A Belated Green Revolution for Cannabis: Virtual Genetic Resources to Fast-Track Cultivar Development

Abstract

Cannabis is a predominantly diecious phenotypically diverse domesticated genus with few if any extant natural populations. International narcotics conventions and associated legislation have constrained the establishment, characterization, and use of Cannabis genetic resource collections. This has resulted in the underutilization of genepool variability in cultivar development and has limited the inclusion of secondary genepools associated with genetic improvement strategies of the Green Revolution. The structured screening of ex situ germplasm and the exploitation of locally-adapted intraspecific traits is expected to facilitate the genetic improvement of Cannabis. However, limited attempts have been made to establish the full extent of genetic resources available for pre-breeding. We present a thorough critical review of Cannabis ex situ genetic resources, and discuss recommendations for conservation, pre-breeding characterization, and genetic analysis that will underpin future cultivar development. We consider East Asian germplasm to be a priority for conservation based on the prolonged historical cultivation of Cannabis in this region over a range of latitudes, along with the apparent high levels of genetic diversity and relatively low representation in published genetic resource collections. Seed cryopreservation could improve conservation by reducing hybridization and genetic drift that may occur during Cannabis germplasm regeneration. Given the unique legal status of Cannabis, we propose the establishment of a global virtual core collection based on the collation of consistent and comprehensive provenance meta-data and the adoption of high-throughput DNA sequencing technologies. This would enable representative core collections to be used for systematic phenotyping, and so underpin breeding strategies for the genetic improvement of Cannabis.

Broad-Scale Genetic Diversity of Cannabis for Forensic Applications

“…This crop was since distributed across the world during the last two millennia and, due to its recent legalization in several countries, is increasingly exploited by several industrial sectors (hemp) and as a recreational drug (marijuana). The taxonomic status of Cannabis has always been disputed, as it encompasses multiple cultural, geographic, historical and functional aspects (reviewed in [1–4]). Whereas most authors now consider it a monotypic panmictic taxon, Cannabis sativa , three species or subspecies ( sativa , indica and ruderalis ) are often mentioned but without a comprehensive taxonomic grouping so far.…”

“…Whereas most authors now consider it a monotypic panmictic taxon, Cannabis sativa , three species or subspecies ( sativa , indica and ruderalis ) are often mentioned but without a comprehensive taxonomic grouping so far. The nomenclature may thus differ depending on whether it refers to morphological or chemical variation, geographic distribution, ecotype, as well as crop-use characteristics and intoxicant properties resulting from human selection [4–7]. Cannabis presumably diversified following selection for traits enhancing fibre and seed production (”hemp”) or psychoactive properties ("drug").…”

Developing Robust Standardised Analytical Procedures for Cannabinoid Quantification: Laying the Foundations for an Emerging Cannabis-Based Pharmaceutical Industry

“…Production and quality control of Cannabis -based biological medicines derived from recombinant DNA technology are also subject to market authorisation guidelines (e.g., EMA European Guidelines 3AB1a), which require product purification to remove protein and nucleic acid contaminants derived from the host cell. Given the obligate outcrossing nature of Cannabis [34] as well as heterozygosity within the gene pool [3, 35], seed-grown Cannabis botanical raw material can be highly variable in content and composition of target and non-target active ingredients [31, 36]. Thus, clonal propagation using callus- [37] or nodal- (axillary buds) [38] mediated regeneration is favoured over seed propagation [22], with explants typically grown under environmentally controlled conditions in an effort to minimise genetic by environment interactions and to maximise product uniformity [31].…”

“…Cannabis is a chemically complex [1], pharmaceutically relevant [2], domesticated [3], monospecific genus within the angiosperm family Cannabaceae, order Rosales [4]. Plants of this genus produce a group of isoprenylated resorcinyl polyketides, also known as cannabinoids [5].…”

“…This is primarily due to a lack of high-quality clinical evidence supporting medical use [2], a situation exacerbated by legislative constraints associated with the United Nations 1961 Single Convention on Narcotic Drugs and the 1971 Convention of Psychotropic Substances, which have severely restricted research into Cannabis pharmacology and therapeutic use [3, 12]. These constraints have also inhibited clinicians from exploring therapeutic value and severely limited patient access in most legislatures, with clinical application further blocked by the removal of Cannabis from pharmacopoeias in the 1970s [13, 14].…”