantly pistillate hermaphrodites, along with the complete eradication of nearly every staminate and staminate hermaphrodite plant may have led to a shift in sexual ratio in domestic populations of seedless drug marijuana. It is commonly observed that these strains tend toward sixty to eighty percent pistillate plants and a few pistillate hermaphrodites are not uncommon in these populations.
However, a cross-made which will produce nearly all pistillate or staminate individuals. If the proper pistillate hermaphrodite plant is selected as the (pollen-parent) and a pure pistillate plant is selected as the (seed-parent), it is possible to produce an F1, and subsequent generations, of nearly all pistillate offspring. The proper pistillate hermaphrodite (pollen-parent) is one which has grown as a pure pistillate plant and at the end of the season, or under artificial environmental stress, begins to develop a very few staminate flowers. If pollen from these few staminate flowers forming on a pistillate plant is applied to a pure pistillate seed parent, the resulting F1 generation should be almost all pistillate with only a few pistillate hermaphrodites. This will also be the case if the selected pistillate hermaphrodite pollen source is self-fertilized and bears its own seeds. Remember that a selfed (a form of asexual reproduction) hermaphrodite gives rise to more hermaphrodites, but a selfed pistillate plant that has given rise to a limited number of staminate flowers in response to environmental stresses should give rise to nearly all pistillate offspring. The F1 offspring may have a slight tendency to produce a few staminate flowers under further environmental stress and these used to produce F2 seed. A monoecious strain produces ninety-five (plus) percent plants with many pistillate and staminate flowers, but a dioecious strain produces ninety-five (plus) percent pure pistillate or staminate plants. A plant from a dioecious strain with a few inter sexual flowers is a pistillate or staminate hermaphrodite. Therefore, the difference between monoecism and her- maphrodism is one of degree, determined by genetics and environment.
Crosses may also be performed to produce nearly all staminate offspring. This is accomplished by crossing a pure staminate plant with a staminate plant that has produced a few pistillate flowers due to environmental stress. It is readily apparent that in the wild this is not a likely possibility. Very few staminate plants live long enough to produce pistillate flowers, and when this does happen the number of seeds produced is limited to the few pistillate flowers that occur. In the case of a pistillate hermaphrodite, it may produce only a few staminate flowers, but each of these may produce thousands of pollen grains, any one of which may fertilize one of the plentiful pistillate flowers, producing a seed. This is another reason that natural marijuana populations tend toward predominantly pistillate and pistillate hermaphrodite plants. Artificial hermaphrodites can be produced by hormone sprays, mutilation, and altered light cycles. These should prove most useful for fixing traits and sexual type.
Medical marijuana strains are selected for strong dioecious tendencies. Some breeders select strains with a sex ratio more nearly approaching one than a strain with a high pistillate sex ratio. They believe this reduces the chances of pistillate plants turning hermaphrodite later in the season.
It is feared that many of the world's finest strains of marijuana have been or may be lost forever due to hybridization with foreign marijuana populations and the socio-economic displacement of marijuana cultures worldwide. Collectors and breeders need to preserve these rare and endangered gene pools before it is too late.
Various combinations of these traits are possible and inevitable. The traits that we most often see are most likely dominant and the improvement of marijuana strains through breeding is most easily accomplished by concentrating on the dominant phenotypes for the most important traits. The best breeders set high goals of limited scope and adhere to their ideals.
Cannabinoid Biosynthesis
Since resin, secretion and associated terpenoid and cannabinoid biosynthesis are at their peak just after the pistils have begun to turn brown but before the calyx stops growing, it seems obvious that floral clusters should be harvested during this time. More subtle variations in terpenoid and cannabinoid levels also take place within this period of maximum resin secretion, and these variations influence the nature of the resin’s psychoactive effect.
The cannabinoid ratios characteristic of a strain are primarily determined by genes, but it must be remembered that many environmental factors, such as light, temperature, and humidity, influence the path of a molecule along the cannabinoid biosynthetic pathway. These environmental factors can cause an atypical final cannabinoid profile (cannabinoid levels and ratios). Not all cannabinoid molecules begin their journey through the pathway at the same time, nor do all of them complete the cycle and turn into THC molecules simultaneously. There is no magical way to influence the cannabinoid biosynthesis to favor THC production, but certain factors involved in the growth and maturation of marijuana do affect final cannabinoid levels. These factors can be controlled to some extent by proper selection of mature floral clusters for harvesting, agricultural technique, and local environment. In addition to genetic and seasonal influences, the picture is further modified by the fact that each individual calyx goes through the cannabinoid cycle independently and that during peak periods of resin secretion new flowers is produced every day and begins their own cycle. This means that at any given time the ratio of calyx-to-leaf, the average calyx condition, the condition of the resins, and resultant cannabinoid ratios indicate which stage the floral cluster has reached. Since it is difficult for the amateur cultivator to determine the cannabinoid profile of a floral cluster without chromatographic analysis, this discussion will center on the known and theoretical correlations between the external characteristics of calyx and resin and internal cannabinoid profile. Actually, THC acid and the other necessary cannabinoid acids are not psychoactive until they decarboxylate (degrade) (lose an acidic carboxyl group [COOHI). It is the cannabinoid acids that move along the biosynthetic pathway, and these acids undergo the strategic reactions that determine the position of any particular cannabinoid molecule along the pathway. After the resins are secreted by the glandular trichome they begin to harden and the cannabinoid acids begin to decarboxylate. Any remaining cannabinoid acids are decarboxylated by heat within a few days after harvesting. Other THC acids with shorter side-chains also occur in certain strains of marijuana. Several are known to be psychoactive and many more are suspected of psychoactivity. The shorter propyl (three-carbon) and methyl (one-carbon) side-chain homolog’s (similarly shaped molecules) are shorter acting than pentyl (five-carbon) THCs and may account for some of the quick, flashy effects noted by some marijuana users. The first step in the pentyl cannabinoid biosynthetic pathway is the combination of olivetolic acid with geranyl pyrophosphate. Molecules are derived from
terpenes, and it is readily apparent that the biosynthetic route of the aromatic terpenoids may be a clue to formation of the cannabinoids. The union of these two molecules forms CBG acid (cannabigerolic acid) which is the basic cannabinoid precursor molecule. mCBG acid may be converted to CBGM (CBG acid monomethyl ether), or a hydroxyl group (OH) attaches to the
geraniol portion of the molecule forming hydroxy-CBG acid. Through the either formation of a transition-state molecule, CBC acid (cannabichromenic acid) or CBD acid (cannabidiolic acid) is formed. CBD acid is the precursor to the THC acids and although CBD is only mildly psychoactive by itself, it may act with THC to modify the psychoactive effect of the THC in a sedative way. CBC is also mildly psychoactive and may interact synergistically with THC to alter the psychoactive effect (Turner et al. 1975). Indeed, CBD may suppress the effect of THC and CBC may potentiate the effect of THC, although this has not yet been proven. All of the reactions along the cannabinoid biosynthetic pathway are enzyme-controlled but are also affected by environmental conditions.
Conversion of CBD acid to THC acid is the single most important reaction with respect to psychoactivity in the entire pathway and the one about which we know the most. Raphael Mechoulam studied the role of ultraviolet light in the biosynthesis of THC acids and minor cannabinoids. In the laboratory, Mechoulam converted CBD acid to THC acids by exposing a solution of CBD acid in n-hexane to ultraviolet light of 235-285 nm. (up to 48 hours). This reaction uses atmospheric oxygen molecules (02) and is irreversible; however, the yield of the conversion is only about fifteen percent THC acid, and some of the products formed in the laboratory experiment do not occur in living specimens. Total psycho-activity is attributed to the ratios of the primary cannabinoids of CBC, CBD, THC and CBN; the ratios of methyl, propyl, and pentyl homolog’s of these cannabinoids; and the isomeric variations of each of these cannabinoids. Myriad subtle combinations are sure to exist. Terpenoid and other aromatic compounds might suppress or potentiate the effects of THCs.
Environmental conditions influence cannabinoid biosynthesis by modifying enzymatic systems and the resultant potency of marijuana. High altitude environments are often more arid and exposed to more intense sunlight than lower environments. Recent studies by Mobarak et al. (1978) of Marijuana grown in Afghanistan at 1,300 meters (4,350 feet) elevation show that significantly more propyl cannabinoids are formed than the respective pentyl homologs. Other strains from this area of Asia have also exhibited the presence of propyl cannabinoids, but it cannot be discounted that altitude might influence which path of cannabinoid biosynthesis is favored. Aridity favors resin production and total cannabinoid production; however, it is unknown whether arid conditions promote THC production specifically. It is suspected that increased ultraviolet radiation might affect cannabinoid production directly. Ultra-violet light participates in the biosynthesis of THC acids from CBD acids, the conversion of CBC acids to CCY acids, and the conversion of CBD acids to CBS acids. However, it is unknown whether increased ultraviolet light might shift cannabinoid synthesis from pentyl to propyl pathways or influence the production of THC acid or CBC acid instead of CBD acid.
Small and others have used the ratio of THC to CBD in chemotype determination. The genetically determined inability of certain strains to convert CBD acid to THC acid makes them a member of a fiber chemo type, but if a strain has the genetically determined ability to convert CBD acid to THC acid then it is considered a drug strain. It is also interesting to note that Turner and Hadley (1973) discovered an African strain with a very high THC level and no CBD although there are fair amounts of CBC acid present in the strain. Turner states that he has seen several strains totally devoid of CBD, but he has never seen a strain totally devoid of THC. In addition, many early authors confused CBC with CBD in analyzed samples because of the proximity of their peaks on gas liquid chromatography (GLC) results. If the biosynthetic pathway needs alteration to include an enzymatically controlled system involving the direct conversion of hydroxy-CBG acid to THC acid through allelic rearrangement of hydroxyl-CBG acid and cyclization of the rearranged intermediate to THC acid, as Turner and Hadley (1973) suggest, then CBD acid would be bypassed in the cycle and its absence explained. Another possibility is that, since CBC acid is formed from the same symmetric intermediate that is allylically rearranged before forming CBD acid, CBC acid may be the accumulated intermediate, the reaction may be reversed, and through the symmetric intermediate and the usual allelic rearrangement CBD acid would be formed but directly converted to THC acid by a similar enzyme system to that which reversed the formation of CBC acid. If this happened fast, enough no CBD acid would be detected. It is more likely, however, that CBDA in drug strains is converted directly to THCA as soon as it is formed and no CBD builds up. Turner, Hemphill, and Mahlberg (1978) found that CBC acid was contained in the tissues of marijuana but not in the resin secreted by the glandular trichomes. In any event, these possible deviations from the accepted biosynthetic pathway provide us with something to think about. It is rather complicated trying to decipher the mysteries of marijuana strains and varieties.
Returning to the more orthodox version of the cannabinoid biosynthesis, the role of ultraviolet light is very important. It seems apparent that ultraviolet light, normally supplied in abundance by sunlight, takes part in the conversion of CBD acid to THC acids. The degradation is accomplished primarily by heat and light and is not enzymatically controlled by the plant. CBN is also suspected of synergistic modification of the psychoactivity THC’s. The cannabinoid balance between CBC, CBD, THC, and CBN is determined by genetics and maturation. THC production is an ongoing process as long as the glandular trichome remains active. Variations in the level of THC in the same trichome as it matures are the result of THC acid being broken down to CBN acid while CBD acid is converted to THC acid. If the rate of THC biosynthesis exceeds the rate of THC breakdown, the THC level in the trichomes raises; if the breakdown rate is faster than the rate of biosynthesis, the THC level drops. Clear or slightly amber transparent resin is a sign that the glandular trichome is still active. As soon as resin secretion begins to slow, the resins will usually polymerize and harden. During the late floral stages, the resin tends to darken to a transparent amber color. If it begins to deteriorate, it first turns translucent and then opaque brown or white. Near-freezing temperatures during maturation will often result in opaque white resins. During active secretion, THC acids are constantly being formed from CBD acid and breaking down into CBN acid.
It is feared that many of the world's finest strains of marijuana have been or may be lost forever due to hybridization with foreign marijuana populations and the socio-economic displacement of marijuana cultures worldwide. Collectors and breeders need to preserve these rare and endangered gene pools before it is too late.
Various combinations of these traits are possible and inevitable. The traits that we most often see are most likely dominant and the improvement of marijuana strains through breeding is most easily accomplished by concentrating on the dominant phenotypes for the most important traits. The best breeders set high goals of limited scope and adhere to their ideals.
Cannabinoid Biosynthesis
Since resin, secretion and associated terpenoid and cannabinoid biosynthesis are at their peak just after the pistils have begun to turn brown but before the calyx stops growing, it seems obvious that floral clusters should be harvested during this time. More subtle variations in terpenoid and cannabinoid levels also take place within this period of maximum resin secretion, and these variations influence the nature of the resin’s psychoactive effect.
The cannabinoid ratios characteristic of a strain are primarily determined by genes, but it must be remembered that many environmental factors, such as light, temperature, and humidity, influence the path of a molecule along the cannabinoid biosynthetic pathway. These environmental factors can cause an atypical final cannabinoid profile (cannabinoid levels and ratios). Not all cannabinoid molecules begin their journey through the pathway at the same time, nor do all of them complete the cycle and turn into THC molecules simultaneously. There is no magical way to influence the cannabinoid biosynthesis to favor THC production, but certain factors involved in the growth and maturation of marijuana do affect final cannabinoid levels. These factors can be controlled to some extent by proper selection of mature floral clusters for harvesting, agricultural technique, and local environment. In addition to genetic and seasonal influences, the picture is further modified by the fact that each individual calyx goes through the cannabinoid cycle independently and that during peak periods of resin secretion new flowers is produced every day and begins their own cycle. This means that at any given time the ratio of calyx-to-leaf, the average calyx condition, the condition of the resins, and resultant cannabinoid ratios indicate which stage the floral cluster has reached. Since it is difficult for the amateur cultivator to determine the cannabinoid profile of a floral cluster without chromatographic analysis, this discussion will center on the known and theoretical correlations between the external characteristics of calyx and resin and internal cannabinoid profile. Actually, THC acid and the other necessary cannabinoid acids are not psychoactive until they decarboxylate (degrade) (lose an acidic carboxyl group [COOHI). It is the cannabinoid acids that move along the biosynthetic pathway, and these acids undergo the strategic reactions that determine the position of any particular cannabinoid molecule along the pathway. After the resins are secreted by the glandular trichome they begin to harden and the cannabinoid acids begin to decarboxylate. Any remaining cannabinoid acids are decarboxylated by heat within a few days after harvesting. Other THC acids with shorter side-chains also occur in certain strains of marijuana. Several are known to be psychoactive and many more are suspected of psychoactivity. The shorter propyl (three-carbon) and methyl (one-carbon) side-chain homolog’s (similarly shaped molecules) are shorter acting than pentyl (five-carbon) THCs and may account for some of the quick, flashy effects noted by some marijuana users. The first step in the pentyl cannabinoid biosynthetic pathway is the combination of olivetolic acid with geranyl pyrophosphate. Molecules are derived from
terpenes, and it is readily apparent that the biosynthetic route of the aromatic terpenoids may be a clue to formation of the cannabinoids. The union of these two molecules forms CBG acid (cannabigerolic acid) which is the basic cannabinoid precursor molecule. mCBG acid may be converted to CBGM (CBG acid monomethyl ether), or a hydroxyl group (OH) attaches to the
geraniol portion of the molecule forming hydroxy-CBG acid. Through the either formation of a transition-state molecule, CBC acid (cannabichromenic acid) or CBD acid (cannabidiolic acid) is formed. CBD acid is the precursor to the THC acids and although CBD is only mildly psychoactive by itself, it may act with THC to modify the psychoactive effect of the THC in a sedative way. CBC is also mildly psychoactive and may interact synergistically with THC to alter the psychoactive effect (Turner et al. 1975). Indeed, CBD may suppress the effect of THC and CBC may potentiate the effect of THC, although this has not yet been proven. All of the reactions along the cannabinoid biosynthetic pathway are enzyme-controlled but are also affected by environmental conditions.
Conversion of CBD acid to THC acid is the single most important reaction with respect to psychoactivity in the entire pathway and the one about which we know the most. Raphael Mechoulam studied the role of ultraviolet light in the biosynthesis of THC acids and minor cannabinoids. In the laboratory, Mechoulam converted CBD acid to THC acids by exposing a solution of CBD acid in n-hexane to ultraviolet light of 235-285 nm. (up to 48 hours). This reaction uses atmospheric oxygen molecules (02) and is irreversible; however, the yield of the conversion is only about fifteen percent THC acid, and some of the products formed in the laboratory experiment do not occur in living specimens. Total psycho-activity is attributed to the ratios of the primary cannabinoids of CBC, CBD, THC and CBN; the ratios of methyl, propyl, and pentyl homolog’s of these cannabinoids; and the isomeric variations of each of these cannabinoids. Myriad subtle combinations are sure to exist. Terpenoid and other aromatic compounds might suppress or potentiate the effects of THCs.
Environmental conditions influence cannabinoid biosynthesis by modifying enzymatic systems and the resultant potency of marijuana. High altitude environments are often more arid and exposed to more intense sunlight than lower environments. Recent studies by Mobarak et al. (1978) of Marijuana grown in Afghanistan at 1,300 meters (4,350 feet) elevation show that significantly more propyl cannabinoids are formed than the respective pentyl homologs. Other strains from this area of Asia have also exhibited the presence of propyl cannabinoids, but it cannot be discounted that altitude might influence which path of cannabinoid biosynthesis is favored. Aridity favors resin production and total cannabinoid production; however, it is unknown whether arid conditions promote THC production specifically. It is suspected that increased ultraviolet radiation might affect cannabinoid production directly. Ultra-violet light participates in the biosynthesis of THC acids from CBD acids, the conversion of CBC acids to CCY acids, and the conversion of CBD acids to CBS acids. However, it is unknown whether increased ultraviolet light might shift cannabinoid synthesis from pentyl to propyl pathways or influence the production of THC acid or CBC acid instead of CBD acid.
Small and others have used the ratio of THC to CBD in chemotype determination. The genetically determined inability of certain strains to convert CBD acid to THC acid makes them a member of a fiber chemo type, but if a strain has the genetically determined ability to convert CBD acid to THC acid then it is considered a drug strain. It is also interesting to note that Turner and Hadley (1973) discovered an African strain with a very high THC level and no CBD although there are fair amounts of CBC acid present in the strain. Turner states that he has seen several strains totally devoid of CBD, but he has never seen a strain totally devoid of THC. In addition, many early authors confused CBC with CBD in analyzed samples because of the proximity of their peaks on gas liquid chromatography (GLC) results. If the biosynthetic pathway needs alteration to include an enzymatically controlled system involving the direct conversion of hydroxy-CBG acid to THC acid through allelic rearrangement of hydroxyl-CBG acid and cyclization of the rearranged intermediate to THC acid, as Turner and Hadley (1973) suggest, then CBD acid would be bypassed in the cycle and its absence explained. Another possibility is that, since CBC acid is formed from the same symmetric intermediate that is allylically rearranged before forming CBD acid, CBC acid may be the accumulated intermediate, the reaction may be reversed, and through the symmetric intermediate and the usual allelic rearrangement CBD acid would be formed but directly converted to THC acid by a similar enzyme system to that which reversed the formation of CBC acid. If this happened fast, enough no CBD acid would be detected. It is more likely, however, that CBDA in drug strains is converted directly to THCA as soon as it is formed and no CBD builds up. Turner, Hemphill, and Mahlberg (1978) found that CBC acid was contained in the tissues of marijuana but not in the resin secreted by the glandular trichomes. In any event, these possible deviations from the accepted biosynthetic pathway provide us with something to think about. It is rather complicated trying to decipher the mysteries of marijuana strains and varieties.
Returning to the more orthodox version of the cannabinoid biosynthesis, the role of ultraviolet light is very important. It seems apparent that ultraviolet light, normally supplied in abundance by sunlight, takes part in the conversion of CBD acid to THC acids. The degradation is accomplished primarily by heat and light and is not enzymatically controlled by the plant. CBN is also suspected of synergistic modification of the psychoactivity THC’s. The cannabinoid balance between CBC, CBD, THC, and CBN is determined by genetics and maturation. THC production is an ongoing process as long as the glandular trichome remains active. Variations in the level of THC in the same trichome as it matures are the result of THC acid being broken down to CBN acid while CBD acid is converted to THC acid. If the rate of THC biosynthesis exceeds the rate of THC breakdown, the THC level in the trichomes raises; if the breakdown rate is faster than the rate of biosynthesis, the THC level drops. Clear or slightly amber transparent resin is a sign that the glandular trichome is still active. As soon as resin secretion begins to slow, the resins will usually polymerize and harden. During the late floral stages, the resin tends to darken to a transparent amber color. If it begins to deteriorate, it first turns translucent and then opaque brown or white. Near-freezing temperatures during maturation will often result in opaque white resins. During active secretion, THC acids are constantly being formed from CBD acid and breaking down into CBN acid.
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