Effect of vernalization period and bulb size on bolting of onion cultivar “Texas Early Grano” grown under Gezira conditions, Sudan

Elfatih A.M. Elsiddig, Osman M. Elamin, Mohamed E. Elkashif


Texas Early Grano onion cultivar is very popular in Sudan and is used mainly as a salad vegetable. Unfortunately, this cultivar does not flower and produce seeds under Sudan conditions and seeds should be imported from abroad. Attempts to produce seeds of this cultivar under Gezira conditions have failed. Therefore, the objective of this research was to study the effects of bulb size and vernalization on the induction of flowering of Texas Early Grano onion cultivar. Experiments were conducted at the research farm of the Faculty of Agricultural Sciences, University of Gezira, Wad Medani, Sudan, during the  winter seasons of 2008/09 and 2009/10.   Treatments consisted of vernalization periods ranging from 45 to 180 days, storage temperatures of 4 to 50C, and bulb size which was small and medium. Treatments were arranged in a  randomized complete block design with three replicates. Results indicated that vernalization duration significantly affected emergence percentage. As vernalization duration increased, emergence percentage increased in both seasons. Bulb size had no significant effects on emergence percentage. Vernalization temperatures of 4 to 50C for 90 days or more was the key factor for the induction of bolting of Texas Early Grano cultivar. To obtain the highest bolting percentage and seed yield, a combination of venrnalization at 4 to 50C for 180 days and medium-sized bulbs should be recommended.


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