Screening And Identification Of Staphylococcus Nematicides AMCC1020 And Study Of Its Active Substances Against Nematode

Root knot nematode（Meloidogyne spp.）is one of the most economically destructive plant parasitic nematodes in horticulture and field crops.The annual loss of Meloidogyne spp.is about 100 billion US dollars,which seriously restricts the development of agriculture in the world.In modern agriculture,chemical control is the main control method of root knot nematode disease,but due to various problems caused by chemical control,people gradually shift their vision to biological control.Based on the test results of nematicidal activity of fermentation supernatant,the strain with the best biocontrol effect was selected,and its classification and identification,the basic properties of its active substances were studied,And the extraction,identification and analysis of volatile active components.According to the analysis results,the standard compounds were purchased to verify the insecticidal activity.The main results are as follows:（1）Screening of biocontrol strains against root knot nematode.Through the contact system of Meloidogyne incognita,85 strains of bacteria were fermented in shake flask,and the insecticidal activity test was carried out with the fermentation supernatant of 48 h.The corrected mortality of 7 strains was more than 50%,and 3 strains were more than 80%,of which 1 strain was 91.75%,and the number was AMCC1020.（2）Identification of strains.AMCC1020 was identified as Staphylococcus squirrel by Morphological identification,Biolog physiological and biochemical identification and 16S r DNA molecular identification.（3）Basic properties of active substances.The results of fermentation time test showed that the insecticidal activity of AMCC1020 reached the maximum when the fermentation time was48 h in BPY liquid medium.The effects of different temperature,p H value and storage time on the insecticidal active substances were verified,The results showed that the nematicidal active substance produced by this strain had good acid resistance and poor alkali resistance,and had good temperature stability and storage stability.It was tested after subculture the insecticidal activity showed that the strain had good stability of passage;the solvent extraction method showed that the active substances could not be effectively extracted by four organic solvents,namely n-butanol,ethyl acetate,chloroform and cyclohexane.（4）Extraction,analysis and identification of volatile active substances.Firstly,the insecticidal active substance produced by AMCC1020 was identified as volatile substance by rotary evaporation and redissolution.Then,the volatile active substance was extracted by solid phase microextraction（SPME）technology,and the active substance was analyzed and identified by GC/MS technology.Finally,10 kinds of volatile active substances were identified,which were acids,alcohols,esters,aldehydes and alkanes.（5）Insecticidal effect of standard compound against nematodes.According to the results of analysis and identification,the standard volatile active substances were purchased to test the insecticidal activity of the second instar larvae of Meloidogyne incognita,and the two substances were found to have high insecticidal activity.The LC100 of the two standards to the second instar larvae of Meloidogyne incognita at 12 h was determined.The LC100 of acetic acid at 12 h was 0.1μL·m L^-1,and that of phenylethanol at 12 h was 0.8μL·m L^-1.In conclusion,Staphylococcus sciuri AMCC1020 obtained by screening and identification is a good insecticidal strain.The isolation,purification and research of its nematicidal volatile active substances can provide a reference for the development of new nematicides.