Sodium azide mutagenesis generated diverse and broad spectrum blast resistance mutants in rice

Genetic mutagenesis can create novel alleles that do not exist in nature germplasms and has been widely used for the improvement of crop plants. Rice blast caused by Magnaporthe oryzae is one of the most destructive disease for rice production. For now, limited mutation-derived varieties associated with blast resistance were reported. In this study, a rice TNG67 mutant pool, developed by using sodium azide (SA) mutagenesis, contained more than 3000 pure mutant lines (SA mutants), were utilized. 50 SA mutants derived from rice blast susceptible variety TNG67 as well as other commercial and differential varieties were challenged with 89 blast isolates collected in Taiwan to understand their blast resistance spectrum. The results showed that SA mutants displayed different responses to M. oryzae, ranging from highly susceptible (6.7%) to highly resistant (100%). Seven mutants showed broad-spectrum resistance against the tested blast isolates. Bidirectional interaction analysis revealed a better understanding of plant-pathogen interaction. Our studies demonstrate that sodium azide mutagenesis is an efficient and effective method to induce rice blast resistance and generate valuable genetic resource for blast resistance improvement.