ABSTRACTin order to investigate the effects of soluble chitosan on plantlets growth in vitro and increase of minituber yield in potato micropropagation, plantlets of agria cultivar were treated in vitro with soluble chitosan at different concentrations including 0, 5, 15, 50, 150, 500, 750 and 1000 mg/l added to the MS tissue culture medium. Plantlets were subsequently transferred to the greenhouse and minituber yield parameters were evaluated. at the concentrations of 750 and 1000 mg/l of chitosan the culture medium failed to solidify. application of 500 mg/l of soluble chitosan increased the shoot fresh weight, but its lower concentrations did not significantly affect this trait (P < 0.05). The 5 and 15 mg/l of soluble chitosan led to a significant increase in root fresh and dry weight of in vitro plantlets, whereas, higher concentrations, especially 500 mg/l, significantly decreased root fresh weight of in vitro plantlets. application of 500 mg/l chitosan in vitro resulted in improved acclimatization of plantlets in the greenhouse as expressed by significant (P < 0.05) increase in minituber number and yield, compared to the control. The tested lower concentrations had no effect on yield parameters. The present results indicate that soluble chitosan can be successfully incorporated into potato seed production from in vitro plantlets.