Application of ZnO Nanoparticles for Inducing Callus in Tissue Culture of Rapeseed

   Present study has comparatively investigated the effect of zinc oxide nanoparticles (ZnO NPs), ZnO bulk particles (BPs), and relevant metal ions (Zn2+) on the tissue culture of rapeseed (Brassica napus L.) to properly evaluate the impact of ZnO NPs on callus induction. For finding the best hormonal combination for inducing callus, hypocotyl explants were cultured on Murashige and Skoog (MS) media containing different combinations of plant growth regulators. After that, hypocotyl explants were cultured in MS media containing the best hormonal combination, supplemented with four different concentrations (10, 25, 50, 100 mg L-1) of ZnO NPs, ZnO BPs, or equivalent concentrations of Zn2+. Results showed that 10 mg L-1 ZnO NPs can induce callus and shoot regeneration, while the same concentrations of other treatments cannot. Callus growth was significantly retarded by 25, 50 and 100 mg L-1 of all three types of treatment in a dose-dependent manner. Under highest concentration of ZnO NPs, callus was not induced. It can be concluded that optimum concentration of ZnO NPs can be beneficial for inducing callus and/or shoot regeneration in the plant tissue culture.