to allow cultivation of hemp varieties with a ⌬ 9 -THC content below 0.3%. By 1998 hemp was reintroducedThe objective was to study the genetic structure and degree of in practically all of Europe (Bó csa and Karus, 1998), variability of hemp (Cannabis sativa L.) varieties. Six varieties of hemp were analyzed by random amplified polymorphic DNA though in some countries significant resources are still (RAPD) analysis, using 10 plants per variety. The varieties were a being employed to prevent hemp diffusion regardless dioecious landrace, a dioecious selection from it, a cross-bred cultivar, of its ⌬ 9 -THC content (Linacre and Thorpe, 1998). a monoecious variety, a drug strain, and an inbred female line. The Because of the continuous variation of most morphogenetic complexity of each cultivar was investigated by determining logical and biochemical traits within the Cannabis genus, the number of bands produced by the primers used, the number of it would be useful to identify groups on the basis of fixed and polymorphic loci, the average allele frequency, and the their use or origin. A nonbiosystematic classification heterozygosity. A good correlation was found between these paramedistinguishes wild populations from fiber landraces, culters and the genetic origin and breeding strategy of each variety. The tivars, drug strains, and ornamentals (de Meijer, 1995). average polymorphism over all varieties and loci was 97.1%; the single Hemp cultivars are characterized by different degrees cultivar polymorphism ranged from 31.1 to 85.5%. Heterozygosity ranged from 0.05 (inbred female line) to 0.26 (cross-bred Fibranova). of genetic variability because of commercial value, re-The average heterozygosity calculated over all 102 loci and all plants productive biology (dioecious or monoecious), end use, studied was 0.29. The Fst (Wright's fixation index) value calculated and different criteria employed in breeding. for all loci was 0.48, and only 33.3% of the scored loci had higher Dioecious cultivars (e.g., Italian fiber varieties) are values and can be considered informative for cultivar identification. obligate outbred, and the method used to multiply them A Fisher's test based on allele frequencies suggested complete differ-(open-field pollination) approaches a random-mating entiation among all varieties, with the exception of the Italian dioecondition. This is also true for monoecious cultivars, cious varieties Carmagnola and CS, for which no discriminating alleles which are composed of about 50 to 70% monoecious were found. The correlations among the molecular data and the geplants and 30 to 50% female plants, with a small number netic structure of the different cultivars and the consequences in of male plants. The original monoecious trait occurred relation to variety discrimination in hemp are discussed.spontaneously in material from central Russia (de Meijer, 1995) and the presence of male plants in a monoecious stand must be limited to avoid reversion to the Istituto Sperimentale per le Colture Industriali, Via di C...
