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high cbd marijuana seeds

Copyright © 2021 Flajšman, Slapnik and Murovec.

The use of the cannabis plant as a source of therapeutic compounds is gaining great importance since restrictions on its growth and use are gradually reduced throughout the world. Intensification of medical (drug type) cannabis production stimulated breeding activities aimed at developing new, improved cultivars with precisely defined, and stable cannabinoid profiles. The effects of several exogenous substances, known to be involved in sex expressions, such as silver thiosulfate (STS), gibberellic acid (GA), and colloidal silver, were analyzed in this study. Various concentrations were tested within 23 different treatments on two high cannabidiol (CBD) breeding populations. Our results showed that spraying whole plants with STS once is more efficient than the application of STS on shoot tips while spraying plants with 0.01% GA and intensive cutting is ineffective in stimulating the production of male flowers. Additionally, spraying whole plants with colloidal silver was also shown to be effective in the induction of male flowers on female plants, since it produced up to 379 male flowers per plant. The viability and fertility of the induced male flowers were confirmed by fluorescein diacetate (FDA) staining of pollen grains, in vitro and in vivo germination tests of pollen, counting the number of seeds developed after hybridization, and evaluating germination rates of developed seeds. Finally, one established protocol was implemented for crossing selected female plants. The cannabinoid profile of the progeny was compared with the profile of the parental population and an improvement in the biochemical profile of the breeding population was confirmed. The progeny had a higher and more uniform total CBD (tCBD) to total tetrahydrocannabinol (tTHC) ratio (up to 29.6; average 21.33 ± 0.39) compared with the original population (up to 18.8; average 7.83 ± 1.03). This is the first comprehensive report on the induction of fertile male flowers on female plants from dioecious medical cannabis (Cannabis sativa L.).

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Keywords: Cannabis sativa L.; cannabidiol; cannabinoids; feminized seed; high CBD medical cannabis; sex manipulation; silver thiosulfate.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Conflict of interest statement

High cbd marijuana seeds

Finally, the protocol using colloidal silver was successfully used for breeding female plants of medical cannabis breeding population MX-CBD-707. Entirely, the female progeny was obtained after crossing the parental population of females induced to form male flowers, thus confirming the theory of producing exclusively feminized seeds when crossing only XX plants (Green, 2005). Furthermore, a significant improvement of tCBD/tTHC ratio was observed (with a maximal tCBD content of 29.58% measured in a plant with a tTHC as low as 0.82%) after crossing only 23 selected parental plants. It shows that crossing plants selected based on their chemotype profile improves the genetic constitution of the breeding population and consequently enables the development of new varieties with improved cannabinoid profiles.

These mother plants were cloned, induced to produce male flowers by spraying them with 30 ppm colloidal silver every day, and left to cross-pollinate in a contained flowering chamber. The colloidal silver treatment was chosen based on our results obtained in the above described experiments, which demonstrated the best performance in terms of the number of in vitro germinated pollen grains and of the number of developing seeds ( Tables 5 , ​ ,6). 6 ). Seeds were left on plants until maturity when they were sown, and a 64.3% germination rate was recorded. The cannabinoid analysis of 74 seedlings showed that their flowers contained from 1.77 to 24.34% and 0.09 to 0.85% of tCBD and tTHC, respectively. The ratio between tCBD and tTHC varied between 13.26 and 29.58 ( Figure 3 ).

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The aim of our investigation was to test different sex manipulation methods (chemical, hormonal, and physiological) for induction of male flowers on female plants of medical cannabis and to evaluate their efficiency based on the number of male inflorescences and male flowers, by evaluation of pollen viability, germination potential in vitro and in vivo, and seed set. In addition, the selected treatment was implemented in a breeding program for crossing a population of female plants of a high CBD breeding population of medical cannabis to verify the usefulness of such treatments in the high-valued medical cannabis industry.

Distribution of the ratios between tCBD and tTHC in 48 mother plants of breeding population MX-CBD-707 (left-blue) and 74 of their progeny (right-green).

Author Contributions

The germination ability of pollen was confirmed also with in vivo pollination of female flowers. After 24 h, the germinating pollen tubes were clearly visible on stigmas stained with aniline blue ( Figure 1D ).

Treatments of the first experiment of male flowers induction on female plants of Cannabis sativa.

A number of nodes per plant, both expressed as a ratio between the final state (measurement/count at the end of the experiment) and the initial state (counted at the start of the experiment prior to (pre)treatments). In this way, not only the final morphology of the plants was taken into account, but also the initial state of the plants.


In the second experiment ( Table 2 ), 45 plants of breeding population MX-CBD-707 were treated for male sex induction. After 60 days on vegetative growth, they were first exposed to three different lighting regimes (henceforth referred to as “pretreatments;” 15 plants per pretreatment), which was followed by four different treatments: spraying whole plants with STS (Green, 2005), spraying whole plants with colloidal silver once, or every day until anthesis (recommendation of grower), and control (non-treated plants).

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The number of inflorescences with one male flower or more per plant.