F
1 interspecific hybrids (2n=14 and 15) involving
Coix aquatica Roxb. (2n=10) as female were obtained from crosses with 2 cytological races of
C. gigantea Koen. (2n=18 and 20). The large
C. aquatica chromosomes could be distinguished from the small
C. gigantea chromosomes in the F
1 hybrids. Formation of 5 heteromorphic bivalents suggests strong homologies between the chromosomes of the two species which indicates that the
C. gigantea genome has 2 sets of 5 chromosomes each, one of which is homologous to the
C. aquatica genome. Occurrence of association of 3 chromosomes (2
C. gigantea on either side of
C. aquatica) and intragenomic bivalents in
C. gigantea suggest that the second genome is partially homologous to the first one and to that of
C. aquatica. Formation of associations of 3 and a bridge and a fragment at anaphase I suggest that the two genomes are differentiated by at least one translocation and one inversion. In the open pollinated (backcross) progenies, plants with parental and F
1 chromosome associations were also recovered apart from hybrids with varying number of
C. gigantea and
C. aquatica chromosomes.
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