Studies On Screening Techniques For Salt Tolerance Evaluation Of Induced Mutants Of Apple Stock In Vitro

In the present experiment, the screening techniques for salt tolerance and induced mutants were studied, and primary screening system for salt tolerance evaluation was established. Also, the difference in salt tolerance of induced plantlets was compared.1.Induction treatments. Both Sodium azide (NaN3) and Ethyl methanesulfonate (EMS) were used to treat the leaves in vitro of the experimental materials. The results showed that the survival and regeneration rates of induced leaves were affected seriously with the increase of mutagen concentrations and the prolongation of treatment time. Two different methods were applied as below: (1) Treatment with mutagen solution. (2) Treatment with mutagen added to medium. With NaN3, both methods were ideal choices, but with EMS, treatment with mutagen solution was better.In the experiment, about 60% lethal dose of the mutagens was used as the selective indexes of optimal mutagen concentrations and treatment time, the best combination of treatment were the follows:Treatment with NaN3 solution: (l.Ommol ?L''~2.0 mmol ?!/')+(lh~2h);Treatment with NaN3 added to medium:(0.02mmol 昄''~0.05mmol 昄/')+(2d~ 3d);Treatment with EMS solution: (0.1%~0.2%)+(lh~1.5h).2.Selection of NaCl critical concentration. Subcultural mediums containing different NaCl concentrations were used as selective medium for induced plantlets. With injury rate of control was 100%, but that of the induced plantlets were lower than that of control and there were some uninjured plantlets, the critical concentration 0.7% of NaCl was determined. Under the critical concentration, different induced plantlets (60Co- Y , NaN3, EMS) showed different variant rate:23.33%,16.67%,3.33%.3.Determinations for variant plantlets. Higher salt tolerance existed in39plantlets with higher injuty index and SODase activity, lower ratio of MDA content of induded plantlets and control, lower cell membrane permeability, or lower ratio of cell membrane permeability of induced plantlets and control. It was recommended that injury index, SODase activity, content of MDA and Cl~,cell membrane relative permeability could be used as the evaluation indexes of salt tolerance; Protein content in leaves could not be used as the evaluation indexes.4.Comparison of salt tolerance of variant plantlets. The salt tolerance of variant plantlets were higher than that of control. The salt tolerance of variant plantlets irradiated by 60Co- v was the highest.