Trichoderma asperellum, an inoculant for the production of steviol glycosides in Stevia rebaudiana Bertoni plants micropropagated in a temporary immersion bioreactor

Stevia rebaudiana is a plant that synthesizes steviol glycosides, compounds with sweetening properties. The aim of this work was to establish a system for the micropropagation of S. rebaudiana plants in a temporary immersion bioreactor (TIB) and evaluate the effect of inoculation with Trichoderma asperellum of the micropropagated plants on the plant growth and the accumulation of steviol glycosides and phenolic compounds in leaves. S. rebaudiana plants with intact roots were propagated in the TIB with Murashige and Skoog medium and 0.37 mg L^-1 indolebutyric acid; subsequently, the plants were inoculated with spores of T. asperellum (4 ×10⁴ spores mL^-1). The plants propagated and inoculated with the fungus exhibited growth significantly larger than that of the uninoculated plants (control). The inoculated plants produced three-fold more steviol glycosides than the uninoculated plants (control), while the phenolic compound contents the inoculated and uninoculated plants were similar. These results encourage the possibility of using a TIB and T. asperellum for the propagation and growth promotion of S. rebaudiana plants with high steviol glycoside contents.