The effects of several carbohydrates-glycerol, sorbitol, mannitol, lactose, glucose, and galactose were studied at different concentration ranges (1-5%) on embryogenesis of ovule-derived calli from three species and four varieties of Citrus; Clementine mandarin (Citrus clementina), Washington Navel orange (C. sinensis), Kutdiken and Zagara Bianca lemon (C. limon). The best results of embryo formation from calli of different citrus varieties were obtained in 4% and 5% glycerol concentrations. Sixty-seven Washington Navel orange embryos and 137 Zagara Bianca lemon embryos were obtained at a concentration of 4% glycerol. Clementine mandarin and Kutdiken lemon produced significant numbers of embryos-808 and 453, respectively, at the concentration of 5% glycerol. Embryogenesis was also stimulated at fewer rates with other carbohydrates, such as lactose and sorbitol, at the various concentrations in all utilized citrus calli in this study. (c) 2006 Elsevier B.V. All rights reserved.