بررسي امكان استفاده از باكتري هاي آنتاگونيست براي كنترل بيولوژيك بيماري مرگ گياهچه پنبه در گلخانه

Investigation on the possibility of using bacterial antagonists for biological control of cotton seedling damping-off in green house

Rhizoctonia solani-induced cotton seedling damping off is one of the most important diseases of cotton in Iran. Since the causal agent is a soil born fungus, chemical control is not always effective. In addition , widespread use of chemicals has resulted in pollution of the environment and appearance of resistant races of the pathogen. The need for the search of alternative methods to control this disease is therefore clearly obvious. Biological control could be a promising alternative method. In this study the possibility of biological control of the disease using bacterial antagonists was investigated. Fifty bacterial isolates, isolated from cotton and sugar beet field soil were first screened against R. solani in the laboratory using dual culture method. Seventeen isolates which showed more effectiveness were selected for further evaluation in the green house. In green house experiments the above-mentioned isolates were tested against pre- and post emergence damping off disease using seed coating and soil drench methods. Analysis of the results showed that 7 out of l7 isolates reduced cotton seedling damping-off significantly (compared to the control). Of the above isolates 4 belonged to Bacillus spp.and the remaining 3 isolates were identified as Pseudomonasfluorescense based on bacteriological identification tests.