To study the impact of Mycorrhizal fungus on flue-cured Virginia tobacco (K326) an experiment was carried out in the Golestan Province of Iran in 2014. The experiment was performed as a complete randomised block design with four replications, the factors studied included four different levels of Mycorrhizal Fungus (Glomus spp include: Mosseae, Intraradices and Etunicatum) inoculum as follows: 0, 6, 12 and 18 grams with 100 propagules/g. Inoculum was applied at the sowing stage in the float system per cell in seed trays.

The results indicated that Mycorrhizal inoculation had a significant positive effect on the measured characteristics. In the cases of sugar, leaf size, total wet and dry weights of tobacco leaf, there was a significant difference between treatments. In the case of total crop value and the chlorine levels, there were significant differences between treatments. There was no significant change in nicotine content. The maximum tobacco wet and dry weights were 22745 kg/ha and 3218 kg/ha respectively, with 18 g of Mycorrhizal inoculum. By increasing the amount of mycorrhizal inoculum, the sugar and chlorine levels were increased. 18 g of mycorrhizal inoculum made the highest meaningful difference in the sugar level, at 12.8%, compared with 6.15% in the control. Results showed that through increasing the fungi level, the sugar level increases in the leaves showing that the fungi have a positive effect on tobacco. The effect of fungi on the chlorine level was also significant and the highest level of chlorine (mean 5.7%) was achieved with 18 g of mycorrhizal inoculum, and the control treatment had the lowest chlorine level. Considering the total crop value, it can be concluded that with mycorrhizal inoculation, the total crop value increased and the highest increase of 32% per hectare was achieved with 12 g of mycorrhizal inoculum; in other words, using 12 g of mycorrhizal inoculum increased the tobacco dry and wet weights, the leaf quality, the leaf size and the leaf colour. Using mycorrhizal fungus decreased leaf length, with the longest leaf (40.89 cm) achieved by the control treatment and the shortest with 18 g of mycorrhizal treatment.