Improvement of Onion Through Accelerated Approaches

The bulb onion (Allium cepa L.) is grown on all continents except Antarctica and is prized by essentially all of the world’s cultures for its flavour and health-enhancing attributes. Both open-pollinated (OP) and hybrid cultivars are commonly grown, with hybrids predominating in most regions of the world. Hybrids are produced using cytoplasmic male sterility (CMS), and different sources of CMS are commercially used. Onion breeders focus primarily on bulb characteristics such as colour, shape, soluble solid content, pungency and flavour, storage ability and health-enhancing attributes, as well as plant characters such as resistances to diseases, pests and bolting. Important characteristics for seed production include uniform flowering, straight seed stalks, stable expression of male sterility and seed yield. Most of these traits show moderate to high heritability and therefore respond to selection. Due to the biennial generation time of the onion, the development of value-added populations and hybrids is a time-consuming and expensive process. The use of biotechnological approaches, such as marker-aided selection, production of doubled haploids, gene editing and cytoplasmic conversions, offers great promise for population improvement and hybrid development addressing changes in consumer preference and production environments.