Mycorrhizal Fungi and Thiobacillus Co-inoculation Improve the Physiological Indices of Lallemantia iberica Under Salinity Stress

Salinity, a serious environmental pressure on crop production, might be counteracted by free-living and symbiotic inoculants entailing positive synergistic effects. Enhancement in nutrient uptake and/or production of antioxidants under the stress condition, can improve plant growth and yield. In this study, inoculation of Lallemantia iberica with Funneliformis mosseae and the sulfur solubilizing bacterium (Thiobacillus sp. T95 and T40) was evaluated under two salinity levels (6.72 dS/m and 0.91 dS/m as control). The root colonization, spore density, seed and biological yield, total soluble sugars, and nutrients were reduced by salt stress. Antioxidant enzyme activity (catalase, superoxide dismutase, peroxidase and ascorbate peroxidase), proline, contents of sodium and sulfur have increased under salt stress. The enzyme activities as well as the concentrations of nitrogen, phosphorus, potassium, sodium, and sulfur were dropped at the flowering stage (75 days after sowing). Seed and biological yield, antioxidant enzymes activity, proline content, and nutrients were significantly improved in mycorrhizal treatments. Inoculation of Thiobacillus exhibited the positive effect on root colonization, spore density, enzymes activity, and nutrients. Bacterial treatments (dual and single) significantly increased the sulfur and total soluble sugars. Totally, the mycorrhizal plants accumulated more enzymatically produced antioxidants, osmolytes, and showed improved nutrient uptake. Our results provide new insights into the relationship among arbuscular mycorrhizal fungi (AMF), biosulfur bacteria, and plant growth under saline conditions. In conclusion, the Lallemantia iberica inoculation with mycorrhizal fungi, either alone, or in combination with Thiobacillus, is indicated for optimum plant yield through alleviation of the salinity stress.