Evaluation of eps E gene expression and the role of the exopolysaccharide of Bacillus amyloliquefaciens in the control of wheat take-all

Plant growth–promoting rhizobacteria (PGPR) release polysaccharides extracellularly into the environment called exopolysaccharides in the form of capsules or slime, protecting them from biotic and abiotic stress conditions and enabling them to survive in the rhizosphere. Bacillus amyloliquefaciens is well known for producing wide spectrum of biopolymers and antimicrobial compounds.  On the other hand, take–all is one of the most important diseases of wheat caused by the fungus Gaeumannomyces graminis var. tritici. Biological control of this disease depends on the colonization of bacterial population in rhizosphere under stress conditions. In present study we targeted one of the most important genes in the production of exopolysaccharide polymer called eps E gene showed that bacterium has. The eps E gene expression analysis by Real Time PCR technique showed that bacteria in the treatment of culture medium prepared with sucrose and glucose compared with the control treatment had a 60–fold increase in eps E expression. The results of disease control showed that there was a significant difference in the disease incidence when seeds were treated with bacterium plus the maximum exopolysaccharide and bacterium with minimum exopolysaccharide, in comparison with a control treatment. The percentage disease inhibition recorded for the treatments of Baran cultivar 88 and 64% and Ouhadi cultivar 88 and 56% related to culture medium containing EPS with maximum amount and nutrient broth culture medium with minimum amount of EPS, respectively. The overall results of this study demonstrated that the B. amyloliquefaciens with high production of exopolysaccharide had a strong ability to control take–all disease in comparison with treatment of NB culture medium.