A PCR marker Linked to a THCA synthase Polymorphism is a Reliable Tool to Discriminate Potentially THC-Rich Plants of Cannabis sativa L.

Neither absolute THC content nor morphology allows the unequivocal discrimination of fiber cultivars and drug strains of Cannabis sativa L. unequivocally. However, the CBD/THC ratio remains constant throughout the plant's life cycle, is independent of environmental factors, and considered to be controlled by a single locus (B) with two codominant alleles (BT and BD). The homozygous BT/BT genotype underlies the THC-predominant phenotype, BD/BD is CBD predominant, and an intermediate phenotype is induced by the heterozygous state (BT/BD). Using PCR-based markers in two segregating populations, we proved that the THCA synthase gene represents the postulated B locus and that specific sequence polymorphisms are absolutely linked either to the THC-predominant or the THC-intermediate chemotype. The absolute linkage provides an excellent reliability of the marker signal in forensic casework. For validation, the species-specific marker system was applied to a large number of casework samples and fiber hemp cultivars.