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Genetic Diversity in Genus Amaranthus: From Morphology to Genomic DNA

Reda H Sammour, Radwan SA and Mira M

Some species of the genus Amaranthus are cultivated for their grains or leaves. Some others are useful as colorful ornamentals. The crops are very promising food crop in arid region, due to its resistance to heat, draught, disease and pests. Genetic diversity studies for this genus are essential for providing information for propagation, domestication, and breeding programs as well as conservation of genetic resources. Therefore, this review are devoted for evaluating the genetic diversity between wild and cultivated species and assessing the evolutionary relationships between the cultivated species and their putative species using wide array of available markers. A wide morphological variability between Amaranthus species and different accessions of vegetable Amaranthus was reported. This variability was useful in cultivar improvement for agronomic traits. The chromosome number for Amaranthus species is normally 2n=32 (n=16), but occasionally it is 34 (n=17). It has been suggested that the gametic number n=17 has originated from n=16 through trisomy. Karyotypes are mainly comprised of many metacentric chromosomes and few submetacentric ones. There is a variation in chromosome size between Amaranthus spp. and the accessions of each species. Based on cytological data, it was proposed that A. hybridus is the putative ancestors of the cultivated amaranths. Buffer extracts of seed storage proteins of taxa of Amaranthus spp. analyzed on SDS-PAGE under reducing conditions divided Amaranthus taxa into two groups; group with n=17 and the other group with n=16, indicating the relation between the chromosome number and the electrophoretic pattern. The electrophorectic patterns of the seed proteins of amaranth species can be used to discriminate between Amaranthus species. Isozymes markers showed low heterozygosity in the New World populations of Amaranthus. A wide genetic distance was detected between crop and weed species.Alleles at several loci proved to be diagnostic of the crop and weed groups. High levels of interspecific and intraspecific variation were found between Amaranthus spp using isozyme marker. Biochemical and molecular data sets supported a monophyletic origin of grain amaranths, with A. hybridus as the common ancestor. The molecular data showed genetic variation among and within the populations of Amaranthus spp. and indicated that genetic diveristy within wild was lower than grain species.