تأثیر میکروارگانیزم‌های آنتاگونیست خاک‌های شالیزار گیلان روی عامل بیماری پوسیدگی طوقه برنج

One hundred and two microorganisms were isolated from 85 paddy soil samples of different locations in Guilan Province. Antagonistic effects of the microorganisms were tested against Gibberella fujikuroi on PDA medium. Twenty one microorganism isolates were selected for seed treatment in blotter test. Seven isolates that were satisfactorily effective in reducing pathogen colonies formed on seeds and seedlings were tested in controlling disease in a greenhouse experiment with split plot design. The antagonists were Bacillus subtilis, B. circulans, Bacillus sp., Trichoderma harzianum, T. virens (2 isolates), and F.23 (unidentified). Results showed that all antagonists effectively reduced the disease in sterilized soil compared with control but overall effectiveness of B. subtilis, T. harzianum, and T. virens was higher than others and lower than the fungicide treatment (thiophant methyl thiram W.P. 80% , 2g/L). It was found that when seeds were treated with antagonists prior to inoculation with the pathogen, the effectiveness of antagonists was significantly better than when they were applied after seed infection with the pathogen.