Breeding new varieties for controlled environments.

Agricultural production in controlled environments is increasingly feasible, and may play an important role in providing nutrition and choice to growing urban centres. New technologies in lighting, ventilation, robotics and irrigation are just a few of the innovations that enable production of high-value specialty crops outside of a traditional field setting. However, despite all of the advances in the hardware within the plant factory operation, innovation of the most complex machine has been neglected - the plant itself. Indoor agricultural operations typically rely on legacy varieties, plants selected and bred for field conditions. In the field, phenotypic stability is paramount, as production must be consistent in an unpredictable and changing environment. However, the controlled environment affords focus on different breeding priorities as environmental flux, pests, pathogens and post-harvest quality are less formidable barriers to production. On the contrary, breeding for controlled environments shifts the focus to a completely different set of plant traits, such as rapid growth, performance in low light environments and active manipulation of plant stature. Instead of breeding for phenotypic stability, plants may be bred to maximise genetic plasticity, allowing specific traits to be presented as a function of the quality of the ambient light spectrum. In this scenario plant varieties may be grown with optimal size, supporting a focus on consumer traits like flavour or accumulation of health-related compounds. Gene editing may be a central technology in the production of designer plants for controlled environments. This review considers the opportunity for breeding for controlled environments, with a focus on a revision of priorities for controlled-environment breeders.