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SUMMARY
The external morphology and cytology has been studied in diploid and tetraploid male and female plants of Coccinia indica. The tetraploids exhibited gigas characters.
In the somatic cells, it was observed that the chromosomal constitution of the diploid was 24 and that the male was heterogametic with 22A + XY chromosomes and the female was homogametic (22A + 2X). The X and Y were SAT chromosomes. Due to its size the Y chromosome could be differentiated from the autosomes and X chromosomes but the X chromosomes could not be differentiated from the autosomes. The somatic number of chromosomes in the autotetraploids was 48 with the constitution 44A + 2X + 2Y in the male and 44A+4X in the female.
The progeny from crosses between diploid female and tetraploid male had a proportion of triploid males, as compared to the females which was much higher than expected on the basis of random 2:2 distribution of chromosomes. This is obviously due to the preferential pairing observed between the sex chromosomes (X and Y) of the polyploid male parent. The XYY combination was not found among the male triploids.
The Y chromosome appears to have a strong influence towards the expression of maleness.