Germplasm
More actions
Germplasm is the genetic material that forms the physical basis of heredity and passes from one generation to the next through the germ cells.[1]: 164 Gene banks keep plant germplasm as seed, as live plants in field collections and as plant organs grown on a nutrient medium. Buds, shoot tips, embryos and pollen can also be frozen in liquid nitrogen.[1]: 162–164 The International Treaty on Plant Genetic Resources for Food and Agriculture uses the term "genetic material" for "any material of plant origin, including reproductive and vegetative propagating material, containing functional units of heredity".[2]: 3
A review published in 2016 found that the international drug conventions and the laws that go with them had held back the founding, description and use of Cannabis collections. Collections in North America were confiscated late in the 20th century. Some were reportedly destroyed.[3] The plant is dioecious and pollinated by wind, so accessions regrown near one another cross unless they are kept apart.[3] In 2020 John M. McPartland and Ernest Small described the drug-type domesticates of Central and South Asia and their wild relatives as "critically endangered reservoirs of germplasm from which modern cannabinoid strains originated". They called the collection and conservation of the landraces' germplasm in their centres of diversity urgent.[4]
Samples and their documents
A gene bank holds germplasm as accessions. Each is "a distinct, uniquely identifiable sample of seeds representing a cultivar, breeding line or a population, which is maintained in storage for conservation and use".[1]: 162 Its passport data give its origin: the details taken down where it was collected, its pedigree and anything else that identifies it.[1]: 165 A landrace, in the glossary of the same standards, is a crop cultivar shaped over many years by farmers' selection and adapted to local conditions, and it is usually genetically mixed.[1]: 164
Public passport data for cannabis are missing or of low quality. In the 2016 review, the former Centre for Plant Breeding and Reproduction Research (CPRO) at Wageningen was the one published collection to give passport data for each accession. The reports on the Vavilov Institute collection and on that of the Institute of Natural Fibres and Medicinal Plants in Poland listed only the number of accessions from each country. In the reviewers' view this left cannabis without the mapping methods other crops use to choose where to collect next.[3]
The United States Department of Agriculture received PI 5021, cannabis seed from Shanghai, on 28 March 1900. The accession "no longer exists and can not be requested", and the database of the National Plant Germplasm System keeps its entry as historical information.[5]
Forms of storage
Seed
Seeds that can be dried to a low moisture content and stored cold without harm are called orthodox.[1]: 165 Long-term storage keeps them below freezing, and the period before a sample must be regrown is at least several decades and possibly a century or more.[1]: 164 Cannabis seed appears to be orthodox: it has stood up to 66 months after drying with little loss of viability. Common practice is to store it at 4 °C and 6 per cent moisture for short periods, and at −20 °C and about 4 per cent for more than three years. Welling and colleagues found no systematic evidence of how long it stays viable in store.[3]
Regrowing
Regeneration is the growing out of a seed accession to obtain a fresh sample with high viability and many seeds.[1]: 165 For cannabis it is costly. Male and hermaphrodite plants shed large amounts of pollen, so gene flow between accessions has to be prevented. Accessions from different latitudes need different day lengths to begin flowering, which confines outdoor regrowing to certain times of year. Indoor rooms built to keep pollen in hold few plants, and with few parents an accession may lose some of its alleles at each cycle.[3] Welling and colleagues suggested that freezing the seed could reduce the crossing and genetic drift that regrowing brings.[3]
Plants, tissue and pollen
Other germplasm is kept as live plants in field gene banks, as plant organs grown on an artificial nutrient medium in glass or plastic containers, and frozen in liquid nitrogen at −196 °C or in its vapour at −140 °C or below. Frozen storage serves for buds, shoot tips, embryos and pollen. A stored pollen sample yields plants only through a cross, so a living plant must be at hand to receive it.[1]: 162–164
In 2019 Esther Uchendu and colleagues froze shoot tips cut from shoots of three cannabis cultivars grown in culture: one high in THC, one high in CBD and one intermediate. With the best of the three treatments, 63 per cent of the high-THC tips and 57 per cent of the high-CBD tips grew again after thawing. The authors called it the first report of a method for freezing organised cannabis tissue for germplasm conservation.[6]
Collections
The Vavilov Institute in Saint Petersburg, formerly the All-Union Institute of Plant Industry, was founded by Nikolai Vavilov in 1920. In 1998 its collection held nearly 500 cannabis accessions of known origin, 61.3 per cent of them from Ukraine, Russia and Germany.[3][7]
The CPRO collection at Wageningen was founded in 1988. It held 156 accessions from more than 22 countries. Cultivars of mostly European origin and drug-type varieties made up over 40 per cent of them.[3]
The Leibniz Institute of Plant Genetics and Crop Plant Research at Gatersleben holds CAN 20, a landrace collected in North Korea on 12 November 1985 during its mission PRK-85.[8] In May 2023 the institute gave the National Plant Germplasm System its CAN 22, seed of Cannabis sativa subsp. spontanea collected before 1987 near a cattle enclosure in Khevsureti, Georgia, which the system holds as G 33598.[9][10]
In 2015 the Polish collection at Poznań held 139 accessions, most of them European. The Yunnan Academy of Agricultural Sciences in Yunnan held about 350, mostly East Asian. The company Ecofibre held a collection from many parts of Eurasia in Australia. Of 808 accessions reported from collections worldwide, 58 came from China.[3]
Since 2021 the Plant Genetic Resources Unit at Geneva, New York has gathered a hemp collection of more than 600 accessions from 35 countries.[11] Among its accessions is G 33685, a landrace from fields on the outskirts of Balkh in Afghanistan, which arrived as one seed packet on 22 August 2023. Its entry reads "This accession is not available."[12]
Access under drug-control law
The Single Convention on Narcotic Drugs of 1961 defines cannabis as the flowering or fruiting tops of the plant and leaves the seeds out of the definition. It does not apply to cultivation solely for fibre, seed or horticulture.[13]: arts. 1, 28 Welling and colleagues still named the limits on the import, export and transfer of seed between parties to the 1961 convention and the Convention on Psychotropic Substances of 1971 as one barrier to a shared physical collection of cannabis. The other was the lack of seed banks open to the public. They proposed instead a "virtual" core collection of up to 400 accessions, kept in the existing gene banks and described in one shared database of passport and trait data.[3]
Under the United States' 2018 Farm Bill, hemp is cannabis with no more than 0.3 per cent delta-9 THC by dry weight, and it is no longer a controlled substance under federal law.[11]
The plant treaty's multilateral system covers the crops listed in its Annex I, and cannabis is not among them.[2]: 46–49
Landrace germplasm
Crop wild relatives, local landraces and other germplasm that has seen little domestication hold alleles that breeding can bring back into domesticated lines.[3] Welling and colleagues named East Asian cannabis a priority for collecting, for its long cultivation across many latitudes, its high genetic diversity and its thin presence in the collections.[3]
Breeders crossed Central Asian and South Asian drug-type landraces without plan and largely erased the differences between them. By the mid-1980s unhybridised landraces were hard to obtain in the United States and Europe.[4] McPartland and Small found that foreign germplasm had since reached the landraces' own centres of diversity and that they face extinction through introgressive hybridisation. They judged conservation in the field better for crops and their wild relatives, but called seed banks "an immediate priority" for cannabis, given the precarious state of its wild populations in Asia.[4]
In Morocco, broad-leaflet genetics from Central Asia were brought into the local crop in 1980. In the account of Bachir and colleagues the local narrow-leaflet landrace, kif, is now rare and faces extinction through introgressive hybridisation.[14] The loss of a landrace's own make-up through crossing is treated under genetic contamination.
See also
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Food and Agriculture Organization of the United Nations (2014). Genebank Standards for Plant Genetic Resources for Food and Agriculture (PDF) (Revised ed.). Rome: FAO. ISBN 978-92-5-108262-1.
- ↑ 2.0 2.1 Food and Agriculture Organization of the United Nations. International Treaty on Plant Genetic Resources for Food and Agriculture (PDF). Rome: FAO.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 Welling, M.T.; Shapter, T.; Rose, T.J.; Liu, L.; Stanger, R.; King, G.J. (2016). "A belated green revolution for Cannabis: virtual genetic resources to fast-track cultivar development". Frontiers in Plant Science. 7 1113. doi:10.3389/fpls.2016.01113.
- ↑ 4.0 4.1 4.2 McPartland, J.M.; Small, E. (2020). "A classification of endangered high-THC cannabis (Cannabis sativa subsp. indica) domesticates and their wild relatives". PhytoKeys. 144: 81–112. doi:10.3897/phytokeys.144.46700.
- ↑ "PI 5021, Cannabis sativa L." GRIN-Global. United States Department of Agriculture, Agricultural Research Service. Retrieved 27 October 2026.
- ↑ Uchendu, E.; Lata, H.; Chandra, S.; Khan, I.A.; ElSohly, M.A. (2019). "Cryopreservation of shoot tips of elite cultivars of Cannabis sativa L. by droplet vitrification". Medical Cannabis and Cannabinoids. 2 (1): 29–34. doi:10.1159/000496869.
- ↑ Clarke, R.C. (1998). "Maintenance of Cannabis germplasm in the Vavilov Research Institute Gene Bank: five year report". Journal of the International Hemp Association. 5 (2): 75–79.
- ↑ "CAN 20, Cannabis sativa L." Genesys. Global Crop Diversity Trust. Retrieved 12 October 2026.
- ↑ "Occurrence 120968587: Cannabis sativa subsp. spontanea (Czern.) Serebr. ex Serebr. & Sizova". GBIF. Global Biodiversity Information Facility. Retrieved 14 October 2026.
- ↑ "G 33598, Cannabis sativa subsp. spontanea". GRIN-Global. USDA Agricultural Research Service, National Plant Germplasm System. Retrieved 14 October 2026.
- ↑ 11.0 11.1 Stansell, Zachary; Gordon, Tyler. "Hemp Collection". Plant Genetic Resources Unit, Geneva, New York. USDA Agricultural Research Service. Retrieved 14 October 2026.
- ↑ "G 33685, Cannabis sativa L., Balkh ('Green / Purple')". GRIN-Global. USDA Agricultural Research Service, National Plant Germplasm System. Retrieved 27 October 2026.
- ↑ "Single Convention on Narcotic Drugs, 1961, as amended by the 1972 Protocol amending the Single Convention on Narcotic Drugs, 1961" (PDF). United Nations. Retrieved 30 September 2026 – via United Nations Office on Drugs and Crime.
- ↑ Bachir, Fatima; Eddouks, Mohamed; Arahou, Mohamed; Fekhaoui, Mohammed (2022). "Origin, Early History, Cultivation, and Characteristics of the Traditional Varieties of Moroccan Cannabis sativa L.". Cannabis and Cannabinoid Research. 7 (5): 603–615. doi:10.1089/can.2021.0020.