19.11 Sequence Characterized Amplified Regions (SCAR)
Analysis of Cannabis
The use of SCAR markers has been primarily for the development of techniques to
assist in the separation of male and female plants in hemp (Mandolino et al. 1999 ),
as described below.
19.12 Single-Nucleotide Polymorphism (SNP)
and Genotype-by-Sequencing (GSB) Analysis
of CannabisIn a study by Sawler et al. ( 2015 ), a sample population consisting of 81 marihuana
strains (including land races and cultivated forms) and 43 hemp strains and cultivars
were compared at the genome-wide level using a genome-by-sequencing approach.
A total of 14,031 single-nucleotide polymorphisms were analyzed to infer relation-
ships between marihuana (inclusive ofsativaandindicatypes) and hemp. The results
demonstrated that marihuana strains were significantly differentiated from hemp, and
thatindicatypes of marihuana (based on ancestry) could be differentiated fromsativa
types. However, some purportedindicaandsativatypes could not be supported from
the molecular data, suggesting an inaccuracy in reported ancestry of some marihuana
strains. Furthermore, a comparison of 81 marihuana strains revealed that not all of
them were genetically unique. Some strains with different names were genetically
similar, and some strains with identical names were genetically different. A similar
observation was reported by Dufresnes et al. ( 2017 ). Sawler et al. ( 2015 ) concluded
that the genetic identity of a marihuana strain cannot be reliably inferred from its name
or from its reported ancestry. Our results from ISSR analysis also showed that mar-
ihuana strains bearing similar names were separated into different clades, and strains
with different names clustered together in closely-related groups.
19.13 Markers to Assess the Sex Phenotype in Cannabis
The identification of male and female plants originating from a population of
germinated seeds of cannabis is a key aspect in the commercial production of
marihuana. Male plants need to be identified and rouged out prior toflower
development to avoid potential pollen spread, which could result in seed devel-
opment if pollination were to take place. The identification of male-sex specific
markers has received considerable interest in efforts to develop those into methods
that can assist in separation of male from female plants early during development.
By initially using RAPD markers to separate male from female plants in dieo-
cious hemp, Sakamoto et al. ( 1995 ), showed the presence of two DNA fragments
412 Z.K. Punja et al.