Abstract:Studies were conducted to assess the antagonistic effect of biocontrol fungus,Paecilomyces lilacinus (Thom.) Samson and its mechanism against Fusarium oxysporum Schl.The results showed that the secondary metabolite produced by P.lilacinus obviously suppressed the colony growth,sporulation and germination of F.oxysporum.The antagonistic mechanism against F.oxysporum were mainly related to remarkable nutrient competition and β-glucosidase activity that caused cell wall degradation as well as antibiotic production (such as toxic protein and amylose).The antibiotic substance existed in the hyphae,but it could be released from the hyphae significantly in the later stage of ferment culture.The inhibition rates of extracellular substance and intracellular-1 substance to sporeulation of F.oxysporum were above 90%.Meanwhile,the inhibition rates of extractions of crude protein and crude amylose were about 73%, but that of the substance extracted by acetone solvent extraction was only 25.42%.The secondary metabolite mainly being water-solubility and the antibiotic substance was unable to bear high temperature.When treated by 100 ℃ or 80 ℃ for 30 min,the substance had nearly no inhibition activities.