| Maize germplasms are very poor, that enormously hampers the research and utilization of heterosis. It is one focal point that creat breeding material with rich genetic foundtion. Chemical mutation breeding is effective on inducing high frequency and wide scope mutations. If used in maize breeding, it can elevate the breeding level and rich maize germplasms. In this research, mutagenic effects and suitable concentrations of EMS, NaNa-Benzoyl and PYM were studied by means of the seeds of maize inbred treated with these mutagens. The research also studied its suitable concentration and got some mutations, such as early-maturing and special kinds of maize materials when maize pollens of inbred and single-hybrid were treated with EMS in mineral oil. The main results are as follows. l.Mi biological effect of inbred-line seeds treated with three mutagensPhysiological damage can be clearly seen in MI when the seeds of 082 and 095 were treated with different concentrations of each mutagen. Results showed that germination power and germination rate decreased obviously, seedling height, root length and root number were inhibited consequencially and chromosome aberration of root tip cell also increased prominently. The degree of damage corresponded to the concentration. There was sensitive difference between 082 and 095, the latter was more easily effected than the former.The kinds of chromosome aberration were chromosome bridge, fragment of chromosome, laggard and unequal division,ect. Chromosome bridge was the main kind induced by EMS. The main kinds induced by NaNa-Benzoyl were chromosome bridge+fragment and unequal division. Fragment of chromosome was induced mainly by PYM. The highest aberration frequency was 10.21%, induced by 3mM NaN3+5mM Benzoyl. 2.Mi mutation of 082 treated with three mutagens and suitable concentrationThere were all kinds of plant mutation in M2 generation, such as short plant mutation,chlorophyll-dificient mutation and tassel mutation. Some main quantitative characters had no variation, but the mutation frequency of some quantitative characters for example plant height and ear position height was very high.The mutation rates of plant height and tassel branch numbers were 14.17% and 13.46% respectively, which were induced mainly by EMS. The negative rate of plant height was 13.90%. Suitable concentratin should be 0.4% for 082.When treated with NaNs-Benzoyl, the mutation frequency of plant height and ear position height were high, which were 7.73% and 5.44%. The mutagenic effect of 3mM+5mM was better than that of others.When treated with PYM ,mutation rates of ear length and tassel branch number were high, which were 4.81% and 4.77%. Mutagenic effect of PYM was worse than that of EMS and NaNa-Benzoyl. 3.Mutagenic effect of inbred-line treated with EMS-mineral oilIn MI its seed set rate, seedling emergence rate and seedling emergence power were deceased obviously and tassel emergence was effected, while the pollen of 082 were treated with four concentration. Some early-maturing materials that's tassel emergence time were earlier four days than check's were found ,under treatment of 1.43 × 10-3. White grain mutation and light yellow grain mutation that were controlled by hidden gene didn't get in M2 ,but there were mutations in grain shape, ear shape and ear axle colour . 1.43 × 10-3~ 1.67 ×10-3 was a suitable concentration scope. 4.Mutagenic effect of single-hybrid treated with EMS-mineral oilWhen the pollens of single-cross Xinong No.2 were treated with 0.67 ×10-3 ,white grain mutation and light yellow grain mutation were found in M2 ,and sweet grain mutation , white ear and light yellow ear with steady genetic character were got in Ma.
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