development of new bioformulations of pseudomonas fluorescens and evaluation of these products against dampingoff of cotton seedlings
S.S. Ardakani, A. Heydari, N. Khorasani, R. Arjmandi
There is growing interest in the use of biological approaches to replace chemicals in fertilizing soils or improving plant resistance against phytopathogens. In this regard plant growth promoting rhizobacteria (PGPR) have a potential role. In search of efficient PGPR strains with multiple activities, we prepared eight new bioformulations using two strains of Pseudomonas fluorescens isolated from different rhizosphere soils and plant roots in the Iranian cotton fields. Formulations included a talc-based powder and bentonite-based powder as mineral carriers and peat and rice bran as organic carriers for increasing stability in interaction between PGPR and cotton plants. The results of a greenhouse experiment, where these products were applied to cotton seeds at intervals of 15, 30, 45 and 60 days after sowing to control seedling damping-off, showed that all treatments except TAL-B2 were effective (up to 62.5% control) as compared to untreated seeds. The efficacy of BENT-B1, PT-B1 and PT-B2 treatments was much higher (between 1.42 to 1.92 fold) than that of the standard carboxin-thiram fungicide treatment at all stages. Our results indicate that organic and inorganic carriers may efficiently be used for improving the stability and effectiveness of biocontrol-active microorganisms in controlling plant diseases.