Study on the role of some inorganic and organic carriers in the efficacy of bacterial antagonists in controlling sugar beet seed rot and seedling damping-off disease

The easiest and the most practical application method of biocontrol agents in the field is the use of powdery formulations which can be used by farmers as seed treatment particularly in controlling seed and root diseases. In this study, the possibility of development of some new bioformulations using antagonistic bacteria and some organic and inorganic carriers was investigsted. Two antagonistic bacterial isolates belonged to Pseudomonas fluorescens and Bacillus coagulans which have performed efficiently in preleminary studeis were selected and 8 biofomulations were developed and prepared using 4 inorganic and organic carriers including Talc, Bentonite, Rice bran and Peat. For preparation of bioformulations, bacterial suspension (109 cfu ml-1) were mixed with powdery carriers and carboxy methyl cellulose (CMC) as the adhesive compound. The role of carriers in the efficacy of bacterial antagonists in controlling Rhizoctonia solani-induced sugar beet seedling damping-off were then evaluated in the green house condition 15, 30 and 45 days after sowing. Results indicated that some of bioformulations were as or more effective than carboxin-thiram in reducing sugar beet seedlings damping-off disease. According to the results, treatments contained peat and rice bran with both bacterial isolates and Talc with P. fluorescens were the most effective and caused a significant reduction in disease severity. In statistical analysis of the results, these treatments were placed in different groups compared with untreated control and carboxinthiram, the commonly used fungicide. In addition to the disease controlling effects of bioformulations, their effectiveness in promotion of some growth characteristics of sugar beet including seedling height, seedling root length, seedling fresh weight and seedling dry weight were also evaluated. The results indicated that most of the developed bioformulations performed well and significantly promoted sugar beet seedlings growth characteristics. In this section, the treatments containing peat, talc and rice bran with both bacterial isolates, were the most effective which increased sugar beet seedlings growth characteristics significantly in comparison with the untreated control. The overall results of this study indicate that it may be possible to prepare some new bioformulations using bacterial antagonists and inorganic or organic carriers. This bioformulations may be used as seed treatments in the sugar beet fields for controlling seedling damping-off disease and promoting seedlings growth characteristics.