Mutation frequency in relation to EMS concentration. The relative SNP rates for EMS treatments between 20 and 50 mM were calculated as particular sub-population specific frequencies. Data are based on the mutation screening of eight gene fragments in 7,389 M2 lines. The white and black bars show the accumulated synonymous and non-synonymous (AA changes and truncation) mutations detected for each sub-population. The relationship between SNP frequencies and EMS dosages was calculated based on a non-parametric Spearman rank correlation (coefficient of rs = 0.94 with a significance at p ≤ 0.01).