IDENTIFICATION AND ASSESSMENT OF POTENTIAL BIOLOGICAL CONTROL OF SUGAR BEET RHIZOSPHERIC BACTERIA ON RHIZOCTONIA CROWN AND ROOT ROT DISEASE

Background and Aim:Rhizoctonia crown and root rot of sugar beet occurs by soil born multi nucleus fungi Rhizoctonia solani (Thanatephorus cucumeris ( A. B. Frank) Donk.Methods:In order to investigate potential biocontrol of the disease by rhizospheric bacteria, infected sugar beet samples were collected from southern area of West Azerbaijan province and disease causal agent were isolated, purified and identified. Also in order to isolation and identification of sugar beet rhizospheric bacteria healthy sugar beet samples were taken from Mahabad, Bokan, Miandoab and Piranshahr cities. Suspension of rhizosphere soil serially diluted and cultured on NA medium. To screening and assessment potential antagonistic ability of bacterial strains, dual culture test between bacterial strains and pathogen were conducted on plates containing PDA+NA media sealed with plastic wraps.Results:After few days inhibitory zone diameters were measured. Among 71 isolates, 26 had inhibitory zone. 10 bacteria with more zones were selected for biochemical and physiological tests and phenotypic characterization were determined. On this basis, H12 isolate identified as Enterobacter sp. B11, D7 and T4 isolates identified as Pseudomonas putida. D13, D3, D2, H18, H20 isolates identified as Pseudomonas flourescens and M4 identified as Pseudomonas flourescens bv.5.Conclusion:Microorganisms living in rhizosphere of plants are suitable candidates for biological control and bacteria are the main member of root colonizing microbial population. Identified strains are belong to Pseudomonadaceae and Enterobacteriaceae families that found in any habitats and tolerable to different environments. The strains had good result in case of biological control of disease in vitro condition.

کلیدواژه ها:

Biological control ، Rhizosphere ، bacteria ، soil born