Effect of Storage Duration and Temperature on Sets Loss and Bolting of Onion

Onion sets of two cultivars - Rawska and Jetset F₁ were calibrated into three grades depending on the diameter of onion (11-15, 16-20 and 21-25 mm). From October to March, sets were kept in the following conditions: I - 24 weeks at 0-1°C, II - 15 weeks at 0-1°C, then 9 weeks at 18-20°C, III - 11 weeks at 0-1°C, then 13 weeks at 18-20°C, IV - 24 weeks at 18-20°C. The storage loss caused by complete drying up, sprouting into leaves and occurrence of disease symptoms were determined. The sets left over after evaluation of storage loss were planted in the field in order to determine bolting of onion. Cold storage (0-1°C) for 24 weeks reduced loss but stimulated bolting. In the case of Jetset F₁, warm storage (18-20°C) for the last 9 weeks of the 24 weeks' experimental storage period practically eliminated bolting. The sets of Rawska required longer exposures of 18-20°C at the end of storage for suppressing of inflorescence development than Jetset F₁. The smaller onion sets were kept the shorter the duration of warm storage required to reduce bolting. The longer onion sets were stored at 18-20°C the greater storage loss were noted.