بررسی توانایی تجزیه تولاسین تولیدی توسط باکتری عامل بیماری لکه قهوه‌ای کلاهک قارچ خوراکی، Pseudomonas tolaasii ، توسط برخی از ایزوله‌های باکتری‌های همراه قارچ‌های کلاهک‌دار خودرو

Pseudomonas tolaasii causes brown blotch disease in the economically important cultivated mushroom Agaricus bisporus. This bacterium could produce toxin of lipodepsipeptide groups, named tolaasiin, that causes brown blotches on mushroom caps and rotting the beneath. Nowadays, using biological control methods has been increased for plant disease control, due to the problems caused by the increasing application of chemical pesticides and antibiotics in agricultural systems. The objective of the present work is to study tolaasin detoxifying abilities by endofungal bacteria, isolated from wild mushrooms and their potential ability to reduce or eliminate disease symptoms. For tolaasiin extraction, 100 µl of P.tolaasii suspension (with 108 cell/ml density) inoculated in 100 ml of PAF-Broth and PSB media. After the incubation time in optimum circumstance, culture was centrifuged and its supernatant (T-PAF and PSB-Tol) containing tolaasiin, was prepared. Then, 25 bacterial isolates of various species, previously isolated from wild mushrooms from the western parts of IRAN, were selected; and 100 µl of each isolate suspension (with 108 cell/ml density) inoculated in 100ml of PSB and KB media. After the incubation time for each one, T-PAF and PSB-Tol were inoculated to these media. The obtained culture mixtures were centrifuged at 4˚C, and 50 µl of the supernatants were applied onto potato tuber slices, wherein tuber slices normally become blackened due to the toxicity of tolaasin. To determine the correlation between the detoxifying tolassin and disease control ability by endofungal bacterial isolates, detoxifying tolaasiin bacteria were selected and together with P. tolaasii were inoculated on mushroom cap blocks. The results showed that 12 isolates out of 25 endofungal bacteria detoxified tolaasiin as witnessed in the blackened potato tuber slices. Also, four strains out of 12 detoxifying tolasiin isolates, i.e. Pseudomonas taiwanensis, Pseudomonas koreensis, Brochothrix thermosphacta and Bacillus mycoides, and eight unknowing isolates controlled the disease completely. In addition, although Pseudomonas chlororaphis could detoxify tolaasiin but didn’t control the disease. Accordingly, it could be concluded that tolaasiin is a secondary metabolite that is one of the important pathogenisity factors of P. tolaasii. It became clear that these bacteria may have a role in detoxifying tolaasiin, and could have the potential of controlling mushroom cap diseases as a biological controlling agent.