title: Evaluation of a 13-loci STR multiplex system for Cannabis sativa genetic identification.
abstract: Marijuana (Cannabis sativa) is the most commonly used illicit substance in the USA. The development of a validated method using Cannabis short tandem repeats (STRs) could aid in the individualization of samples as well as serve as an intelligence tool to link multiple cases. For this purpose, a modified 13-loci STR multiplex method was optimized and evaluated according to ISFG and SWGDAM guidelines. A real-time PCR quantification method for C. sativa was developed and validated, and a sequenced allelic ladder was also designed to accurately genotype 199 C. sativa samples from 11 U.S. Customs and Border Protection seizures. Distinguishable DNA profiles were generated from 127 samples that yielded full STR profiles. Four duplicate genotypes within seizures were found. The combined power of discrimination of this multilocus system is 1 in 70 million. The sensitivity of the multiplex STR system is 0.25 ng of template DNA. None of the 13 STR markers cross-reacted with any of the studied species, except for Humulus lupulus (hops) which generated unspecific peaks. Phylogenetic analysis and case-to-case pairwise comparison of 11 cases using F st as genetic distance revealed the genetic association of four groups of cases. Moreover, due to their genetic similarity, a subset of samples (N = 97) was found to form a homogeneous population in Hardy-Weinberg and linkage equilibrium. The results of this research demonstrate the applicability of this 13-loci STR system in associating Cannabis cases for intelligence purposes.
authors.affiliation: Department of Forensic Science, College of Criminal Justice, Sam Houston State University, 1003 Bowers Blvd., Huntsville, TX, 77340-2525, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Houston
authors.affiliation: New York Laboratory, U.S. Customs and Border Protection, U.S. Department of Homeland Security, 1100 Raymond Blvd, Newark, NJ, 07102, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Birck
authors.affiliation: Department of Forensic Science, College of Criminal Justice, Sam Houston State University, 1003 Bowers Blvd., Huntsville, TX, 77340-2525, USA.
authors.forename: Sheree
authors.initials: S
authors.lastname: Hughes-Stamm
authors.affiliation: Department of Forensic Science, College of Criminal Justice, Sam Houston State University, 1003 Bowers Blvd., Huntsville, TX, 77340-2525, USA. dag006@shsu.edu.
authors.forename: David
authors.identifier: http://orcid.org/0000-0002-4234-0404
authors.initials: D
authors.lastname: Gangitano
mesh_terms: D002188:Cannabis / Q000235:genetics*; D016172:DNA Fingerprinting; D056426:Genetic Loci; D005819:Genetic Markers; D018895:Microsatellite Repeats; D060885:Multiplex Polymerase Chain Reaction; D010802:Phylogeny; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D005819:Genetic Markers
keywords: Cannabis sativa; Forensic DNA; Forensic botany; Reference population; Short tandem repeats