Cytogenetic characterization of B₁R and BC₁ F₂ backcross progenies of Catla catla (Ham.) and Labeo rohita (Ham.)

The diploid chromosome number (2n) and the chromosomal morphologies of the backcross progenies of Catla catla (Ham.) and Labeo rohita (Ham.) viz.-B₁R and B₁C F₂ developed in Central Agricultural Research Institute, Port Blair, South Andaman, India are reported for the first time through this study. The B₁R backcross generations includes carps developed by hybridization of B₁ backcross female and rohu male. The B₁ backcross individuals were developed by taking F₁ hybrid females from cross of catla female and rohu male hybridized with parental catla male. Similarly, the BC₁F₂ backcross was developed by inter se breeding of B₁ backcross progenies. The conventional Giemsa-Flame drying technique of karyotyping provided first hand information regarding the cytogenetic character of the above two generations of backcross progenies. It was found that, the diploidy in both generations was 50, with variation in chromosomal morphometry i.e.-2n=50: 14M + 10 SM + 10 ST + 16 T/A in B₁R and 2n= 50: 8M +12 SM + 22 ST + 8 T/A. in BC₁F₂.