Effectiveness of Sodium Azide Alone Compared to Sodium Azide in Combination with Methyl Nitrosurea for Rice Mutagenesis

Rice seeds of the temperate japonica cultivar Kitaake were mutagenized with sodium azide alone and in combination with methyl nitrosourea. Using the reduced representation sequencing method Restriction Enzyme Sequence Comparative Analysis (RESCAN), the mutation densities, types and local sequence context were determined in the resulting M2 generation mutants. The results indicate that sodium azide is as effective alone as in combination with methyl nitrosourea in generating mutations in rice. In both cases, GC>AT transitions were the predominant mutation type and similar local sequence contexts were observed (5’-G-G-R-3’ for sodium azide, 5’-R-G-R-3’ for sodium azide plus methyl nitrosourea). Differences in local sequence context with those reported for another common chemical mutagen, ethyl methanesulfonate, suggests that rice mutant populations developed by combining mutants derived independently from sodium azide and ethyl methanesulfonate may exhibit a broader spectrum of mutations and mutant phenotypes.