Cannabis sativa is a diploid, dioecious species and is commonly referred to as hemp or marijuana, depending on the amount of tetrahydrocannabinol (THC) produced by the plant. Female plants are preferred for the production of cannabinoids, such as THC and CBD, because they produce significantly more cannabinoids than male plants. Feminized seed is desirable for CBD hemp production. Feminized seed is produced when female plants are pollinated using pollen from masculinized female plants (Mohan Ram and Sett, 1982). Masculinization of female plants can be accomplished using foliar sprays of silver thiosulfate (Lubell and Brand, 2018). Based on statements from hemp growers and extension educators, seed producers may implement selfing (crossing a single genotype with itself) to generate feminized seed. When producing feminized seed, growers will vegetatively propagate a selected female genotype, and masculinize some percentage of the potted clones to generate female pollen, which is then used to pollinate the remaining nonmasculinized clones. The seed resulting from this self-cross is referred to as the S1 or first self-generation (MH International, 2020). It is possible that producers are unintentionally generating feminized seed by selfing that is beyond the S1 to the S2 and S3 generations, which may exhibit inbreeding depression.
Currently there are no guidelines, regulations, or requirements for the genetics of feminized seed. Therefore, the origin of seeds in the marketplace is typically unknown or unsubstantiated with breeding pedigrees. For example, it is unknown whether feminized seed of cultivar A is produced using two parents of an identical genotype or two parents of related genotypes. Furthermore, when cultivar nomenclature is applied to hemp, it is generally unknown whether the cultivar is a single clonally propagated genotype, stabilized inbred seed, or seed produced by hybridization within a family of related genotypes. The objective of this research was to evaluate the phenotypic and genotypic diversity of selfed and outcrossed feminized seed progeny for CBD production purposes.
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