Original Article Cytogenetical evidences of abnormal meiosis and 2n pollen formation via colchicine in microsporogenesis of Brassica campestris L.

Cytogenetical studies have been undertaken to assess the consequences of induced colchiploids and its reflection on meiotic index (MI) and pollen viability (PV) in Brassica campestris L. during microsporogenesis. Colchiploids of Brassica obtained at 0.3%-0.5% doses were administered as meiotically stable since they possessed MI and PV between 90%-100%. However, utmost dose (0.6%) displayed significant meiotic instability (p<0.05) i.e. MI and PV ranged from 85.55%79.81% and 87.72%-81.56%, respectively. Microsporogenesis analysis revealed the occurrence of several meiotic manifestations that might have incited reduction in MI and PV with the increasing doses. Abnormal meiotic course had also resulted into disturbed post-meiotic products namely monads, dyads, triads and polyads with or without microcytes. Such disturbed post meiosis has affected pollen viability considerably causing declining spectrum of pollen viability in a dose dependent manner. In few PMCs (pollen mother cells) inter cellular chromatin migration were also discerned which surely seemed to be the probable cause of syncytes leading to low level polyploidy and higher frequency of polyads at ascending doses. Markedly large sized pollen grains were also discerned. Interestingly, these larger pollen grains were fertile and showing the probability of such pollen grains being unreduced (2n) in genetic constitution. Hence present research reports the potential cytogenetical manipulating properties of colchicine through which stable polyploid lines could be raised and used for creating genetic variability in Brassica crop with altered chromosome combinations.