Research And Development Of Technique For N-methyl-N-nitrosourea Mutagenesis On Pollen Germ Cells Of Maize

Maize is the main food crop.Germplasm resources of maize are the basic materials for the cultivation of maize cultivars.With shift of life sciences to the post-genomics,maize science has begun to enter the era of researches on the functional genome and genetic mechanisms regulating character expressions in maize,and goal of maize breeding is also becoming diverse.Under this background,creation of a large number of genetic mutations based on highly efficient technique for chemical mutagenesis is considered to be an important and urgent subject of maize germplasm innovation.N-methyl-N-nitroso urea（MNU）,an efficient mutagen,has been applied to researches on mutageneses of some mammals,microorganisms and rice.In recent years,we have been working on research and development of technique for high-efficiency chemical mutagenesis of maize.The method for the optimal MNU treatment of germ cells of mature pollens in vitro of maize inbred line has been established in the preliminary study in our laboratory.In this study,the mutagenic conditions for the maximum expressed frequency of mutant characters for plants and kernels were determined screening the M₁-M₂ generations derived by the MNU treatments of mature pollens of the maize inbred line（A378）,and a series of homozygous mutants with the various plant and kernel characters were obtained.When the mature pollens were treated with the buffer（pH4.8）containing 0.5 mmol/L MNU and 10 mmol/L phosphate for 40 mins,the expressed frequency of mutant characters in the M₁-M₂generation reached 10.50%.The totaled 381 mutant lines,which had the plant characters such as lethal,dwarf,tiller,low ear height,stripe leaf,roll leaf,narrow leaf display,male sterile,prone stamen,stamen feminization,malformed ear,tufted ear and the kernel characters such as sugaryl,yellowish spot,shrunken,white bottom,dark-yellow bottom,pink,white,waxy,pink spot,were observed from the tested M₁-M₂ populations.Finally,77 homozygous mutants with the series of plant and kernel characters were obtained by the further characterization of characters in the M₃ population.In conclusion,our technique for MNU mutagenesis on germ cells of maize inbred line has the significantly improved efficiency of mutation induction,compared with the reported techniques for the EMS（suspended in paraffin oil）mutagenesis of maize pollens.Its application is expected to promote greatly the efficient development of a large number of genic mutants for the functional-genomic and breeding researches of maize.