Effects of vermicompost and mycorrhizal fungus on quantitative and qualitative traits of medicinal plant Stevia rebaudiana Bertoni

In order to investigate the effect of vermicompost and mycorrhizal fertilizers on Stevia rebaudiana Bertoni, a factorial experiment was conducted in a completely randomized design with four replications in the research greenhouse of Agriculture College of Gonbad Kavous University in 2016-2017. The First factor was vermicompost at four levels (0, 10, 20 and 30 % of soil weight) and the second factor was inoculation with biological fertilizers at three levels (no inoculation (control) and inoculation with mycorrhizal fungi Glomus intraradieces and Glomus mosseae about 400 fungi spores per pot). The results showed that all cuttings were gradually eliminated in the treatments containing 30% vermicompost due to its high salinity, and had very low growth in treatments containing 20% vermicompost. The effect of vermicompost and mycorrhizal fungi on all traits studied, except the main effect of mycorrhizal fungi on the number of lateral branches and anthocyanins, were significant at 1% probability level. Also, their interaction was significant for all traits except stem dry weight. Based on the results, the highest positive effect was obtained in application of G. mosseae with 10% vermicompost for morphological traits such as plant height (126.63 cm) and root length (33.75 cm), and G. intraradieces with 10% vermicompost for flower (1.03 g) and root (9.93 g) dry weight and leaf area (78212 cm2) compared to no inoculation of mycorrhizal fungi at different levels of vermicompost. The highest content of chlorophylls a and b and total chlorophyll, and carotenoids (1.25‚ 1.58‚ 2.83 and 1.08 mg gr-1) was obtained in application of G. intraradieces with 10%vermicompost. The maximum content of soluble sugars (158.15 mg gr-1) was observed in 10%vermicompostwithout mycorrhizal inoculation treatment. According to the results of this study, the use of G. mosseae and G. intraradices fungi together with 10% vermicompost had the most positive effect on the quantitative and qualitative characteristics of Stevia rebaudiana.