Evolution and improvement of cultivated amaranths with reference to genomerelationship 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 hybr ids to elucidate the genome relationships between the cultivated and wild t ypes and the cytogenetical mechanisms involved in speciation. All the three species were morphologically distinct and cytologically uniform with 17 bi valents at metaphase I. Morphologically the interspecific hybrids were eith er intermediate or had an overall dominance of wild parents. Chromosome ana lysis 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 5.81% in the former and 8.44% in the la ter pollen grain fertility, respectively and that of A. retroflexus with A. cruentus (Indian and Mexican) showed almost similar chromosomal associatio ns. These studies show close genomic homology amongst all these three speci es involving certain chromosomal aberrations resulting in their evolution.