WINTER ONION SUSCEPTIBILITY TO PREMATURE BOLTING DEPENDING ON THE VARIETY AND THE SOWING DATE

The introduced onion cultivars into Republic of Macedonia, especially winter cultivars, have started to take an important place in the early vegetable production. However, each new cultivar has its biological specifics that can manifest (such as premature bolting) in some complex of ecological circumstances and reduce the production quality and quantity. In order to make a complete approach towards the above-mentioned issue of bolting, the trials have been set in three regions, on different sea levels (150 m, 250 m and 700 m) and corresponding climatic conditions. In each of the regions, the trials were organized in three sowing dates: October 10, October 25 and November 10. Four onion cultivars have been sown, out of which three are introduced (Aldobo, Julio and Ranger with yellow skin) and one is locally bred cultivar - Sidra. Based on the obtained results the recommendations for cultivar and sowing dates have been drawn, for each region. Aldobo and Julio have developed lower leaf mass compared to Sidra and Ranger. In respect of the appearance of bolting, Sidra bolts moderately, Aldobo and Julio very seldom, and Ranger has the largest percentage of bolting. Consequently, the yield and the quality production of the Ranger cultivar had been considerably reduced. In the later sowing dates, it was recorded that the percentage of bolting was reduced.