Effect of water deficit and inoculation with symbiotic micro-organisms on traits of phenological, morphological, agronomic and qualitative properties in soybean

Drought stress is one of the important factors of abiotic stress that affects plant growth and yield. Soybean crops are used in most parts of the world to produce oils, vegetable proteins and forages. In sustainable agricultural systems, the use of biofertilizers is of particular importance in increasing plant production and soil fertility. Fungi improve the growth, development and function of host plants in agricultural systems by creating a symbiotic relationship with plant roots by increasing water absorption, increasing resistance to live stress (pathogenic) and abiotic (drought and salinity) stresses. Therefore, this study was conducted to investigate the effects of water deficit on important crop characteristics, seed yield and oil and protein harvest index of soybean cultivar Kosar under conditions of inoculation with arbuscular mycorrhizal and rhizobium bacteria in Urmia. Experiment was conducted as factorial split plot based on Randomized Complete Block Design with three replications at Research Farm of Agricultural highschool of Urmia during 2017. The main factor was three levels of irrigation (irrigation after 70 mm evaporation), moderate stress (irrigation after 110 mm evaporation) and severe drought stress (irrigation after 150 mm evaporation from class A evaporation pan), subplots were including mycorrhizal fungus in three levels of none inoculation, Glomus mosseae, Glomus intraradices and Risobium bacteria in two levels, none inoculationand inoculation with Rhizobium japonicum.. . In severe drought stress compared to optimum irrigation conditions, leaf area index, stem diameter, plant height and seed yield were significantly decreased 60, 31, 11 and 22 percent, respectively. In all irrigation conditions, inoculation with mycorrhiza G. mosseae and G. intraradices in comparison to non-inoculation, plant height, stem diameter, oil and protein harvest index, leaf area index and seed yield increased, but reduced proline. In optimum irrigation, mild and severe drought stress conditions, inoculation with bacteria in comparison to non-inoculation with bacteria, increased seed yield about 17, 19 and 17 percent, respectively. Inoculation with G. mosseae and G. intraradices in comparison to non-inoculation of mycorrhiza increased seed yield about 13% and 8%, respectively. The highest percentage of root colonization was obtained from G. mosseae (48.80). Inoculation with bacteria compared to non-inoculation increased the percentage of root colonization about 17%. Inoculation with bacteria compared to non-inoculation increased the nitrogen percentage about 8%. Moderate drought stress led to increase nitrogen content. Drought stress was decreased significantly phenological traits such as growth period and time to flowering, morphological traits such as stem diameter, pod length and plant height, qualitative traits such as nitrogen percentage and yield, oil harvest index, physiological traits such as leaf area index, seed yield and root colonization of Kowsar cultivar, while led to increase the proline content. Inoculation with Mycorrhiza fungus especially Glomus mosseae and inoculation with Rhizobium increased the access to water and nutrients and increased all traits in this study. It also reduced proline in all three irrigation conditions and ultimately increased seed yield. Thus, by inoculation of mycorrhiza fungi, in particular G. mosseae and Rhizobium japonicum bacteria, it was possible to obtain suitable conditions for obtaining maximum quantitative and qualitative yield in soybean plants under different moisture conditions. in addition to reducing the effects of drought stress, also reduced the use of chemical fertilizers.