Plant growth regulators affecting in vitro cultivation of Stevia rebaudiana

Abstract

In order to maximize efficiency of plant propagation via direct organogenesis, the influence of plant growth regulators on the growth and development of Stevia rebaudiana grown in vitro was studied. Results indicated that benzyl adenine increased multiplication rate, vitrification and somaclonal variation. However, the best results were recorded with MS nutrient medium without plant growth regulators during in vitro growth and development of Stevia rebaudiana. MS basal medium supplemented with 2 mg/l BA recorded the highest number of shoots, but these shoots were very thin and vitrified and not suitable for multiplication through several subcultures. The nutrient medium (MS basal medium) supplemented with 10 mg/l kinetin recorded 45 shoots / explant as compared to MS nutrient medium which recorded 6.63 shoots / explant but growth parameters for Stevia rebaudiana plantlets grown in MS medium without kinetic is better than MS medium containing kinetin at high concentrations. Nutrient medium (MS basal medium) supplemented with IBA at low concentrations (0.01mg/l) or without auxins achieved the best in vitro growth of Stevia rebaudiana plantlets (100 % root formation). IBA was better than NAA and IAA for shoot and root formation. Increasing NAA concentrations decreased gradually number of shoots. Regarding the effect of NAA on root formation, data indicated that the per cent of shoots formed roots was 87% on MS basal medium without plant growth regulators as compared to MS basal medium supplemented with NAA at low concentrations 0.001, 0.01 and 0.1 mg/l NAA where root per cent was 80%, 73 % and 53 % respectively. On the other hand, NAA at 1.0 and 1.5 mg/l did not help shoots to form roots. Statistical analysis of variance showed no significant differences amongst IAA treatments for in vitro growth of plantlets. Stevia rebaudiana plants were adapted and grown well in planting media containing peat moss, sand and vermiculite at equal volume.