The Nematicidal Activity And Active Components Analysis Of Streptomyces Rochei Strain ZZ-9

In this experiment,the second instar larva of Meloidogyne incognite was used as the target,and Streptomyces rochei strain ZZ-9(Strain retention number:CGMCC No.15245)was used as the experimental strain.The toxicity of live Streptomyces solution and fermentation filtrate of strain ZZ-9 to the second instar larvae of M.incognite was determined.Then the fermentation filtrate was mixed with Avermectin and fosthiazate,in order to achieve synergistic interaction and reduce the use of chemical pesticides,and provide a theoretical basis for field efficacy.The nematicidal active substance in the fermentation broth of strain ZZ-9 was separated and analyzed,and its nematicidal activity was determined.The research results obtained are as follows:1.The nematicidal activity of the live Streptomyces solution and fermentation filtrates of different dilutions of strain ZZ-9 were determined.The results showed that:The stock solution of live Streptomyces solution and fermentation filtrate had the highest toxicity to second instar larvae,and the corrected mortality rate of second instar larvae reached 75.26%and 69.84%,respectively.The fermentation filtrate and the Avermectin solution were mixed in different proportions,and the toxicity to the second instar larvae was stronger than that of using only Avermectin or only the fermentation filtrate,and the higher the proportion of the fermentation filtrate,the better the nematicidal effect.When the fermentation filtrate was mixed with the Avermectin solution(concentration:1.0?g·mL^-1)in a ratio of 3:1,the second instar larvae were treated for 120 h,and the corrected mortality rate was 85.71%,LC₅₀=0.3247?g·mL^-1.When the fermentation filtrate and fosthiazate were mixed in different proportions,the nematicidal effect decreased as the proportion of the fermentation filtrate increased.When the fermentation filtrate was mixed with the fosthiazate solution(concentration:1.0?g·mL^-1)in a ratio of 1:1,the second instar larvae were treated for 120 h,and the corrected mortality rate was 95.76%,LC₅₀=0.1072?g·mL^-1.2.The fermentation broth of strain ZZ-9 was centrifuged,filtered,extracted,and evaporated to obtain a crude extract of nematicidal activity of ZZ-9 strain.When the concentration of the crude extract was 5.0 mg·mL^-11 and the second instar larvae were treated for 24 h,the corrected mortality rate reached 76.67%,LC₅₀=1.2489 mg·mL^-1.The crude extract was treated with thin layer chromatography and silica gel column chromatography to obtain a component ZZ-9-3having nematicidal activity.The infrared light spectrum analysis,nuclear magnetic spectrum analysis and gas chromatography-mass spectrometry were used to analyze ZZ-9-3,and the main substances contained in ZZ-9-3 were identified as tributyl phosphate,dibutyl phthalate and cyclo(Leu-Leu).3.The nematicidal activity assays for tributyl phosphate,dibutyl phthalate and cyclo(Leu-Leu)showed that they all had certain nematicidal activity.Among them,tributyl phosphate had the best effect.When the concentration of tributyl phosphate was 5.0 mg·mL^-1and the second instar larvae were treated for 24 h,the corrected mortality rate reached 81.67%.The effect of dibutyl phthalate was second,and the corrected mortality rate was 73.33%.Cyclo(Leu-Leu)showed low toxicity to the second instar larvae,and the corrected mortality rate was 38.33%.The tributyl phosphate and dibutyl phthalate were mixed in a ratio of 1:1 to determine the nematicidal activity.The results showed that the nematicidal effect after compounding was slightly improved compared with the single used,but the effect was not obvious,and the corrected mortality rate was 85.00%.