J. Christopher

Cytological studies of inter-specific hybrids between Coix lacryma-jobi Linn. (2n = 20) and C. gigantea Koenig ex Roxb. (2n = 12)

SUMMARYThe results of hybridization between C. lacryma-jobi Linn. var. lacryma-jobi Linn. (2n = 20) and C. gigantea Koenig ex Roxb. (2n = 12) and the phylogenetic affinities between these two species are discussed in this paper. C. lacryma-jobi var. lacryma-jobi (2n = 20) is cosmopolitan and the most widely distributed species of this genus, while C. gigantea (2n = 12) occurs as isolated populations in the paddy fields in certain regions of South India. Both species are clearly distinguishable by their morphological features. The karyotype of both species differ very much in the number, size and morphology of the chromosomes. The somatic chromosome number of the hybrid was found to be 2n = 16, consisting of two distinct genomes; the first set of six large chromosomes are probably derived from the gamete of C. gigantea (2n =12), the male parent and the remaining 10 smaller chromosome from the gamete of C. lacryma-jobi var. lacryma-jobi (2n = 20), the female parent. Meiotic studies of the hybrid showed most...

Cytological evidence for the hybrid origin of Coix taxon (2n = 32)

SUMMARYIn the present study, karyological characteristics of two taxa of Coix and their hybrid were described. In Coix taxon (2n = 32) the somatic chromosome morphology showed 12 conspicuously large chromosomes, which show resemblance in dimensions and karyotype to the 12 somatic chromosomes of C. gigantea (2n = 12). The similarity between the basic karyotypes of C. gigantea (2n = 12) and the 12 large somatic chromosomes of Coix taxon (2n = 32) evidences their close taxonomic affinity. The meiotic analysis of the F1 back-cross hybrids (2n = 22) between Coix taxon (2n = 32) and C. gigantea (2n = 12) showed six large bivalents and five smaller bivalents in the PMCs. The presence of six large bivalents in the PMCs indicates that the large chromosomes derived from both parents are genetically homologous and this may be regarded as the most convincing evidence regarding the cytogenetical affinity between the two taxa. It is suggested that Coix taxon (2n = 32) is of hybrid origin, with C. gigantea (2n = 12) as ...