Karyo-morphological consistency and heterochromatin distribution pattern in diploid and colchitetraploids of Vigna radiata and V. mungo

A systematic genetic analysis of colchitetraploids of Vigna radiata and V. mungo in three different generations (C1, C2 and C3) was made using karyomorphology of chromosomes and heterochromatin distribution pattern among them. Autotetraploid of both species were produced using aqueous colchicine (0.15 and 0.20%) and maintained through three successive generations (C1, C2 and C3). The karyomorphological studies showed that the chromosome karyotype remain constant with a consistent asymmetry index among the 3 generations of colchitetraploids and putative diploids in both species. The differential staining technique using fluorophore chromomycin A3 (CMA) showed that CMA+ heterochromatin increase significantly ranging between 1.2 and 2 folds in the colchitetraploids with the CMA+ blocks located mainly on the proximal and terminal regions in the both diploids and autotetraploids. Our study reveal that the karyo-morphology of chromosome tend to maintain a consistency between diploid and colchitetraploids, however, the heterochromatin pattern showed a significant heterogeneity as revealed by the CMA+.