Cytological, Cytochemical and Electrophoretic Distinction of a Dioecious Cucurbit, Coccinia indica

Abstract

Chromosome studies, in situ estimation of 4C nuclear DNA content and isoesterase profiles of vegetative propagules were carried out in dioecious Coccinia indica Wight and Arn. Somatic chromosome number 2n=24 though recorded in both sexes, a distinct heteromorphic pair of sex chromosome is found in male plants. Diploid males are heterogametic with 22+XY and females are homogametic with 22+XX. The somatic chromosomes are generally short with median and submedian constrictions except the metacentric Y chromosome which is conspicuously large. The relative size differences of chromosomes indicate a tendency towards progressive asymmetry. 4C nuclear DNA content shows marked variation in relation to sex and a positive linear relationship between the amount of the DNA and the total chromosome length is recorded. The average packing ratio (APR) of male and female plants differs which suggests a differential organisation of mitotic chromosome in relation to sex. Differences in the isoesterase pattern obtained in the vegetative reproductive structure indicate that it could also be used as an important biochemical marker for identification of sexes.