Chemical and physical characteristics of wheat root mucilage influenced by <i>Serendipita indica</i> symbiosis: a comparison among four cultivars

Although there is evidence to suggest that the endophytic fungus Serendipita indica plays a crucial role in enhancing plant tolerance against biotic/abiotic stressors, less is known about the impacts of this symbiosis association on root mucilage chemical composition and its physical functions. The mucilage of inoculated and non-inoculated seedlings of four wheat cultivars (i.e., Roshan, Ghods, Kavir and Pishtaz) were extracted using an aeroponic method. Total solute concentration (TC_m), carbon content (C_mucilage), electrical conductivity (EC), pH, fatty acids, surface tension (σ_m), and viscosity (η_m) of mucilage were measured. Ghods and Kavir had the highest and lowest root colonization percents, respectively. Saturated fatty acids, including palmitic and stearic acids, were dominant over unsaturated fatty acids in wheat root mucilage. However, their compositions were significantly different among wheat cultivars. S. indica colonization, especially for Ghods, increased the TC_m, C_mucilage, and palmitic acid. Moreover, root mucilage of S. indica-inoculated Ghods had lower σ_m and greater η_m. An increased amount of powerful surfactants like palmitic acid in the mucilage of S. indica inoculated treatments led to lower σ_m and greater η_m. Such studies provide further support for the idea that plant-released mucilage plays a major role in modifying the physical environment of the rhizosphere. This knowledge toward truly understanding the rhizosphere can be potentially used for improving the rhizosphere soil quality and increasing crop growth and yield.