Interactions among genotype, environment and agronomic practices on production and quality of storage onion (Allium cepa L.) - A review

The aim of this review is a wide description of the relationships between growing conditions and bulb yield and quality of onion (Allium cepa L.), focused particularly on long-day cultivars suitable for storage. Marketable yield decreases according to the reduction of crop length caused by the increase of growth temperature. The nutritive requirements of storage onion are highest during the vegetative growth. The application of humic substances and the inoculation of mycorrhizae may enhance bulb growth and quality, mainly under stress conditions. Onion is a slow-growth, shallowrooted crop with non-shading habitus and therefore its productivity is highly dependent on water availability in the soil, proper fertilization and weed control. The shelf-life of onion bulbs is a genetic trait, improvable by efficient crop and post-harvest management, and adequate conditions of bulb storage. The quality of storage onion bulbs is ascribed to several indicators, such as thiosulfonates, pyruvic acid, soluble solids, sugars, and many other biological compounds. This review is also focused on onion quality as affected by the interactions among genotype, environment, farming practices and post-harvest management.