Study On EMS Mutagenesis And Salt-tolerant Mutant Screening Of Betula Platyphylla

Betula platyphylla Suk.is a species of genus Betulaceae in family Betula.It is a kind of deciduous tree with beautiful shape,straight and elegant white trunk and yellowish autumn leaves.It has high ornamental value and economic value.Chemical mutation technique proves to be an effective breeding method due to the high mutagenesis frequency,easy operation and simple steps.In this study,Betula platyphylla has been used as the experimental material.After establishing the in vitro regeneration system,the seeds and callus were treated with different concentrations of EMS solution and mutagenesis time.The suitable mutagenic dose has been determined.The callus and plantlet has been treated with different concentrations of?Na2CO3and NaHCO₃?mixed solution as the selection pressure.The saline-alkali resistance threshold was screened.The callus was co-treated with half a fatal dose of EMS solution and a mixed solution of?Na2CO3 and NaHCO3?.The saline-alkali resistance candidate mutants have been screened and identified by the relevant physiological indicators.The research results provide a theoretical basis for further screening for saline-alkali resistance mutants of Betula platyphylla.The main results are as follows:1.The stems segment of plantlets of Betula platyphylla were used as explants.The suitable medium for callus induction was MS+3.0 mg/L 6-BA+0.5 mg/L KT+20 g/L sucrose,and the induction rate was 84.44%;The suitable medium for adventitious bud differentiation was WPM+0.4 mg/L 6-BA+20 g/L sucrose,and the differentiation rate was 87.7%;The suitable medium for shoot bud proliferation was WPM+0.3 mg/L 6-BA+20 g/L sucrose,and the proliferation coefficient could reach 9.38;The best proliferation medium for stem section was WPM+0.4 mg/L 6-BA+20 g/L sucrose with a proliferation coefficient of 4.33;The suitable rooting medium for seedlings was WPM+1.0 mg/L NAA+20 g/L sucrose,and the rooting rate was 100%,and the average number of roots was 9.38.2.Treatment of callus with 0.4%EMS solution for 7 h and 1.0%EMS solution for 5 h was a suitable mutagenic dose,and the survival rate was 49.94%and 50%.Treatment of callus with0.4%EMS solution for 1 h was a suitable mutagenic dose,and the survival rate was 54.07%.3.The the saline-alkali resistance threshold of callus and plantlet of Betula platyphylla was4 mmol/L.4.Selected saline-alkali resistance candidate mutants have been identified by relevant physiological indicators.The results showed that the SOD activity and chlorophyll content of the salt-tolerant mutants were higher than those of the control group,and the MDA content was lower than that of the control.