Abstract
Carnation (Dianthus caryophyllus L.) is the third most important cut flowers in the world. Tissue culture techniques offer an efficient method for micropropagation of this ornamental plant. In present work effects of Kinetin (Kin) and Benzyl Adenine (BA), on shoot multiplication and hyperhydricity of four carnation cultivars (Prado Aquila Kgr, Skimo Mogr, Mondeo Kgr and Innove Orange Bogr) were studied. Explants from nodal segments were cultured on MS medium supplemented with different concentrations of BA (1, 2, 3 and 4 mg/l) and Kin (1, 2, 3 and 4 mg/l) in combination with 0.2 mg/l NAA, 30 g/l sucrose and 8 g/l agar. Rooting of regenerated shoots was done in the MS medium supplemented with 1 mg/l NAA. Results indicated that there is a significant difference among cultivars shoot regeneration, Eskimo and Prado Aquila Kgr with 3.2 and 1.5 shoots show the highest and lowest regeneration rate, respectively. Increasing the concentration of cytokinin from 1 mg/l to 4 mg/l lead to increase regenerated shoot number from 1.7 to 2.4 shoots per explant and increase hyperhydricity from 12% to 54%. In addition high concentration of cytokinin, especially BA, decreased height of regenerated shoots. Based on hyperhydricity percentage of regenerated shoots, there was a significant difference between cultivars and cytokinins. Mondeo Kgr and Prado Aquila Kgr showed highest (44%) and lowest (23%) hyperhydricity, respectively and explants cultured in medium supplemented with BA caused more (40%) hyperhydricity than Kin (26%). Results of present work showed that by increasing the concentration of cytokinin specially BA, multiplication will be increased but also it will increase the hyperhydricity of plantlets and consequently it will lead to death of them. By considering the amount of multiplication and frequency of hyperhydricity for obtaining the highest number of normal shoots, using of MS medium containing 1 mg/l BA in combination with 0.2 mg/l NAA is suggested.

Keywords: Carnation, Benzyl Adenine, Kinetin, Hyperhydricity, Shoot multiplication, Micropropagation