Superiority of F1 over mid-parent is called:
Relative heterosis, also termed mid-parent heterosis, quantifies superiority of F1 over average performance of its two parents. Mathematically calculated as difference between F1 and mid-parent value MP equals mean of P1 and P2 divided by MP multiplied by 100 to express percentage. Positive estimates indicate dominance and additive by additive interactions aggregating across quantitative trait loci governing yield components, chlorophyll content and stress tolerance. Mid-parent represents expected additive performance under no dominance, so deviation signals non-additive gene action. Although
Ref: Falconer Intro Quantitative Genetics heterosis definitions; Singh BD Relative heterosis formula; Acquaah Chapter Heterosis metrics.