| Since the year of 2015 our country put forward the strategy of potato as staple food,the planting area and yield of potato in China are increasing year by year.However,potato late blight caused by Phytophthora infestans is the most influenced and destructive plant disease,therefore,potato late blight has been considered as the first plant disease in the world.At present,the main measures for Preventing and controlling of potato late blight contain agricultural prevention and control,selection of disease resistant potato varieties,chemical pesticide and biological control.To begin with,there is no denying the fact that agricultural prevention and control is time-consuming and laborious and is difficult to eradicate the infection of potato late blight.Besides,because of rapid mutation and increasingly complicated mating type of P.infestans,the breeding speed of disease resistant varieties is far less than the rate of resistance decline of potato caused by pathogens.In addition,the continuous selection of chemical pesticides has contributed to the more frequent variation of P.infestans,plus it is high time for us to pay attation to the pollution of human living environment caused by using a large amount of chemical pesticide.As a consequence,it is urge for us to explore new,efficient,safe and environmentally friendly biological control methods.In recent years,the biological control measures based on microorganism living body and its metabolites are attracting much attention due to theirs effective work,no pollution to the environment and without causing resistance to pathogens.Our group recently has screened out 6 strains inclued WL1,M15,WL2,and etal.,and those6 strains have significant inhibitory effect on P.infestans and have obvious effect in vitro tissue test.Because those strains were screened with different person during different period,so it is worth further comparison and discussion about which strain of six has the great biocontrol potential.Meanwhile,the classification status as well as the stability of inhibitory activity and the types of antagonistic substances of having the most biocontrol potential strain needs to be further clarified.The main contents of this experiment are as follows:(1)Further comparison of 6 strains with certain inhibitory effect on inhibiting the growth of P.infestans mycelia growth,spores germination and the ability in controlling potato late blight in vitro in order to obtain the strain which have the most potential.(2)Identify the classification status and inhibition stability of WL2 which is the most potential strain.(3)Determination the ability of Bacillus subtilis WL2in producing lipopeptides as well as the types of lipopeptides.(4)Identify the effect of lipopeptides produced by WL2 strain on the prevention and treatment of potato late blight and the growth promoting effect on potato plants.The main results are as follows in this experiment:1.By comparing biocontrol effect of 6 strains,having the most biocontrol potential strain of WL2 was determined.The inhibitory zones of WL2 living bacteria,bacterial liquid and fermented liquid to P.infestans growth were above 26mm,and the rate of mycelial malformation caused by WL2 was up to 38.7%.Besides,the percentage of zoospore release,sporangium direct germination and zoospore germination treated with the minimum bacterial liquids concentration(1×10~4 cfu/mL)of WL2 were 33.8%?28.3%and 35.4%,respectively and all lower than that of the other strains.In addition,WL2 bacterial liquid acquired the best disease prevention on in vitro leaves and tubers in comparison with the other 5 strains,and the relative protection ratio was up to 81.2%and 80.5%respectively.2.WL2 strain was identified as B.subtilis by estimating culture characterization,biochemical and 16S rDNA gene sequencing.3.B.subtilis WL2 has stable inhibitory effect,inhibitory rates of WL2 strain fermentation broth after treatment with 121?was more than 50%,inhibitory rates over 70%after the treatment of pH 2~12,and fermentation broth still had strong inhibitory rates(over77%)after exposure for 12 hours under UV lamp.Furthermore,fermentation broth of WL2strain could be stored for at least 1 year under the condition of 4?with its biocontrol activity.4.B.subtilis WL2 had the ability of producing lipopeptide.This strain could produce obvious haemophilus circle as well as oil phagocytosis circle,and fermentation liquid of WL2had the effect of oil displacement,and the diameter of oil displacement was up to 4.9 cm.Besides,the emulsifying property percentage of fermentation broth was as high as 85.5%.5.B.subtilis WL2 could produce lipopeptides of IturinA and Surfactin.6.Lipopeptides had the inhibitory effect on P.infestans,and the inhibitory effect depended on its concentration.Diameter of inhibition zone was 0.59 cm after the treatment of lipopeptide at the concentration of 25?g/m L,and sporangium direct germination rate was only 9.7%when the lipopeptide concentration was at 3?g/mL,besides,zoospore release rate was only 7.6%with the lipopeptide concentration at 4?g/mL,in addition,the time of lipopeptide inhibited both zoospore release and sporangium direct germination were only1.5h.7.Lipopeptides had a great biocontrol effect on potato late blight and was suitable to be used for prevention.8.Lipopeptides at the concentration of 20?g/m L acquired a great prevention effect on in vitro tubers and leaves,and the disease index were 20.6 and 17.5 respectively.Moreover,lipopeptides could significantly promote defense-related enzymes(PPO,POD,PAL)activity.Besides,lipopeptides played a certain role in promoting growth of potato plants,and could promote chlorophyll content increase about 15%,diameter of root increase 11.9%,and root dry weight increase 11.2%.In addition,lipopeptides could also promote main stem diameter of potato plants increase 9.8%,main stem dry weight increase 16.7%,and offspring production increase about 14.8%. 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