In order to optimize the hormone content and ratio of the callus medium of Lespedeza davurica Schindl.and to clarify the optimal conditions for callus and seeds mutagenesis by EMS,the effects of different hormone ratios on the callus induction using seeds of L.davurica as the experi-mental materials were investigated,and different combinations of treatment time and concentration were set for callus(EMS:0.3％and 0.9％,time:2 hours and 6 hours)and seeds(EMS:0.4％and 0.8％,time:6 hours,8 hours and 10 hours)to investigate their effects on the differentiation coefficients of callus and plant viability,as well as seed germination rate,seed germination potential and seedling phenotypic variation.The results showed that the optimal hormone ratio for seed callus induction in L.davurica was 0.25 mg/L NAA+0.5 mg/L 6-BA+0.5 mg/L 2,4-D,in which the callus induction rate was 94.9％.The optimal EMS mutagenic condition for L.davurica callus was 0.3％mutagenicity for 6 hours.With this condition,the differentiation coefficients of the callus(46.31％)and the relative survival of the plants(47.78％)were close to the semi-lethal range,and the number of roots,root length,and average plant height were less negatively affected than in the high EMS treatment.The optimal EMS mutagenic condition for L.davurica sseeds was 0.8％and mutagenicity for 10 hours.Under this condition,seed germination,germination potential and seedling survival were 53.61％,51.06％and 53.28％,respectively,and similarly all were close to the semi-lethal range.Meanwhile,significant morphological variation was observed in the leaves of multiple seedlings under this mutagenic condition.The experiment not only enriched the mutant library on the base of the orig-inal germplasm resources of L.davurica,but also provided a basis for the subsequent research on mutation breeding of L.davurica.
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