Occurrence of Wheat Take-all Disease Caused by Gaeumannomyces Graminis var. tritici in Zanjan Province and Evaluation of Inhibitory Effect of wheat Rhizosphere Bacteria on the Causal Agent of the Disease

Wheat root and crown rot known as take-all disease caused by Gaeumannomyces graminis var. tritici is one of the most important diseases of wheat worldwide. In Iran,the disease has been reported from provinces such as Markazi and Golestan. In recent years, symptoms of the disease such as stunted and yellow plant, rotted roots and whitened/empty heads have been observed in wheat fields in various areas of Zanjan province. This study was conducted to probe the existence of the disease in the province, to identify its causal agent and to identify wheat rhizobacteria for possible use in the biocontrol of the disease. To this aim, 25 samples were collected from wheat roots and soil surrounding them in various areas of the province. Fungi were isolated on potato dextrose agar (PDA) and identification of Ggt was performed based on CMI Description. Pathogenicity of fungal isolates was proved on wheat in the greenhouse. Isolation and identification of rhizobacteria were performed based on conventional procedures. From 420 bacterial isolates, 140 isolates were selected based on preliminary grouping and were screened for their antagonistic effects in the lab. Thirty-four isolates with the most inhibitory power were selected for identification by biochemical tests. Results showed that antagonistic bacteria mainly belonged to Pseudomonas, Erwinia and Bacillus genera. Finally, three strains representing the three genera were selected and their capability for the control of the disease was studied under greenhouse conditions. Results revealed that bacteria belonging to the mentioned genera can be used for biocontrol of the disease.