Negative dominance and dominance-by-dominance epistatic effects reduce grain-yield heterosis in wide crosses in wheat
Philipp H. G. Boeven, Yusheng Zhao, Patrick Thorwarth, Fang Liu, Hans Peter Maurer, Mario Gils, Ralf Schachschneider, Johannes Schacht, Erhard Ebmeyer, Ebrahim Kazman, Vilson Mirdita, Jost Dörnte, Stefan Kontowski, Ralf Horbach, Hilmar Cöster, Josef Holzapfel, Andreas Jacobi, Ludwig Ramgraber, C. Reinbrecht, Norbert Starck, Pierrick Varenne, Anne Starke, Friederike Schürmann, Martin W. Ganal, Andreas Polley, Jens Hartung, Sebastian Beier, Uwe Scholz, C. Friedrich H. Longin, Jochen C. Reif, Yong Jiang, Tobias Würschum
Abstract
The genetics underlying heterosis, the difference in performance of crosses compared with midparents, is hypothesized to vary with relatedness between parents. We established a unique germplasm comprising three hybrid wheat sets differing in the degree of divergence between parents and devised a genetic distance measure giving weight to heterotic loci. Heterosis increased steadily with heterotic genetic distance for all 1903 hybrids. Midparent heterosis, however, was significantly lower in the hybrids including crosses between elite and exotic lines than in crosses among elite lines. The analysis of the genetic architecture of heterosis revealed this to be caused by a higher portion of negative dominance and dominance-by-dominance epistatic effects. Collectively, these results expand our understanding of heterosis in crops, an important pillar toward global food security.