بررسی اثر بازدارندگی پنج جدایه از قارچ Trichoderma روی قارچ Rhizoctonia solani عامل پوسیدگی ریشه کلزا در شرایط آزمایشگاهی

R. solani is a widely distributed fungi around the world, causing some diseases such as root rot, seedling death, canker, degradation of fruit and even foliar blight in various products. Due to the fact that the pathogens of seedling death are soil-born, the use of chemical methods such as coating the seeds with chemical pesticides or spraying of the fields does not lead into satisfactory results. Therefore, in recent years, attention has been paid to the biological controlling, especially the use of antagonist fungi. In this study, the effect of five different isolates of Trichoderma fungi including T. harzianum T13, T. harzianum B22, T. longibrachiatum s3, T. longibrachiatum b4, T. Longibrachiatum m1 on the growth inhibition of R. solani AG2-1 species considering laboratory conditions in a completely randomized design was investigated in 4 replications, and the inhibitory rate of antagonistic isolates in cross-culture methods, the effect of volatile metabolites and the effect of extracellular secretions in concentrations of 0 (control), 10, 20, 30, and 40 were speculated. In cross-culture experiment, all isolates of Trichoderma had a significant effect (at 1% level) on the decrease of the pathogenic fungi growth, and in comparison, T. longibrachiatum s3 isolate had the highest and T. harzianum B22 isolate showed the least inhibitory effect. Through investigating the effect of volatile metabolites, the effect of different treatments on the growth of the pathogen was found to be significant (at 1% level), and in means comparison, T. harzianum T13 isolate had the most inhibitory effect, while the T. harzianum B22 isolate with the least inhibitory effect was observed in the control group. Also, the effect of extracellular antagonist secretions on the growth of the pathogen in different isolates and different concentrations showed a statistically significant difference (at 1% level), so that extracellular secretion of T. harzianum T13 isolate in the concentration of 40% had the most inhibitory effect and was solely observed in the most effective group, and also in this case, T. harzianum B22 secretions in the concentration of 10% had the lowest inhibitory effect compared to the control group. The results of this research indicated that T. longibrachiatum s3 through direct interaction and T. harzianum T13 through the production of the metabolites were the most effective isolates in this study to control the growth of R. solani fungi.