The effect of Piriformospora indica inoculation on salt and drought stress tolerance in Stevia rebaudiana under in vitro conditions

In order to investigate the effect of Piriformospora indica under salt and drought stresses on some vegetative characteristics and physiological parameters of stevia (Stevia rebaudiana Bertoni) medicinal plant, an experiment was conducted in factorial arrangement based on completely randomized design with three replicates at Genetics and Agricultural Biotechnology Institute in Sari Agricultural Sciences and Natural Resources University. Factors include three levels of osmatic potential (0, -5, and -10 bar) and with three osmotic sources including NaCl (Na), Mannitol (M) and NaClㆩ� (N) and inoculation of mycorrhizae like fungi at two levels (non-inoculated and inoculation with fungi). The plantlets were treated for 30 days and then some morphological and physiological parameters were measured. Results of ANOVA showed that there was a significant interaction between osmatic source and levels with fungi inoculation for the most determined parameters. Inoculation of stevia plantlets with P. indica at osmatic level of -5 bar caused either by M or M markedly improved dry weight of leaf (112 and 156%, respectively) and aerial parts (49 and 144%, respectively) as compared to the uninoculated control. Fungi inoculation positively improved vegetative parameters of stevia plant under most osmatic levels and sources. The most ameliorate effect, however, was observed where M as drought stress or M were adjusted to -5 bar. Therefore, the results of this study represented a positive effect of P. indica inoculation in inproving osmotic tolerance of stevia medicinal plant.