Ethylene Inhibits Sprouting of Onion Bulbs during Long-term Storage

Abstract

The protrusion of sprouts is a major cause of loss of dry onions (Allium cepa L.) during extended storage. Sprouting is conventionally suppressed by treating onions with maleic hydrazide (MH) before harvest. More recently, ethylene was reported to inhibit sprout growth in stored onions, but commercial use of ethylene has been limited. Therefore, the objective of this study was to assess the effectiveness of ethylene on sprout suppression of five commercial cultivars of onions during storage and compare its effectiveness with and without MH treatment. Onions treated with MH were stored for up to 9 months at 1 °C in atmospheres with and without ethylene in a series of experiments conducted over six seasons. Differences in sprout elongation and protrusion were observed during storage in air among the five cultivars. Storage in ethylene was effective in inhibiting sprout elongation and root growth of onion bulbs in all cultivars, with concentrations of 7 µL·L−1 ethylene being more effective than 1 µL·L−1 ethylene. Delaying application of ethylene by 4 months was less effective in inhibiting sprout elongation than continuous treatment. Ethylene provided greater sprout suppression than MH treatments alone and could serve as a replacement for MH.