Evolution and improvement of cultivated amaranths with reference to genome relationship among A. cruentus, A. powellii and A. retroflexus

Meiotic studies were carried out in four accessions of three grain species, viz. Amaranthus cruentus, A. powellii and A. retroflexus and their F1 hybrids to elucidate the genome relationships between the cultivated and wild types and the cytogenetical mechanisms involved in speciation. All the three species were morphologically distinct and cytologically uniform with 17 bivalents at metaphase I. Morphologically the interspecific hybrids were either intermediate or had an overall dominance of wild parents. Chromosome analysis at meiotic metaphase I in the F1 interspecific hybrids of A. powellii with the Indian and Mexican accessions of A. cruentus showed an average of chromosome association of 1.0 IV + 0.10 III + 14.78 II + 0.14 I and 1.0 IV + 0.45 III + 14.20 II + 0.25 I and 5.81percent in the former and 8.44percent in the later pollen grain fertility, respectively and that of A. retroflexus with A. cruentus (Indian and Mexican)showed almost similar chromosomal associations. These studies show close genomic homology amongst all these three species involving certain chromosomal aberrations resulting in their evolution.