At the present moment, the modern feminized and photoperiod-dependent marijuana strains represent the maximum exponent of marijuana breeding, reaching to extraordinary levels of quality never seen before. Exquisite and varied tastes and aromas that are well defined and differentiated, combine with distinctive chemotypes (terpene and cannabinoid profiles) to delight cannabis users from around the world; a world where new horizons are opening for the medicinal uses of marijuana and for the regulation of its recreational use.
What are photoperiod-dependent strains?
Photoperiod-dependent seeds produce cannabis plants that flower depending on the amount of light and darkness that they receive (photoperiod).
Photoperiod-dependent strains start flowering depending on the hours of light and darkness that they receive. In this group we can find all the feminized and regular genetics that we were used to grow until the arrival of the autoflowering strains. When grown outdoors these genetics flower in a determined season of the year, when the hours of light decrease and the hours of darkness increase. This is usually by the end of the Summer or in the course of the Autumn. When grown indoors, with artificial light, they start flowering when we give them 12 hours of light and 12 hours of darkness.
The immense majority of cannabis strains are photoperiod dependent, so the beginning of flowering is triggered by the arrival of short days and long nights, which means that it is the photoperiod that determines the beginning of flowering.
Feminized or Photoperiod-dependent seeds?
Photoperiod-dependent seeds are erroneously denominated by a lot of seed banks and cannabis users as “feminized seeds”. This is an incorrect use for this expression. The definition of “Feminized Seed” refers to the sex of the population of seeds. These are seed populations that only produce female plants, known in genetic terminology as gynoecious lines. These seeds are denominated as “feminized seeds” to differentiate them from the seeds known as “regular seeds” that produce males and females. The denomination “photoperiod-dependent seed” or “autoflowering seed” refers to the two different ways how flowering can be triggered in marihuana plants, depending on the photoperiod in photoperiod-dependent plants or automatically when reaching to a certain age in autoflowering plants. This is to say, a variety is whether feminized or regular and, on the other hand, it is photoperiod dependent or autoflowering, but it is not correct to call “feminized seeds” to photoperiod-dependent seeds because the autoflowering seeds can also be feminized, just like all the autoflowering strains from the Sweet Seeds®’ catalog.
Photoperiod-dependent F1 Fast Version® seeds
The F1 Fast Version® strains are the first filial generation (F1) resulting from the cross (hybridization) between a photoperiod-dependent strain and an autoflowering strain. The result of this hybridization between two totally different plants (at least regarding to the type of flowering) is know in genetic terminology as “F1 Hybrid”. They are hybrid genetics, 100% photoperiod dependent, but featuring a very fast flowering stage. The photoperiod-dependent parental contributes to the F1 hybrid with its condition of photoperiod dependent to all the offspring and the autoflowering genetic contributes to the F1 hybrid with super-fast flowering and maturation of the buds to all the offspring.
The F1 Hybrids combine within the same generation the so appreciated “stability” and “hybrid vigor”.
These faster strains suppose an economy in time, resources and efforts. Besides that, the fast flowering of these genetics is an important bonus that can be used by those growers who cultivate in humid or rainy zones with harsh winters, because these plants can anticipate their maturity to the most virulent season of fungal attacks or to the arrival of bad weather and cold.
Advantages of growing photoperiod-dependent seeds
In the same way that autoflowering seeds feature some advantages over photoperiod-dependent seeds, the photoperiod-dependent seeds also feature some advantages over the autoflowering seeds. Here are some of this advantages:
- Preserving Mother Plants: One of the main advantages of growing photoperiod-dependent seeds is the possibility of preserving, indefinitely, clones of any special plant that we have found. This is usually performed by keeping the clones under artificial light with a photoperiod of 18h of light and 6h of darkness. With this photoperiod the plants remain in vegetative stage without ever giving way into flowering and they are used to extract clones from them.
- Vegetative Propagation: Photoperiod-dependent plants can be multiplied in our garden by simply taking clones from our plant from seed or from our mother plant.
- Height control, size and production: by keeping the photoperiod-dependent plants in a vegetative growth photoperiod enough time to reach to the desired height, we can control the height and size of the plants to get big plants and to get a high yield of buds. Outdoors, this allows us to get our annual auto-supply of weed with very few plants. In the same way, controlling the photoperiod to induce flowering without any vegetative growth we will obtain the inverse effect: short plants, discreet and with a fast life cycle. To planify the desirable height we have to take in consideration that, depending on the strain, the plants may duplicate, triplicate or even quadruplicate the height that they presented in the beginning of flowering or since we changed the photoperiod in indoor grows.
The Sweet Seeds®’ breeding philosophy
Due to an unfair prohibition and to the globalization phenomenon, both wild and domesticated marihuana have been suffering along the last 100 years a massive extinction. For a lot of these unique marihuana strains it is already too late and it is impossible to recover them. This biodiversity loss is an unjustifiable incident and means a huge loss of natural resources for the planet. The unique genetic code of each vegetal variety is a living laboratory that could open the door to future knowledge and discoveries. It could be a huge help in the so important medical, energetic and industrial challenges that humanity has to face in this XXI century.
At Sweet Seeds® we think that the best way to protect cannabis for the future, when this unfair and irrational persecution that weighs on the marihuana plant is finished, is preserving and increasing its diversity, as well as distributing its seeds.
Our breeding philosophy is simple: the breeders of Sweet Seeds® are cannabis users and collectors of genetics. We search and select the best genetics that cross our path to preserve them indefinitely so we can enjoy them today, tomorrow or for the rest of our lives. We work with the conviction that in about 200 years, future generations will enjoy the result of our work, which is our great passion at the same time.
The criteria used to select our best mothers is mainly focused in the desirable qualities of these plants and not in their origin or pedigree. The parentals we use in Sweet Seeds® are the result of twenty years of research, selection, conservation and development.
Plants that are easy to grow and allow for high production of flowers and trichomes with special and pleasant aromas have always been symbols of identity of our genetic collection.
At Sweet Seeds® we run a pioneer seed bank in the development and improvement of modern feminized photoperiod-dependent seeds. We believed in these new feminized genetics since the first time we reproduced our beloved female plants by crossing them with each other, obtaining our first feminized seeds.
Breeding photoperiod-dependent varieties
Sweet Seeds®’ varieties, are the result of classic breeding programs. In these programs we work by crossing, reproducing and selecting the different genetics until we obtain satisfactory results and in accordance with the objectives pursued. These breeding programs are aimed at the selection and stabilization of desirable agronomic and botanical characteristics (internodal distance, bud density, etc.), chemotypic (cannabinoid and terpene profile) and organoleptic characteristics (flavors and aromas), combined with the elimination of undesirable traits if any occur.
The Sweet Seeds®’ breeders always paid special attention to the selection and stabilization of organoleptic traits. All our varieties are especially aromatic and tasty. This is a hallmark of our seed bank and the reason it is called "Sweet Seeds®". For us, taste and aroma are as important as the cannabinoid levels, the amount of resin or other desirable traits.
For the production of feminized photoperiod-dependent "commercial" seeds (those that are intended for sale to the public), in Sweet Seeds® we use selected "elite clones". "Clonal selection" plays a key role in most cannabis genetic improvement programs.
Elite clones are the result of an intense selection of the best specimens at the end of breeding programs or the result of the search and collection of new exceptional genetics that are used as starting material in breeding programs. These elite clones are preserved in our "bank of mothers" and are the best female cannabis plants that crossed our way throughout our life as cannabis growers, breeders and genetic collectors. Besides gathering a lot of interesting traits for the cannabis grower, these elite clones show a good tendency to produce good hybrids and also respond well to the sex reversal technique necessary to produce feminized seeds.
To produce the commercial seed of each variety we always use the same clones. Always using the same parentals has its benefits. This way the results are totally predictable, since they are known in advance and will always be the same, unequivocally allowing to guarantee the quality of the obtained seeds. We only replace parentals when we find an elite clone that contributes with better traits to the offspring, while maintaining the characteristic features of the variety, and replacing parentals is not usual at all.
On the contrary, when working with autoflowering genetics we can not save the best specimens we have found in clone form and we have to work with seed populations. This forces the breeders of autoflowering varieties to constantly select the parentals not only in the development of the breeding program but also each time they reproduce the commercial seeds. Depending on the chosen parentals in each generation, these populations may experience genetic drifts in one direction or another, thus not maintaining the constant gene frequencies in the commercial seed. In recent years, these populations of autoflowering seeds have been kept in constant evolution and improvement.
When it comes to F1 Fast Version® seeds, they are the first filial generation resulting from the cross between an elite clone from the Sweet Seeds®’ bank of mothers and a selected genetic line from the latest generation of autoflowering seeds. They are F1 Hybrids. This first generation is always commercialized, since it is the only one that is 100% uniform for the photoperiod-dependent characteristic and 100% fast flowering. The process is relatively simple, the difficulty lies in the selection of the parentals. The parentals we use in Sweet Seeds® are the result of twenty years of research, selection, conservation and development.
Hybridization is the most commonly used technique in the development of our photoperiod-dependent varieties, with the goal of improving the hybrid vigor and bringing uniformity to the offspring.
Hybridization is one of the most important and fruitful methods of genetic improvement and one of the most used by cannabis seed banks. It allows to quickly gather the desirable characteristics of both parentals, in addition to pursuing the goal of taking advantage of the phenomenon known as hybrid vigor or heterosis. This hybrid vigor is usually expressed in characters from the quantitative type. By other words, characters that are measurable. In marihuana they are usually expressed as a:
- Increase in yield
- Better adaptation to the environment
- Better resistance to plagues and diseases
- Better tolerance to environmental stresses
- Increase in the speed of growth
- Higher precocity (Reduction in the necessary time to achieve maturity)
- A general increase in size of buds, stems, leaves, etc…
- Increase in the total number of nodes, leaves, flowers, trichomes, etc…
- Increase in the total amount of terpenes and cannabinoids
Not all vegetal species present the phenomenon of hybrid vigor, although it is quite usual in the plant kingdom and for our fortune it is expressed with greater intensity in the allogamous species, which is the case of marijuana. The greater the genetic distance between the parentals, the greater the heterosis or hybrid vigor.
In contrast to hybridization, the self-pollination technique is used to reproduce the special and desirable characteristics of an elite clone without contaminating it with external genetics. This technique provides great stability to the offspring and successive generations.
This technique was used in one of our first feminized and photoperiod-dependent varieties, our S. A. D. Sweet Afgani Delicious S1® (SWS02).
Self-fertilization produces generations of seeds that tend very quickly to homozygosis and is one of the traditional methods to obtain pure lines in allogamous plants, which is the case of cannabis. With each generation of self-fertilization 50% of the genes found in heterozygosis become homozygous.
The technique we use to perform self-pollination with a female clone is the same technique we use to get feminized seeds. It involves getting viable pollen from a female clone and then using this pollen to pollinate another female clone from the same mother plant. To obtain pollen from female plants we use a sex reversion technique that involves applying a product based on Silver Thiosulphate to the plant. This application induces the production of male flowers, and in the appropriate dose and form of application the production of abundant and viable pollen in a female plant.
Self-pollination is a relatively recent improvement technique in the improvement of cannabis varieties because before the discovery of sex reversion techniques it was impossible to apply these techniques of improvement without dragging genes of hermaphroditism towards the offspring. The only possible way to self-pollinate a female cannabis plant without using sex reversion techniques would be by using female individuals who would show a male flower under stress or automatically, in order for this pollen to self-pollinate the plant. But with this procedure we would be applying selective pressure on the group of plants that most easily show traits of hermaphroditism under stress, and this is of no interest in the case of cannabis.
With the modern techniques of sex reversion these plants that show some hermaphroditism traits under stress are eliminated of any project of feminized varieties improvement. Even if the clone is excellent, the goal is to produce 100% feminized varieties and for that it is mandatory to choose "elite clones" (clonal selection) with zero or almost no tendency to produce male flowers under stress. These plants are known as "pure females".
With this, cannabis breeders can open new ways of breeding and improvement with self-pollination and all the other improvement techniques that imply self-pollinations, such as "recurrent selection", for example. It is now possible to explore these techniques without dragging the genes of hermaphroditism, by making selective pressure on the interesting characters and excluding all the genes that promote hermaphroditism in each generation from the genetic pool, looking for those known as pure females in the cannabic world.
The letter “S” is used in the notation that identifies self-pollinations. In S1, the number indicates that we are talking about the first filial generation of a self-pollination.
Other breeding techniques used in our photoperiod-dependent varieties
Massal Selection and its variants: It consists in the selection of the individuals that show the characteristics sought and the exclusion of the undesired individuals. The crossing of these selected individuals will produce the seed with which the next generation is sown. This process is repeated until we get a population in which the sought characteristics are gathered. This technique has numerous variants and is often used along with other techniques in the improvement programs.
Synthetic varieties: Synthetic varieties are populations created by cross-pollination of several different genetic lines, in a balanced way and in isolation. Then, successive generations are multiplied also in isolation and in a balanced way. Our appreciated Cream Caramel® (SWS04) is a result of this technique.
Synthetic varieties and hybrid varieties share the objective of taking advantage of the hybrid vigor and providing homogeneity to the offspring, further fixing the most desirable characteristics by selection in successive generations.
Breeding our Cream Caramel® (SWS04)
In the development of this line we used a classic improvement method that can be applied to allogamous or partially allogamous species, which is the case of cannabis. In genetic terminology, this class of cultivars are known as Synthetic Varieties (V.S.).
Cream Caramel® (SWS04) is the result of the balanced mix of several of our best Indicas, chosen for its excellent agronomic, botanical and chemotypic qualities, such as production, type and intensity of the aroma, type and intensity of effect, plant structure, short flowering, number of trichomes, resistance to diseases, null tendency to hermaphroditism and, above all, also attending to their good qualities to create good hybrids.
To create Cream Caramel®, the three mainly indica genetic lines used were a BlueBlack hybrid (Blueberry ’99 x Black Domina ’98), a very special Maple Leaf Indica and a remarkably medicinal White Rhino developed in the Netherlands. Three lines that allowed for the formation of a balanced population composed by an equal number of specimens of each of the parental lines. Later on, we isolated each group of plants from the same strain to avoid any undesired self-pollination and to promote crossed pollination, making the most out of the heterosis (or hybrid vigour) and leaving them free for inter-pollination with only the other two parental lines.
All the plants from the three pollination chambers were then harvested and the seeds obtained from this first generation were mixed in equal number, forming a new generation containing all the possible hybrid combinations from the founding genetic lines. This generation, which we can designate by VS1, was then left to open pollination inside a closed chamber to avoid contamination with outside pollens. With this procedure we obtained a cross with all the possible hybrid combinations (VS2).
In this second generation, VS2, the seeds were created through random combinations of gametes from the three parental lines. These individuals are a well balanced panmictic population and all the following generations will be identical (if bred in open pollination and absence of selection) as the genic rates remain constant. In the following generations until VS5 we performed “massal selection” by choosing a high number of plants with very interesting agronomical characteristics to progress to the next generation, instead of leaving the process totally at random.
Cream Caramel® is a V.S. which shares with the hybrid varieties the goal of providing hybrid vigor and bringing homogeneity to the offspring, further fixing the most desirable traits through selection in successive generations. After five generations of free pollination and selection, the result is Cream Caramel®, a very stable and productive variety, featuring intense aroma and abundant resin, very adaptable to unfavorable conditions and environmental adversities (cold, drought, etc.) due to its great genetic bandwidth that gives Cream Caramel® a genetic flexibility to adapt to the medium that is even greater than in F1 Hybrids.
In order to obtain Cream Caramel®, as in the case of the other photoperiod-dependent varieties from the Sweet Seeds®’ collection, no males have been used in the fertilization, but modern methods of sex reversion have been applied to selected female plants, thus obtaining a V.S. which features a female offspring of around 99.9%.