Effect of Explants Type and Plant Growth Regulators on the Initiation and Multiplication of Vegetative Shoots of Stevia rebaudiana Bertoni in vitro

Abstract

This study was carried out in the Plant Tissue Culture Laboratory of the College of Agriculture - Karbala Unaiversity for the period from 2022 to 2023. The study included the use of explants and different combinations in the sterilization, initiation and multiplication of the vegetative shoots of the Stevia plantiv vitro, the study was carried out in three phases: the first included sterilization of explants (shoot tips and lateral buds) using sodium hypochlorite at concentrations of (0, 0.5, 1, 1.5, 2)% for periods of (5, 10, 15) minutes. The second included the initiation of shoots cultures by cultivating the shoot tips and lateral buds on the MS medium with different concentrations (0, 0.5, 1, 1.5) mg l-1 BA and (0, 0.1, 0.2, 0.3) mg l -1 NAA, the third stage was carried out by cultivating the growths resulting from the shoot tips cultivated in the previous stage on the MS medium prepared with different concentrations (0, 1, 2, 3, 4) mg l-1 BA and (0, 0.1, 0.2, 0.3, 0.4) mg l-1NAA. The results of the study showed the superiority of the developing apical in achieving the lowest contamination rate of 38% compared to the side buds that achieved a contamination rate of 40.67%, and the concentration of 2% of NaOCl achieved the lowest pollution rate of 8.33%, and the duration of 15 minutes achieved the lowest pollution rate of 24%. The results of the initiation experiment showed the superiority of the shoot apical as a explants that achieved the highest response rate to emergence of 70% compared to the lateral shoots that recorded a response rate of 54.69%, and the concentration of 1 mg l-1 BA was significantly superior and achieved a response rate of 82.5% compared to the comparison treatment that gave a rate of 82.5%. A response of 32.5%. As for the results of the vegetative multiplication experiment, the results showed the superiority of BA at a concentration of 3 mg l-1 in achieving the highest rate in the number and length of branches was 33.35 branches Plant-1, 8.20 cm respectively. compared to the comparison treatment that achieved the lowest rate, and the concentration of 0.3 mg l-1 NAA was superior in achieving the highest average of the number and length of the vegetative total reached 30.84 plant branch-1, 7.65 cm respectively, while the comparison treatment achieved the lowest mean for the studied traits.