Evaluation of antimicrobial activity of some biological compounds containing Bacillus subtilis to control of cotton seedling damping-off caused by Fusarium solani

Fusarium solani is one of the most important agents to cause cotton seedling damping-off. The best method to control this disease is the seed coating with chemical fungicides and biological compounds. In this research, the purpose was to replace biological compounds containing Bacillus subtilis with chemical pesticides. Biological commercial products (Super nitro plus, Biosubtil, and Companion) were evaluated in this study. The results showed that the purified B. subtilis isolates from Biosubtil, Companion, and the native isolate B96 had the most inhibition percentage of F. solani growth by 46.67%, 44.67%, and 41.67%, respectively in dual-culture test. Also, the purified B. subtilis isolates from Biosubtil and Super nitro plus showed the highest inhibition percentage of F. solani growth in volatil compounds test by 12.77 and 10.19 %, respectively. Among the investigated fungicides, Carboxin Thiram with 49.06% had the highest and Imazalil (Fungaflor 5%) with 9.91% had the least effect on mycelium growth inhibition of F. solani. In the greenhouse studies, Varamin cottonseed was treated with three different concentrations of each biological compound, suspension isolates B96 and Carboxin Thiram (75%WP), Triadimenol (7.5%DS), Iprodione-Carbendazim (52.5%WP), Imazalil, and then they planted in the contaminated soil with the pathogen. Biosubtil was the most effective treatment for the control of seeding damping-off in cotton and this compound was equivalent to Carboxin Thiram for disease control. The results showed that the possibility of replacing common chemical pesticides with some biological compounds for cottonseeds treatment.