Screening,fermentation And Control Effects Of Antagonistic Bacteria Against Lily Blight

Lily is a perennial bulb herb of the genus Liliaceae with high edible and medicinal value.As the planting area increased year by year,the blight of lily increased year by year,which reduced the quality and yield of lily.Chemical agents are commonly used to control lily blight,but long-term use of chemical pesticides not only enhances the resistance of pathogenic bacteria,but also destroys the ecological balance of the soil and causes environmental pollution.Biological control is an effective method that it is environmentally friendly and is not prone to develop drug resistance.Therefore,the purpose of this study is to isolate and screen the antagonistic bacteria with significant inhibitory effects on lily blight from the soil,and to identify the strains with the strongest antagonistic ability,so as to study the antibacterial spectrum,growth promotion,production and control effects and fermentation conditions of the target strains.The main conclusions are as follows:1.Screening and identification of strains;Taking Lily blight pathogen as target pathogen,37 strains with antagonistic effects were isolated and selected from soil samples.Among them,strain Y25 has the strongest antagonism effects to Lily blight pathogen,with an inhibition zone diameter of 32.75 mm;strain Y25 showed strong inhibition effects on Phycomycetes,Fusarium lini Bolley,Fla Anthrax,Flax wilt,Fusarium wilt of cucumber,Rape sclerotia;strain Y25 has the ability to produce indacetic acid,phosphate and ammonia;Through morphological observation,physiological and biochemical characteristics and 16S rDNA sequence analysis,strain Y25 was identified as Bacillus subtilis.2.The indoor pot experiment showed that,compared with the control group,the incidence rate was 53.5%and the disease index was 37.77 in the absence of Y25;after treatment with the fermentation liquid of Y25 strain with a concentration of 1×108 cfu/mL,the incidence rate was as low as 17.7%,the disease index is 9.44,and the disease prevention effect was as high as 66.79%.3.Field cultivation experiments showed that the control effect of strain Y25 at a concentration of 1×108 cfu/mL against lily blight was only 60.34%;in addition,strain Y25 can also significantly promoted the growth of lily plants,compared with the control group:the average plant increased by 35.23%,the average stem thickness increased by 42.47%,the total plant mass(excluding seed balls)increased by 221.16%,the average seed weight increased by 25.91%.4.Shaking flask fermentation process optimization Through single factor experiment and response surface optimization,the optimum conditions for spore production by shaking flask fermentation of strain Y25 were obtained.The loading volume was 75 mL,pH7.5,corn flour was 16.3 g/L,peptone was 10 g/L,KH2PO4 was 0.8 g/L,inoculation amount was 2%,rotation speed was 240 rpm,temperature was at 40℃ incubation time was 36 h,the measured spore concentration was 3.39 ×1010 cfu·mL-1.After optimization,the spore concentration increased 143 times.