Optimization of Shoot Tip Culture of Carnation (Dianthus caryophyllus L.) Under In vitro Condition

Primary explant establishment is one of the most important steps in shoot tip culture that during this period، the percentage of vitrification is high that is due to small size of explant and therefore their amount of establishment is low. So in order to study of the effect of growth regulators and explant size on shoot tip culture of carnation، a factorial experiment was conducted in a completely randomized design (CRD) with 5 replications. Factors consisted of different size of shoot tip (0. 4، 0. 7 and 1 mm) and MS medium with different growth regulators (0. 5 mg benzyl adenine (BA)، 0. 5 mg gibberellic acid (GA3) and medium without hormone). The results showed that explant size and type of growth regulator had a significant effect on vitrification of explants and the highest amount of it (%59. 3) was observed on medium containing 0. 5 mg/l BA and explant size of 0. 4 mm and the lowest amount of it (%0) was occurred on medium supplemented with 0. 5 mg/l GA3 and explant size of 1 mm. Application of BA in the medium caused the reduction of plant height and increase in shoot dry weight، leaf width، number of regenerated shoots and leaf area index، but at the same time it leads to increasing the vitrification and thus the quality of plants reduced. While use of GA3 in the medium increased plant height، leaf length and decreased leaf width and grown plants were apparently healthy. In the medium without hormones، grown shoots did not show normal growth and after a while their growth stopped. During establishment period of shoot tip، the quality of plantlet is so important for micropropagarion stage and during this period the numbers of regenerated shoots are not so important. Therefore، medium containing 0. 5 mg/l GA3 for explant with the size of 1 mm is recommended.