Effect of carbon sources on biocontrol efficiency of Bacillus pumilus INR7

Plant growth promoting (PGP) bacteria not only improve plant growth and yield but also increase plant resistance to biotic and abiotic stresses. Culture design in fermentation process has critical effect on biomass production and efficacy of these bacteria. In this work, effect of some of carbon sources have been investigated on biomass production and efficacy of Bacillus pumilus against Rhizoctonia solani, the causal agent of bean damping-off. Effect of carbon sources, glucose, molasses, brown sugar, corn meal and rice meal, in three concentrations have been examined on B. pumilus INR7 biomass production and suppression on bean damping-off in greenhouse. The highest biomass production achieved in 20 g/L of glucose and brown sugar, respectively. Increasing glucose concentration decreased biomass production but enhanced plant growth factors and the highest plant growth have been recorded in 40 g/L as the highest concentration of glucose. Molasses also increased PGP efficiency at its mid concentration, 20 ml/l. Effect of carbon sources on biocontrol efficacy of B. pumilus INR7 exhibited that glucose at 40 g/L led to the lowest root and crown infection. Molasses in 20 and 40 ml/l showed noticeable effect on biocontrol efficacy of B. pumilus INR7. In conclusion, glucose and molasses had highest effect on biomass production and biocontrol efficacy of B. pumilus INR7.