Interaction effects of chitosan, benzyladenine, and gibberellic acid on in vitro proliferation of M26 apple rootstock

The present study was conducted to evaluate the proliferation ability of M26 apple rootstock on the MS medium supplemented with various concentrations of crab chitosan, gibberellic acid (GA(3)), and N6-benzyladenine (BA). Combination of 120 mg.L (-1) chitosan and 0.5 mg.L (-1) BA in the absence of GA(3) was most suitable for the proliferation after 12 weeks. Without chitosan, total number of shoots increased by increasing BA concentration, but the shoots led to rosette and dense growth, developing tiny yellowish leaves with soft and watery tissues. Shoots taller than 3 cm were obtained by 0.1 or 0.3 mg.L (-1) GA(3) in combination with 120 mg.L (-1) chitosan, but leaves were small with yellowish green color. These results indicated that chitosan can be used as a growth stimulator in combination with a minor amount of plant growth regulators to improve the proliferation rate of in vitro cultured M26 apple rootstock.