Karyotype Analysis in Three Morphological Forms of Colocasia fallax Schott.

Abstract

The 3 forms of Colocasia fallax Schott. complex, namely green petiole form, light purple petiole form and deep purple petiole form, available in Bangladesh were studied cytogenetically to confirm their taxonomic status after staining with orcein and CMA. The green petiole form and the deep purple petiole form were found to possess 2n=28 chromosomes whereas 2n=30 chromosomes were observed in the light purple petiole form. The centromeric formula was determined as 20 m+8 sm in the green petiole form, 26 m+2 sm+2 ac in the light purple petiole form and 24 m+4 sm in the deep purple petiole form. Acrocentric chromosomes were found only in the light purple petiole form. 4 satellites were found in the green petiole form after orcein staining while only 1 satellite observed in CMA staining of the same form. These satellites showed stain specific nature in this form. 8 and 11 CMA positive bands were found in the green petiole form and the deep purple petiole form, respectively. Only 2 centromeric CMA positive bands were found in the light purple petiole form. Different CMA banding pattern and percentage of GC-rich repeats were found in these 3 forms. CMA banding was able to identify some chromosomes in the green petiole form and the deep purple petiole form. The diploid chromosome numbers and overall karyotypic features indicated that the light purple petiole form possessed quite different genomes than the other 2 forms and thus may be placed in a different taxonomic rank. Except a minute difference in the karyotypic features, the green petiole form and the deep purple petiole form possessed almost entirely similar genomes and therefore could be considered as different varieties of Colocasia fallax.