Isozyme analysis of the genetic diversity in cultivated and wild species ofAmaranthus

Abstract

Twenty-four accessions of genus Amaranthus belong to ten different species distributed worldwide were analysed using variation of isozymes and allozymes patterns to obtain better insight into genetic diversity and evolutionary relationships within and between these taxonomic entities. Enzyme electrophoresis resulted in clear staining for five enzyme systems including acid phosphatase, alkaline phosphatase, α-esterase, β-esterase and peroxidase. Eighteen putative isozyme loci were scored. Only one locus (Alp2) was found to be monomorphic for all accessions, whereas all other loci were polymorphic. A total of 40 alleles were recognised across all loci. Frequencies of 14 loci were found to discriminate significantly among the 24 studied accessions (p < 0.05). The mean number of polymorphic alleles per locus A = 1.47 and percentage of polymorphic loci P = 38.195% were found to be lower than that reported ones for herbaceous forage plants (A = 1.93 and P = 53.3%). This reduction could be due to geographical isolation, which terminates the gene flow among the studied accessions. The estimates of accessions genetic structure using Nei genetic diversity statistics were calculated. The averages of total heterozygosity (HT) and intra-accessional genetic diversity (HS) were 0.44 and 0.14, respectively. Moreover, the inter-accessional genetic diversity DST has an average of 0.301. These results indicated that inter-accession genetic diversity is higher than intra-accession one. The high levels of genetic differentiation among accessions GST = 0.692, x2 = 48.318, p > 0.05; and the inter-accessional genetic diversity (DST) = 0.301 were probably indicative of low gene flow. This result was confirmed by the gene flow estimates NmW = 0.1164 and indicated the presence of a high percentage of self-pollination in the plant.