بررسی فعالیت آنتاگونیستی باکتری های جدا شده از رایزوسفر و بقایای گندم روی Xanthomonas translucens عامل لکه نواری گندم

Bacterial leaf streak disease caused by Xanthomonas translucens is an important disease of wheat that causes significant damage in Iran. In the past few decades, increasing awareness of the chemical pesticides treats on the environment and human health has led to the more attention to the use of biological pesticides. The present research was aimed to find antagonistic isolates against Xanthomonas translucens. In order to find antagonistic isolates, soil samples and plant residues of wheat fields were collected from Dezak region in Chaharmahal-o-Bakhtiari province and Borkhar region in Isfahan province. The epiphytic and soil bacteria were isolated and their antagonistic effect was studied by different methods including double layered agar plate, co-cultivation of pathogen and antagonist, culturing of antagonist isolates 24 hours prior of pathogen, use of culture filtrates and single layered agar plate. Based on the results, seven antagonistic isolates were chosen for investigation of their effectivity in greenhouse. In green house experiment, the wheat plants were inoculated at the six-leaf stage by spraying pathogen suspension. The treatments were applied at two times, one day prior and one day after of bacterial inoculation. The Oxytetracyclin solution and water were used as positive and negative control groups, respectively. Two weeks after inoculation, the diseases severity was measured using Duveiller pictorial diseases assessment key, in each replicate. Data were analyzed by SAS 9.1 software. The results indicated that antagonists significantly reduced the diseases severity. b4D isolate was the most effective isolate. The diseases severity in this treatment was less than tetracycline. The time of application had no significant effect. In this study, the laboratory results were consistent with the greenhouse outcomes. So that, the isolates that had inhibitory effect in the laboratory, were also effective in greenhouse conditions.