Heterosis occurs in epiHybrids. A, Experimental setup. Lines are depicted schematically as one chromosome with the numbers indicating the epiRIL identifier (e.g. 371 and 492) and the respective epiHybrid (e.g. 371H and 492H). B, Genome-wide 5mC levels (y axis) of the Col-wt line in green and the epiRIL parental lines in salmon. Numbers indicate the epiRIL identifiers. The 5mC levels were calculated as the proportion of methylated DNA immunoprecipitation probes with respect to the total amount of probes. C, Col-wt, epiHybrid 232H, and epiRIL 232 at 13 DAS as an example for high-parent heterosis. D to F, Three classes of phenotypic effects monitored in the epiHybrids. The black dashed lines indicate the MPV. The green and salmon peaks indicate the mean performance of the parental lines. The white dashed lines indicate the mean performance of the epiHybrids. G, Phenotypic effects in six traits monitored across the 19 epiHybrids. The columns at the right summarize positive and negative heterotic effects per trait. H to J, Examples of epiHybrids exhibiting high-parent heterosis in LA and HT (H and I) and low-parent heterosis in FT (J) Error bars represent ±1 se. Deviation from high parent or low parent is shown in percentage.