So far the differentiation between illegally grown drug strains and fibre hemp cultivars of Cannabis (hemp) is based on a time-consuming chemical analysis which cannot be applied to all plant materials.
In Europe, around 50 officially approved fibre hemp cultivars of Cannabis (hemp) are grown for agricultural production and should contain < 0,2% tetrahydrocannabinol (THC), a psychoactive cannabinoid. Next to this, numerous drug strains with a THC content up to >20% are grown illegally. So far, a differentiation of these two groups relies on a timeconsuming quantitative biochemical assessment of cannabinoids in flowering plant material. Quite often non-flowering plants (e.g. in 2014 about 30 times in Niederösterreich) or plant material which does not contain cannabinoids (e.g. roots or seeds; in 2014 more than 50 samples in Niederösterreich) – found in very young or already harvested indoor plantations, in seized seed packs or in escapes growing outdoor - cannot be classified at all and is therefore lost for further investigations - or has to be grown extensively in glass houses until flowering.
The genetic determination of the so-called chemotype, a category superior to a cultivar, could be used for a more efficient forensic differentiation depending on the survey described. The genetic analysis is faster and cheaper than the biochemical assessment and can be applied to all plant materials without further growing - even if the material does not contain THC, such as roots or seeds. The BKA stresses the need for this additional DNA method (marker system D589; Staginnus et al., 2014) in forensic applications. It could be available at the AGES for future forensic casework.
Depending on the relative ratio of the cannabinoids THC and Cannabidiol (CBD), a nonpsychoactive component, in mature inflorescences three discrete chemical chemotypes can be distinguished: a “THC-predominat” type, a “CBD-predominant” type and an intermediate chemotype. Chemotypes are qualitative traits, their use for certain cultivars or strains is manmade and depends on the breeder. They are not necessarily linked to the absolute THC yield. However, the breeding aim of a comparatively high THC yield commonly used for drug strains is more easily achieved by using the “THC-predominant” or the intermediate type whereas the “CBD-predominat” chemotype facilitates conformation with the limit of 0.2% THC for fibre hemp. However the actual use of the “CBD-predominant” chemotype for breeding European fibre hemp has not been investigated systematically so far. The genetic determination of the chemotype can only be applied for the forensic differentiation of drug strains and fibre hemp cultivars if European fibre hemp cultivars would prove to consist mainly or entirely of the “CBD-predominant” chemotype and the latter could be used as a characteristic trait for classification.
In the planned survey the chemotypes of all European fibre hemp cultivars will therefore be determined by systematic sampling and analysis with the genetic marker system D589. Results will be collected in a database which is accessible for all forensic users and breeders. Both, a reference collection of all hemp cultivars analyzed and the establishment of the genetic chemotype
Dipl.-Ing. Verena Peterseil
AGES (Österreichische Agentur für Gesundheit und Ernährungssicherheit)
Institut für Lebensmittelsicherheit Wien
Spargelfeldstraße 191, 1220 Wien