Role of endomycorrhizae and Pseudomonas fluorescens on the acclimatization of micropropagated Stevia rebaudiana Bert. plantlets

Stevia rebaudiana Bert. is a non-caloric sweetener plant of medicinal and commercial values. This study was performed to micropropagate Stevia and improve its ability to withstand the sudden shocks of the environmental changes during acclimatization by using endomycorrhizae and/or Pseudomonas fluorescens. In vitro establishment of Stevia was superior by culturing shoot tips and nodal segments of mature plants on Murashige and Skoog medium supplemented with 0.5 mg/l 6-benzyl adenine and 1 mg/l β-naphthalene acetic acid, and nodal segments gave better response when compared to shoot tips. While 6-benzyl adenine alone at 1 mg/l was found to be the most promising concentration for shoots multiplication for four successive subculturing. The best rooting response was obtained on half strength Murashige and Skoog medium supplemented with 1 mg/l β-naphthalene acetic acid. Adding 8 ml/l mycorrhizal root extract gave 100% rooting with the highest mean number and length of roots and shoot height. Inoculation of plantlets with endomycorrhizal spores alone in non-sterilized soil increased the survival percentage to 90% and gave the highest mean number and length of both shoots and roots, as well as leaves number. Moreover, they recorded the highest values of total chlorophyll, NPK and relative water contents. Key words: Stevia, micropropagation, mycorrhizae, mycorrhization helper bacteria.