Heterosis in wheat: mechanisms, benefits, and challenges in hybrid development

Heterosis, or hybrid vigour, has been exploited by plant breeders and grain growers for more than a century, and open-pollinated crops such as maize have been successfully commercialised. However, the full genetic potential of heterosis has yet to be realised and the fundamental mechanisms underlying this complex process are poorly understood. The challenges of hybrid seed production in self-pollinated crops, including cereals such as wheat and barley, have prevented the widespread exploitation of heterosis in these crops. Focussing on wheat, this review details current understanding of the genetic control of heterosis and explores the efficacy of different methods for producing F1 hybrids. We posit that the mechanisms underlying heterosis are probably a combination of multiple or all current theories, and that the conversion of inbred crops such as wheat into hybrid breeding systems can be further enhanced using a complete genic system, lessening the need for current, more complex hybrid production systems.