A Century of Understanding and Harnessing Heterosis

Heterosis has shaped modern plant breeding since Darwin's 19th century observations that outcrossing restores vigour lost through selfing. While 100 years old, its mechanistic basis and deployability remain actively debated. Classical models of dominance, overdominance and epistasis provided the foundation for hybrid breeding and converted maize into a globally dominant crop through heterotic group formation, scalable seed systems and intellectual property protection. Advances in genomics and systems biology reveal that heterosis is not solely a consequence of allelic complementation but emerges from coordinated regulatory and metabolic reprogramming. Hybrids exhibit non‐additive gene expression, altered circadian clock regulation, epigenetic remodelling via DNA methylation and small RNAs and improved metabolic efficiency, including enhanced redox homeostasis and reduced protein turnover. This review synthesizes historical and contemporary perspectives on heterosis across different crops emphasizing how reproductive biology, seed production efficiency and economic constraints shape the feasibility of hybrid systems. It further evaluates population‐based strategies and emerging technologies such as synthetic apomixis, which offer the potential to stabilize hybrid vigour across generations. By integrating mechanistic insight with breeding practice and seed system realities, this review reframes heterosis as both a biological phenomenon and a deployable technology, highlighting pathways towards more sustainable and inclusive crop improvement.