2. Materials and methods
2.1. Field experiment
The present experiment was conducted in Changnyeong county(35◦N, 128◦E), in southeastern Korea, in 2010–2011 growing sea-son. In the county, onions were grown on a total of 1152 ha(KOSTAT, 2012). Experimental sites came from 16 long-termonion growing fields. Fourteen F1 hybrid onion cultivars (Turbo,E-joeun, Premium gold, etc.) and two open-pollinated culti-vars (Changnyeongjunggo, Chunjujunggo) were intermediate-dayonions in bulb development, and mid or late maturing type in matu-rity. The onion seeds were sown from late August to mid September,transplanted from late October to early November at a plant den-sity of 33.3 ± 2.3 individuals m−2, and onion bulb were harvestedfrom 3 to 9 June, when 80–100% of the plant tops had broken overat the neck.