Sprout Inhibition of Onions by Ionizing Radiation

Part IV. Effect of post-harvest treatment on extension of irradiation time for storage of onions.

Abstract

The dormancy period of onion, Cult. "Sapporoki" was about one month after harvest. Sensitivity of onion to irradiatian gradually decreased after the dormancy period accompanied by growth of inner bud. At this stage, inhibition of sprouting could not be achieved when the same was irradiated after three months of harvest. Complete suppression of sprouting was observed in onions irradiated with 3 to 7 Krad during the dormancy period.
Usually, harvested onions are dried for two weeks before irradiation. Inhibition of sprouting and keeping quality were attained with the dose of 3 to 7 Krad when freshly harvested oaions were irradiated either before or during the drying treatment for storage.
Irradiation period could be extended by low temperature storage of onion after harvest. Growth of inner bud suppressed at 3-5°C even after three months of storage and the length of inner bud was similar to that of one month old onion. Thus, sprouting was inhibited by irradiation and apical dominence observed for three months from the harvest date when onions were stored at low temperature.
Browning of buds was observed in irradiated onions during storage. This was prevented by low temperature storage and such onions have retained good market quality for one month when transferred from low temperature to ambient temperature.