Physiological factors affecting onion (Allium cepa l.) storability
Coolong, Timothy Wayne
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The relationships between bulb firmness and several physiological factors were tested in onion (Allium cepa L). Firmness was found to be related to the amount of total cell wall material in bulbs, with the firmest bulbs having nearly twice the amount of pectin and cellulose as the softest bulbs. This was confirmed visually using transmission electron microscopy. Dry matter content was also correlated to bulb firmness. Additionally, pectin methylesterase and polygalacturonase activities were highest in those bulbs which displayed the greatest rate of softening during storage. The effects of calcium chloride fertility as a method to improve firmness were also studied. Bulb firmness responded positively to supplemental calcium chloride. However, no link between pectin concentration and calcium regime could be established. In a third study, a real-time pcr assay was developed for the detection and quantification of Botrytis allii, the causal agent of neck rot in onion. Neck rot is the most severe storage disease in onion production. The assay allowed for the detection of 1 µg of B. allii mycelia in onion tissue.