Genomic variation induced by a low concentration of ethyl methanesulfonate (EMS) in quinoa 'Longli-4' variety

Quinoa (Chenopodium quinoa, 2n = 4x = 36), a super pseudocereal crop, has been introduced into China nearly 60 years. Many excellent varieties have been developed through massive selection; however, few are developed through mutagenesis breeding. In this study, the 'Longli-4' variety, locally cultivated in Gansu province, Northwest China, was selected for experimentation. The grains of 'Longli-4' were treated with ethyl methanesulfonate (EMS) at a concentration of 0.8% for 8 h. Nine plants from independent M₂ families were randomly selected to investigate the mutagenesis effect of EMS on the quinoa genome. The results indicated that the single nucleotide polymorphisms (SNPs) induced by EMS were unevenly distributed across all 18 chromosomes, with an average mutation frequency of 91.2 SNPs/Mb, ranging from 4.5 to 203.5 SNPs/Mb. A significant positive correlation between the number of SNPs and chromosome length was identified through linear model analysis. Transitions from G/C to A/T were the most predominated in all variant categories, accounting for 34.4-67.2% of the mutations, and SNPs were significantly enriched in intergenic regions, representing 69.2-75.1% of the total mutations. This study provides empirical support for the application of low concentration EMS treatment in quinoa breeding.