Abstract
Cannabis has been used as a source of nutrition, medicine, and fiber. However, lack of genomic simple sequence repeat (SSR) markers had limited the genetic research on Cannabis species. In the present study, 92,409 motifs were identified, and 63,707 complementary SSR primer pairs were developed. The most abundant SSR motifs had six repeat units (36.60%). The most abundant type of motif was dinucleotides (70.90%), followed by trinucleotides, tetranucleotides, and pentanucleotides. We randomly selected 80 pairs of genomic SSR markers, of which 69 (86.25%) were amplified successfully; 59 (73.75%) of these were polymorphic. Genetic diversity and population structure were estimated using the 59 (72 loci) validated polymorphic SSRs and three phenotypic markers. Three hundred ten alleles were identified, and the major allele frequency ranged from 0.26 to 0.85 (average: 0.56), Nei’s genetic diversity ranged from 0.28 to 0.82 (average: 0.56), and the expected heterozygosity ranged from 0.28 to 0.81 (average: 0.56). The polymorphism information content ranged from 0.25 to 0.79 (average: 0.50), the observed number of alleles ranged from 2 to 8 (average: 4.13), and the effective number of alleles ranged from 0.28 to 0.81 (average: 0.5). The Cannabis population did not show mutation-drift equilibrium following analysis via the infinite allele model. A cluster analysis was performed using the unweighted pair group method using arithmetic means based on genetic distances. Population structure analysis was used to divide the germplasms into two subgroups. These results provide guidance for the molecular breeding and further investigation of Cannabis.
Highlights
Cannabis is an erect annual herb that belongs to the family Cannabaceae
The most abundant simple sequence repeat (SSR) motifs were generally detected on chromosome 5 (12,099), whereas chromosome 10 showed the lowest number of SSR motifs (5277)
The results show that the major allele frequency (MAF), number of alleles (Na), number of alleles (Ne), I, H, polymorphism information content (PIC), and He were lower in local cultivars than in wild accessions; that is, the genetic diversity of wild accessions was higher than that of the domesticated accessions
Summary
Cannabis is an erect annual herb that belongs to the family Cannabaceae. Its cultivation, as a source of fiber, was first documented in China and, subsequently, spread throughout the world (Li, 1973; Small and Cronquist, 1976). As one of the oldest plants, Cannabis has been used medicinally for more than 10,000 years in China, and this is documented by Emperor Shen. Genetic Diversity and Structure of Cannabis sativa. There are many standards to classify Cannabis species. Cannabis is classified into four types, namely wild, fiber, oilseed, and psychoactive types. Cannabis is recognized as hemp and marijuana. Based on the degree of domestication, Cannabis is classified as wild, domesticated, and intermediate types (Chandra et al, 2017). Previous studies demonstrate substantial genetic diversity between marijuana and hemp lines. Molecular markers have been utilized to the identify sexual phenotypes and chemotype-determining factors and elucidate the genetic diversity of Cannabis species (Mandolino and Carboni, 2004)
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