Suppression of wheat take-all (Gaeumannomyces tritici) using a combination of Bacillus subtilis GB03 and several important nutrients in soil

Take-all disease caused by Gaeumannomyces tritici is an important crown and root rot disease of wheat throughout the world. In this work, a combination of fertilizers and Bacillus subtilis GB03 were examined on wheat growth and percentage of the infected root. Soil physical and chemical properties have been analyzed in the first step. Different concentrations of nitrogen, phosphorous, Fe, Zn, and Cu have been selected based on soil analysis data and literature review. The effect of combining bacteria and fertilizers was tested in a greenhouse for 35 days. The bacteria was applied as seed bacterization and post-planting drench. Among fertilizers, Phosphorus showed the greatest effect on control of this disease. Triple superphosphate linearly reduced the percentage of root infection to 51.14%. Bacteria enhanced inhibition activity of phosphorus by 71.50%; so that the symptoms on crown have been eliminated even at the lowest levels of fertilizer (25 mg per kg of soil). The lowest level of Nitrogen (50 mg urea/Kg of soil) reduced root infection percent up to 35%. Iron fertilizer had an outstanding effect on disease inhibition and reduced the disease from 60.5 to 46% in its lowest level (1.3 mg/Kg of soil). A combination of bacteria and the second level of Zn concentration decreased disease symptoms, significantly. Cu fertilizer decreased disease symptoms to 18.4%. Its effect was significant in more than 5 mg/Kg of soil. This fertilizer improved growth factors in combination with bacteria. In conclusion, the effect of nutrients was dependent on their availability in tested soil.