عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Sugar beet is among the most important crops in Iran. One of the main causes of the decline in sugar beet production is root rot, damping off and leaf blight caused by R. solani (Kuhn). Unfortunately, chemical control method against soil-borne fungi especially R. solani in sugar beet is not very effective. In this study the control of R. solani by antagonistic aspects of P. oligandrum using six isolates were studied under various laboratory methods including microscopic investigation of the relation of hyphae between antagonist and pathogen, food competition, the effect of volatile compounds, the effects of extracellular fluid secretion in cultured and heat-stable antifungal metabolites. Microscopic observations showed that P. oligandrum hyphae upon contact with R. solani hyphae wrapped around them, caused protoplast shrinkage which resulted in detachment of the protoplast from the cell walls of R. solani , also oospore formed on the hyphae of R. solani. The results of dual culture tests howed that Torbat-e-jam and Mashhad isolates of P. oligandrum had the most food competition with R solani. In volatile compounds tests using 36 hrs-old colony of the antagonist, the isolate of Torbat-e-jam had maximum inhibitory effect (56.41%) on R. solani in vitro. The extracellular fluids of isolate of Mashhad was %71.31 percent more effective than the control and concentrations of 30%, 40% and 50% extracellular fluid of isolates from Torbat-e-jam had the most growth inhibition on R. solani mycelium in culture medium, However there was no significant difference among the mentioned concentrations. Evaluation of efficiency of P. oligandrum in inhibition of mycelial growth of R. solani in soil showed that the most inhibition of mycelium growth of R. solani (32%) was occurred when soil was solely inoculated with P. oligandrum. The heat-resistant extracellular fluids of isolate of Torbat-e-jam were %71.36 percent more effective than the control in inhibiting the growth of R. solani.