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A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives.

ABSTRACT: Two kinds of drug-type Cannabis gained layman's terms in the 1980s. "Sativa" had origins in South Asia (India), with early historical dissemination to Southeast Asia, Africa, and the Americas. "Indica" had origins in Central Asia (Afghanistan, Pakistan, Turkestan). We have assigned unambiguous taxonomic names to these varieties, after examining morphological characters in 1100 herbarium specimens, and analyzing phytochemical and genetic data from the literature in a meta-analysis. "Sativa" and "Indica" are recognized as C. sativa subsp. indica var. indica and C. sativa subsp. indica var. afghanica, respectively. Their wild-growing relatives are C. sativa subsp. indica var. himalayensis (in South Asia), and C. sativa subsp. indica var. asperrima (in Central Asia). Natural selection initiated divergence, driven by climatic conditions in South and Central Asia. Subsequent domestication drove further phytochemical divergence. South and Central Asian domesticates can be distinguished by tetrahydrocannabinol and cannabidiol content (THC/CBD ratios, ?7 or <7, respectively), terpenoid profiles (absence or presence of sesquiterpene alcohols), and a suite of morphological characters. The two domesticates have undergone widespread introgressive hybridization in the past 50 years. This has obliterated differences between hybridized "Sativa" and "Indica" currently available. "Strains" alleged to represent "Sativa" and "Indica" are usually based on THC/CBD ratios of plants with undocumented hybrid backgrounds (with so-called "Indicas" often delimited simply on possession of more CBD than "Sativas"). The classification presented here circumscribes and names four taxa of Cannabis that represent critically endangered reservoirs of germplasm from which modern cannabinoid strains originated, and which are in urgent need of conservation.

SUBMITTER: McPartland JM

PROVIDER: S-EPMC7148385 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives.

McPartland John M JM Small Ernest E

PhytoKeys 20200403

Two kinds of drug-type <i>Cannabis</i> gained layman's terms in the 1980s. "Sativa" had origins in South Asia (India), with early historical dissemination to Southeast Asia, Africa, and the Americas. "Indica" had origins in Central Asia (Afghanistan, Pakistan, Turkestan). We have assigned unambiguous taxonomic names to these varieties, after examining morphological characters in 1100 herbarium specimens, and analyzing phytochemical and genetic data from the literature in a meta-analysis. "Sativa ...[more]

PMID: 32296283

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Project description:BackgroundGlandular capitate trichomes which form on bract tissues of female inflorescences of high THC-containing Cannabis sativa L. plants are important sources of terpenes and cannabinoids. The influence of plant age and cannabis genotype on capitate trichome development, morphology, and maturation has not been extensively studied. Knowledge of the various developmental changes that occur in trichomes over time and the influence of genotype and plant age on distribution, numbers, and morphological features should lead to a better understanding of cannabis quality and consistency.MethodsBract tissues of two genotypes-"Moby Dick" and "Space Queen"-were examined from 3 weeks to 8 weeks of flower development using light and scanning electron microscopy. Numbers of capitate trichomes on upper and lower bract surfaces were recorded at different positions within the inflorescence. Observations on distribution, extent of stalk formation, glandular head diameter, production of resin, and extent of dehiscence and senescence were made at various time points. The effects of post-harvesting handling and drying on trichome morphology were examined in an additional five genotypes.ResultsTwo glandular trichome types-bulbous and capitate (sessile or stalked)-were observed. Capitate trichome numbers and stalk length were significantly (P = 0.05) greater in "Space Queen" compared to "Moby Dick" at 3 and 6 weeks of flower development. Significantly more stalked-capitate trichomes were present on lower compared to upper bract surfaces at 6 weeks in both genotypes, while sessile-capitate trichomes predominated at 3 weeks. Epidermal and hypodermal cells elongated to different extents during stalk formation, producing significant variation in length (from 20 to 1100 μm). Glandular heads ranged from 40 to 110 μm in diameter. Maturation of stalked-capitate glandular heads was accompanied by a brown color development, reduced UV autofluorescence, and head senescence and dehiscence. Secreted resinous material from glandular heads appeared as droplets on the cuticular surface that caused many heads to stick together or collapse. Trichome morphology was affected by the drying process.ConclusionCapitate trichome numbers, development, and degree of maturation were influenced by cannabis genotype and plant age. The observations of trichome development indicate that asynchronous formation leads to different stages of trichome maturity on bracts. Trichome stalk lengths also varied between the two genotypes selected for study as well as over time. The variability in developmental stage and maturation between genotypes can potentially lead to variation in total cannabinoid levels in final product. Post-harvest handling and drying were shown to affect trichome morphology.

Dataset Information

A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives.

Publications

A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives.

Similar Datasets

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