In previous reviews (Mandolino and Carboni 2004 ; Mandolino 2007 ), the
exploitation of genomic tools has been described, considering three issues of
research: the description of the genetic structure ofCannabisthrough molecular
markers; the identification of the sexual phenotype; and the study of the
chemotype-determining factors. Ten years later,Cannabisproducts also entered the
food and cosmetic industries, the automotive and green building industries, but the
previously described issues can also be considered of primary significance for the
new uses ofCannabis. Extensive knowledge of theCannabisgenome and the
development of molecular markers have been made possible by the significant
contribution of forensic studies. Therefore, we will begin this review by discussing
some of the issues that geneticists share with forensic scientists, also endeavoring to
derive from them information that might be useful to breeders.
15.2 Molecular Markers for the Study of Variability
and Genetic Structure ofCannabis sativa
15.2.1 Early Molecular Markers (RAPDs, RFLPs, AFLPs,
Microsatellites (SSRs), ISSRs): The Forensic Issue
and Estimates of Genetic Variability in CannabisHistorically, a great propulsion in the development of specific molecular markers
forCannabis sativahas been provided by the necessity of forensic scientists to
develop, for their tasks, tools that can either identify unambiguouslyCannabis-
containing materials, or differentiate so-called“fiber-type”from“drug-type”plants.
Moreover, tracing the geographic diffusion routes of theCannabisdrug strains has
also been an important issue for law enforcement agencies. Different approaches,
involving the use of different progressively available molecular markers, have been
selected over the years to address these issues.
In early research, organelle genomes have been used as sources of sequences
useful to forensic discrimination of different plant materials. In fact, a
well-conserved short intergenic sequence of chloroplast DNA (ctDNA) with very
low nucleotide polymorphism, located between the tRNA genes trnL and trnF, was
soon identified as a specific marker for recognizingCannabisDNA (Linacre and
Thorpe 1998 ; Wilkinson and Linacre 2000 ). These research lines are still very
active, as recently, a 687 bp-consensus sequence has been identified from the same
intergenic region (Dias et al. 2015 ), which discriminatesCannabisDNA from other
members of theCannabaceaefamily, and shows the same power of discrimination
possessed by other longer fragments normally considered more reliable in mini-
mizing stochastic variation across taxa. The complete sequencing of theCannabis
chloroplast genome, recently accomplished (Oh et al. 2015 ; Vergara et al. 2015 ),
opens the way to a more extensive exploitation of the chloroplast genome as a
possible source of markers, especially for phylogenetic studies.
320 C. Onofri and G. Mandolino