EFFECTS OF CAFFEINE OR EDTA POSTTREATMENT ON EMS MUTAGENESIS IN SOYBEAN

Seeds of soybean cultivar LD4 were mutagenically treated with EMS (0.3 , 0.5, 0.6, 0.9, 1.5 and 1.8%) for 3 h only or plus caffeine (50 mM) o r EDTA (1 mM) post-treatment for 5 h. The experimental results indicat ed that: (1) of the different concentrations of EMS treatment, the M2 mutation frequency induced with 0.6% EMS was the highest (9.7%). When the EMS concentration was over 0.9%, the mutation frequency decreased rapidly. (2) Of the EMS treatments plus caffeine or EDTA post-treatmen t, the mutagenic effect of 0.6% EMS was the best for inducing morpholo gical variations. Caffeine post-treatment decreased notably the mutati on frequency of EMS treatment; when concentrations of EMS were very hi gh (1.5% and 1.8%), mutation frequencies of EDTA post-treatment were s till 5.0% and 4.88%, but no mutants were found in EMS treatment or plu s caffeine post-treatment. (3) In the M2 mutation spectrum, 11 kinds o f mutant types were observed in EMS treatment or plus caffeine or EDTA post-treatment. Relative frequencies of some mutant types (growth per iod, plant height, grain size, leaf shape and sterility, etc.) were si milar among the three treatments, but EDTA post-treatment could change the relative frequencies of yield characteristics (number of pods and grains, grain weight/plant) induced by EMS treatment only.