The Effect of Arbuscular Mycorrhizal Fungi and Drought Stress on Some Physical and Mechanical Characteristics and Soil glomalin Content on Blue Panic Grass (Panicum antidotal

Background and objectives: A lot of arid and semi-arid deserts comprise sandy hills. The major problems in these coarse-textured soils including low organic compounds, high percentage of sand and unstable aggregates, have led to restricted use of these soils. Arbuscular mycorrhizal fungi by secreting a glycoprotein called glomalin, has a significant role at improving soil structure and aggregate resistance. These fungi enhance tolerance of plants to environmental stresses by increasing plant resistance in desert lands which leads to a better establishment in this area. The aim of the present study was to investigate the impact of arbuscular mycorrhizal fungi symbiosis to improve the physical and mechanical properties and glomalin content of sandy loam soil under cultivation of blue panic grass and drought stress.
Materials and methods: In order to examine the effect of different levels of moisture [irrigation at 80% (Control, S1), 50%(S2) and 20% of field capacity (S3) ] and inoculation of arbuscular mycorrhizal fungi [Control(NM), Glomus mosseae (GM), Glomus intraradices (GI) and simultaneous inoculation of both fungi (MI)]. An experiment as factorial in completely randomized design was conducted. The rhizomes has been cultivated in pot contains 8Kg of soil after adding inoculant at depth of 5cm of soil and kept 3 months at relatively controlled condition. At the end of the experiment root colonization percentage and qualitiy and quantity of glomalin bulk density, shear resistance, pentration resistance and aggregate stability by dry sieving method were measured.
Results: Mycorrhizal symbiosis and drought stress significantly increased glomalin content of the soil. Protein bands on polyacrylamide gel demonstrated more expression of the glycoprotein under stress as a defense mechanism to drought. Root colonization was significantly reduced under drought stress and remarkably increased by mycorrhizal symbiosis. The effect of simultaneous treatments proved to be efficient on shear stress of soil. The aggregate stability increased by increasing moisture content of soil and application arboscular mycorrhiza fungi, but interaction of fungi and moisture level was not significant on bulk density and penetration resistance of soil. Soil bulk density reduced in the mycorrhizal treatments by increasing soil moisture content.
Conclusion: Mycorrhizal symbiosis reduced the negative effects of drought stress in the soil. The obtained results showed more efficiency of Glomus intraradices to decrease negative effect of drought on soil proportion than Glomus mosseae. Arboscular Mycorrhizal fungi can help to reduce soil erosion by improving plant growth, soil physical and mechanical characteristics by glomalin secretion increament.