Study On Biological Characteristics Of Paecilomyces Lilacinus Strain E7 And Its Efficaey On Plant Root-knot Nematode

Plant parasitic nematodes are one of the important limiting factors in crop production throughout the world. Using chemical agents and nematicides cause many negative effects, while biocontrol can overcome these disadvantages. Paecilomyces lilacinus is one of nematophagous fungi which has been developed into a variety of commercial formulations worldwide over the past decade. In China, intensive research on various aspects of the fungus has undergone for several decades but no formulation has been commercially registered at present. On a basis of previous work on an aphid-derived isolate Str.E7 of Paecilomyces lilacinus in our laboratory, the present study has accomplished the following results.Fermentation biology characteristics of Paecilomyces lilacinus E7 tests showed that temperature is key factor to culturing, it exhibited normal growth in 10℃-37℃. The optimum growth and sporulation occurred at 28℃. Generally speaking, the best ratio of C/N was 8:1 in liquid fermentation, because it is good for biomass developing and sporulation. The effect of different substrate concentration on growth of Paecilomyces lilacinus E7 was studied. Result showed that: lower substrate concentrate was suitable to sporulation increasing quickly, but the mycelia biomass need abstractly high concentrate. So the middle substrate concentration setting(C=0.7mol/L) benefit for biomass. Sugar was better for sporulation than glucose, while organic N was better for sporulation than inorganic N. Cultured with the surge and peptone, the dry weight of biomass and sporulation could reach the max.Single-factor and orthonal tests showed that 3% Soy flour, 2% chitin,0.001% MnSO4 and seeding volume 5% are the best medium for Paecilomyces lilacinus E7 to product proteases,chitinases and sporulation. The proteases peak generally appears in fifth days, wants late compared to chitinases peak two days. In 50L fermentor, the DO decreased generally after 12 hous of fermentation. So the DO should keep above 40%; the best fermenting process only spent 42 hours and the yield of spores could reach a high level of 3×10~9 spores/mL.Study on production of Paecilomyces lilacinus using cassavas process wastewater as raw material, the result showed that the number of spores in cassavas process wastewater with 0.4% carbamide and 0.02%MgSO4 could reach 4.96×10~8个/mL in 4 days.The results of control experiment showed that inoculating Paecilomyces lilacinus E7 was an available method to reduce the nematode damage. The rate of hatching was reduced to about 40% ; the control effect was reached to about 70%,50% and 70% in the pots,plots and fields. So the Paecilomyces lilacinus E7, as nematophagous biological control method, is worthy of generalization.