Effects of cultural practices at harvest on onion (Allium cepa) bulb quality and incidence of bacterial soft rot and fungal moulds after simulated shipping

Abstract

A field study was carried out to investigate the effects of cultural practices at and after harvest on onion (Allium cepa) bulb quality and incidence of storage rots and fungal moulds after both ambient and refrigerated simulated shipping. Onion plants were lifted at one of two stages of maturity, cured under three moisture conditions, and topped at two different times. Refrigerated simulated shipping reduced the incidence of rots, even in bulbs cured under dry or ambient moisture conditions, from 2.6% to 0.9%. Refrigeration also reduced the severity of surface moulds; the percentage of bulbs with commercially undesirable levels being reduced from 54% to 21%. Refrigeration also resulted in outturn of a larger proportion of bulbs with green‐yellow skins. The combination of topping before field curing and wet conditions during field curing increased the incidence of rots in bulbs after simulated shipping in ambient and refrigerated conditions. Dry field curing conditions increased the incidence of skin splitting in bulbs lifted at 90% top‐down, but not in those lifted at 25% top‐down, where average incidence of splitting was less than 1%. Lifting at 25% top‐down resulted in a greater proportion of bulbs with two or more intact outer skins, and reduced the incidence of skin splitting. Modification of husbandry practices, monitoring of the weather during harvest, and refrigerated shipping are recommended as measures to reduce the incidence of bacterial soft rot and improve the quality of onion bulbs in storage and transit.