Rewiring the wheat reproductive system to harness heterosis for the next wave of yield improvement.

Abstract

Bread wheat (hexaploid Triticum aestivum) provides an extraordinary 10,000-y story of a new species, established by early farmers, selecting for simple agronomical traits to facilitate efficient and plentiful grain harvest. The genetic changes underlying wheat domestication over thousands of years, however, included not just a collection of beneficial single gene mutations, but also introgressions and whole genome duplication. The hexaploidization event occurred spontaneously in nature, but the resulting wild species did not survive; it is known only in its domesticated form. Evolutionary bottleneck(s) reduced genetic variation of the species, and it was introduced broadly outside its native geographical range and habitat. Nevertheless, modern breeding programs delivered high-yield elite cultivars, which are planted in most major wheat-producing areas of the world. In the face of quickly declining arable land expansion and challenges from climate change, the following question arises: where can we find the next wave of increase in yield and global production of wheat? In PNAS, Kempe et al. (1) describe molecular engineering of an elegant male sterility–fertility restoration system for the exploration of heterosis (hybrid plant vigor) in wheat. In the future, this system could facilitate introduction of hybrid seeds on a large scale.