Physiological and biochemical responses of Mexican marigold (Tagetes minuta L.) to mycorrhizal fungi application under salinity stress condition

In order to investigate the effect of mycorrhizal fungi under salinity stress conditions on physiological and biochemical properties of Mexican marigold (Tagetes minuta L.), a pot factorial experiment was conducted based on a completely randomized design with two factors and three replications. The first factor was the application of two types of mycorrhizal fungi at three levels (non-inoculation, Rhizophagus intradices, and Funnetiformis mosseae) and the second factor was irrigation with salinity water at 4 levels (0, 40, 80, and 120 mM equal to 0, 3.5, 7, and 10.5 ds/m sodium chloride, respectively). The salinity treatment was applied in the plants at the eight-leaf stage and on three days a week. Results showed that application of salinity stress reduced the relative water content and chlorophyll of leaves. With increasing salinity concentration, the amount of electrolyte leakage, total carbohydrate, and proline increased in leafs. In contrast, the use of mycorrhizal fungi resulted in improved traits measured under salt stress conditions. The amount of proline, total carbohydrate, and electrolyte leakage decreased with the use of mycorrhizal fungi under stress conditions due to the positive effect of these fungi on balancing growth conditions in the plant under salt stress. Also, the highest amount of relative water content and chlorophyll a, b, and total chlorophyll of leaves were observed under non salinity stress treatment and application of R. intradices. According to the results of this research, it can be concluded that the application of salinity stress at 120 mM resulted in a significant reduction in the studied traits. Besides, the application of mycorrhiza fungi at this level of salinity could not improve the negative effects of salt stress. The use of R. intradices compared to the F. mosseae had a greater effect on the improvement of physiological and biochemical characteristics of Mexican marigold under salinity stress conditions at low salt concentration.