The Induction Of Antagonistic Effect Of Phytophthora Infestans To Streptomyces Microflavus Sy11 Strain

Patato late blight is caused by Phytophthora infestans,it is a oomycets diease which damages potato production.Once Potato late blight outbreak,it will cause a significant decline in the quality and yield of potatoes,even extremely.As the word's fourth largest food crop,the first question of ensuring the quality and yield of potatoes is how to effectively control potato late blight.At present,it is widely noted that use of antagonistic microorganisms for biological control of potato late blight has the advantages of green,lasting effect,and a great potential.Our lab fot a strain of actinomycetes,named Sy11,which significantly could inhibit the mycelial growth of P.infestans in previous experiments,the inhibition rate reaches 86.47%,but both fermentation broth(FB)and concentrated FB without Sy11 living had no suppression on P.infestans.The Sy11 strain was identified as Streptomyces microflavus.Sy11 strain had response to P.infestans,and could produce and secrete some substances inhibiting P.infestans.In this study,we first verified the correctness of this conjecture and established the co-culture model of P.infestans and Sy11 in based on solid culture medium,analyzed the size of the inductors in liquid mixed fermentation,and discussed the inhibitory effects of chemical and biological agents on inducible factors,provided the reference for the future application of Sy11 in agriculture.The main results obtained in this study are as follows:1.It was verified that the P.infestans induced Sy11 produced metabolites inhibiting P.infestans.The study established a co-culture model of P.infestans and Sy11: P.infestans and Sy11 mushroom cakes(7mm)cultured on rye medium 10 d under 20?,the distance between two cakes was 72 mm,the antimicrobial activity of the metabolites produced by Sy11 was the highest.2.P.infestans secreted the substance which induced Sy11 during co-culture,and the condition of the highest activity of inducing substance is 20?co-culture for 5d.3.When inoculated with P.infestans and Sy11 in liquid media,first inoculatedP.infestans cake(7mm*3)for 5d,then inoculated Sy11 cake(7mm*3),cultured for 10 d,and then removed the bacteria from the FB.The supernatant of FB had inhibition activity.The P.infestans or Sy11 was placed in the dialysis bag(10kD)for co-culture respectively,and the supernatant of the FB without bacteriostasis showed no inhibition activity,indicating that the molecular weight of the signal molecule was greater than 10 kD.4.The inhibitors of signal molecules between P.infestans and Sy11 were discussed.The activities of signal molecules were inhibited by metalaxyl·mancozeb,sodium benzoate and sodium acetate at 50?g/m L and 5?g/mL,and the crude extract of potato flavone at 100?g/mL can promote the induction.5.The extraction conditions of flavone from potato were optimized,time,temperature,solid-liquid ratio and ethanol volume fraction of 4 single factors were tested.According to the test results,selected temperature,solid-liquid ratio and ethanol volume fraction el 3factors for response surface analysis,finally got the optimal extraction conditions of flavone from potato: the ratio of material to liquid at 1:36,79?,ethanol volume fraction 55%,the extraction rate of flavonoids obtained was 1.304%.