Potential of marker-assisted selection in hemp genetic improvement

Abstract

The development and applications of molecular markers to hemp breeding are recent, dating back only to the mid1990s. The main achievements in this field are reviewed. The analysis of Cannabis germplasm by RAPD, AFLP and microsatellites is discussed, with its consequence for the still debated species concept in Cannabis. DNA-based markers have also been exploited in the field of forensic science, in an attempt to discriminate licit from illicit crop. The main applications of the molecular markers to the breeding, however, have been achieved with the development of markers closely linked to the male sex and to some of the most relevant chemotypes. Active research is carried out by several groups in the field of identification and characterization of the genes involved in fiber quality and quantity, and in the determination of monoecy, another very important target of hemp breeding. Besides, markers associated to new, potentially useful chemotypes are being developed, for the marker-assisted breeding of pharmaceutical Cannabis.

Time course of cannabinoid accumulation and chemotype development during the growth of Cannabis sativa L

“…No plants of chemotype V (zero cannabinoids; Mandolino and Carboni 2004) were detected within these three accessions, in agreement with previously published results (PaciWco et al 2006).…”

“…Chemotype II, the intermediate type, has both CBD and THC, in a ratio around the unity (typically 0.5-2.0); chemotype III, the "Wbre" type, has mainly CBD, and a level of THC lower than 0.30% (down to undetectability). Later, two other chemotypes were deWned: chemotype IV has a prevalence of CBG (>0.30%), but also CBD (<0.50%; Fournier et al 1987); and chemotype V, with amounts of all cannabinoids practically undetectable by standard gas-chromatographic analysis (Mandolino and Carboni 2004).…”

Classification of Cannabis Cultivars Marketed in Canada for Medical Purposes by Quantification of Cannabinoids and Terpenes Using HPLC-DAD and GC-MS

“…The first, a botanical perspective, attempts to classify cannabis into different species or subspecies based on appearance, THC content, and geographical origins (gene pools) [8][9][10][11][12][13]. The second, a chemotaxonomic perspective, describes five chemotypes (chemical phenotypes) based on the ratio of two major cannabinoids THC and CBD, which is decided by their corresponding allelic loci [14][15][16][17][18][19][20][21]. Recently, a third perspective seeks to categorize cultivars based on both cannabinoids and terpenes for drug standardization and clinical research purposes [22,23].…”

Characterisation of cannabinoid composition in a diverse Cannabis sativa L. germplasm collection

“…CBGVA (CBG(V)A) accumulation and chemotype IV; cannabidiolic acid (CBDA); cannabidivarinic acid (CBDVA); cannabigerolic acid (CBGA); cannabigerovarinic acid (CBGVA); delta-9-tetrahydrocannabinolic acid (THCA); delta-9-tetrahydrocannabivarinic acid (THCVA) indeed for eliminating psychoactive constituents from industrial hemp (Mandolino and Carboni 2004). Genetic metabolic engineering through exploitation of natural occurring allelic and chemotypic diversity within the gene pool (Barker et al 2007), and subsequent generation of novel recombined breeding lines using marker assisted selection (Mandolino and Carboni 2004;Potter 2014), may lead to the development of standardised multi-targeting botanical drug products from a single plant line. Rigorous characterisation of chemotype may also aid in the development of fibre hemp and seed cultivars which can maintain levels of THC within legal regulatory thresholds of 0.2 % dry weight (w/w) (DW) (Kojoma et al 2006;Mandolino and Carboni 2004;Pacifico et al 2006).…”