Pollen chromosome doubling induced by gibberellin spraying treatment and its effect on microtubule cytoskeleton in Populus bolleana

  Objective  This work was to discuss the feasibility of produce 2n pollen by inducing 2n pollen production via gibberellins (GA₃) and investigating the effects on meiotic microtubule cytoskeleton of pollen mother cells (PMCs) in Populus bolleana, leading to developing a more effective and cheaper chemical mutagen and establishing an effective system of polyploidy breeding for forest tree.

  Method  The observation of the meiotic process of PMCs, the production of 2n pollen induced by GA₃ spraying treatment and its effects on the organization of microtubule were conducted by aceto-carmine (2%) staining and indirect immunofluorescence microscopy using male flower branches as experimental material in P. bolleana.

  Result  It took about 4 days to complete the meisois of PMCs, and the meiotic process within different buds was asynchronous. The meiotic stage, spray time, the interaction of meiotic stage × spay time and spay time × concentration of GA₃ had significant effects on the induction rates of 2n pollen. The optimal treatment combination for inducing pollen chromosome doubling by 50 μmol/L GA₃ solution was given 7 time spraying when PMCs were at meiosis Ⅱ. The highest induction rate was (8.83 ± 3.10) %. Compared with the control group, the radial microtubular structures between two neighboring nuclei were under the optimal conditions, lacked in some treated PMCs, leading to the failure of cytokinesis, nuclear restitution and the formation of triad and consequently a haploid gamete and a 2n gamete.

  Conclusion  Spraying gibberellin could induce chromosome doubling of P. bolleana pollen and obtain 2n pollen in a certain proportion. After PMCs being treated with GA₃, the partial absence of radial microtubular structure between two neighboring daughter nuclei in some PMCs at telophase Ⅱ is found to be responsible for 2n pollen production.