Hybridization Studies in Coix Species I. Cytomorphological Studies of Coix Taxon (2n=32), C. gigantea Koenig ex Roxb. (2n=12) and the F1 Hybrid

C. taxon (2n=32) was found to be unique in its cytological and morphological features; its karyotype consisted of two distinct genomes. However, karyological studies of C. gigantea (2n=12) revealed a remarkable karyomorphology as the 12 distinctly large somatic chromosomes of this species resembled the 12 large chromosomes of C. taxon (2n=32) in dimensions and karyomorphology.The ability of C. taxon (2n=32) and C. gigantea (2n=12) to hybridize and produce F1 hybrids demonstrates a closer relationship between these two taxa. The hybrids were studied with respect to the morphological characters, karyotype and chromosome association at meiosis. Most of the PMCs of the F1 hybrids show regular pairing among the large chromosomes of both parents, resulting in the formation of six larger bivalents and therefore it is evident that the 12 large chromosomes of both taxa are genetically homologous. Phenotypically the F1 hybrids resembled more closely to the female parent, C. taxon (2n=32), in plant height, size and shape of leaves, size of involucre etc. It has been assumed from the unambiguous cytological evidence that C. gigantea (2n=12) has participated in the origin of C. taxon (2n=32). It is suggested that C. taxon (2n=32) is probably an amphidiploid, arisen by natural hybridization between C. gigantea (2n=12) and C. lacryma-jobi (2n=20) and subsequent doubling of the chromosomes.