The origin of the genus Cannabis

Abstract

Chloroplast markers (cp markers) are the useful instrument for cannabis (syn. hemp, Cannabis sativa L.) to study relationships of accessions between different geographic origins. In an alignment of three published plastomes 38 chloroplast polymorphisms were identified from which 8 cp markers were used to study relationships of 53 cannabis accessions by high-resolution-melting analyis (HRMA). The marker set could distinguish six haplotypes (‘A’ to ‘F’) in the cannabis collection, where haplotypes ‘A’ and ‘F’ dominated with 34% and 50% of the individuals, respectively. A majority of populations (37) were homogeneous regarding the haplotype, 12 accessions were constituted of two haplotypes and 4 accessions of three haplotypes. Most of the European fibre cultivars consisted of the ‘F’-type (e.g. ‘Fibrimon’, Fibrimon 21’, Juso 14’, ‘Fasamo’ and ‘Schurig’), some were mixed ‘A/F’-types (e.g. ‘Fibrimon 21’, ‘Superfibra’, ‘Lorrin 110’, ‘Futura’, ‘Havelländische’). The Italian ‘Carmagnola in Selezione’ was exceptional in being a pure ‘A’-type. In the heterogenous populations, expected heterozygosity ranged from 0.06 to 0.41. The populations were well differentiated by this marker set locating 79% of the variation among populations (AMOVA). By comparison with plastomes from the closest related genus Humulus, haplotype ‘B’ could be identified as haplotype of the common ancestor of both genera. The haplotype ‘B’ is rare with a frequency of only 4% in the populations analysed. Unfortunately, the true geographic origin of most samples was unclear. However, amongst all published plastomes, only two were classified as haplotype ‘B’, both pointing independently back to Yunnan province (China), indicating Yunnan as the region of origin of the genus Cannabis.