Study on the effect of some inorganic and organic compounds on survival of bacterial antagonists and their efficacy in controlling cotton seedling damping-off disease.

The extensive use of chemical pesticides in agriculture has caused numerous problems particularly in term of health and environment and has resulted in criticism by environmental protection agencies and the public. Due to the above mentioned issues, the search for alternative strategies for replacement or reduction of chemical pesticides has become extremely important. Biological control of plant diseases using fungal and bacterial antagonists has been accepted as a viable alternative for harmful chemical pesticides. One of the most important limiting factors in the use of biocontrol active microorganisms is the lack of efficacy in the field due to improper formulation. In this study, the possibility of development of some new formulations of biofungicides was investigated. Two antagonistic bacterial isolates belonged to Pseudomonas fluorescense and Bacillus coagulans which have performed efficiently in preleminary studeis were selected and 8 biofungicides were developed and prepared using 4 inorganic and organic carriers including Talc, Bentonite, Rice bran and Peat. The formulations were developed and prepared following the procedures described in the literature. In another part of the study, these formulations were used against Rhizoctonia solani the causal agent of cotton seedling damping-off which is considered to be one of the most important diseases of cotton. The efficacy of biofungicides was evaluated based on the number of healthy cotton seedlings in different treatments 15, 30 and 45 days after sowing. Results indicated that 5 out of 8 formulations were effective in controlling cotton seedling damping-off disease. The most effective biofungicides were Peat-B1, Peat-B2, RB-B1, RB-B2 and Bent-B1 which resulted in significant reduction in cotton seedling damping-off disease (compared with the control) and were as effective as Carboxin-thiram, the common fungicide which is being used for chemical control of this disease. The results of this study are promising and the developed biofungicides may be used for replacement of chemical fungicides in controlling cotton seedling damping-off and other plant diseases and result in the reduction of environmental contamination for approaching a sustainable agricultural system.