FIGURE 1.

Al and proton tolerance of Arabidopsis thaliana accessions. (A) Distribution of the relative root lengths (RRLs) of 206 A. thaliana accessions under Al and proton stress conditions (CV; coefficient of variation, H_b²; broad-sense heritability). Seedlings were grown hydroponically for 5 days in either Al (5 μM Al, pH 5.0)/proton (0 μM Al, pH 4.6) solutions or a control solution (0 μM Al, pH 5.0). Five biological replicates of root length were used for calculation of relative root length [RRL; root length under stress conditions/root length under control conditions (%)] (n = 5). (B) Correlation between Al and proton tolerance among A. thaliana accessions. (C) Boxplot of Al and proton tolerance for 112 representative accessions from six ancestral subpopulations inferred from STRUCTURE (EE; Eastern Europe, NA; North America, CA; Central Asia, WE; Western Europe, NE; Northern Europe, SE; Southern Europe). The values under EE-SE represent the number of representative accessions of each subpopulation (Supplementary Table S1). Significant outliers from the mean RRL for each subpopulation are indicated by open circles above or below the boxplots. The mean RRL value for the whole population is represented by a dashed line. Asterisks above the boxplots indicate a significant difference from the mean RRL value for the whole population (permutation test, p < 0.05). Different letters indicate statistically significant differences in mean RRL value among the six subpopulations (Tukey’s HSD test, p < 0.05).