Screening,identification And Fermentation Optimization Of Biocontrol Bacteria Against Potato Scab In Heilongjiang Province

Potato is considered to be the fourth largest food crop in the world,which is rich in nutrients and energy,and low in calories.It meets the requirements of healthy diet and is loved by people all over the world.In 2015,China also included potatoes in the main food list.However,potato common scab(PCS)caused the decline of potato quality,which caused the rejection of consumers and manufacturers,resulting in increasingly serious economic losses.And there is still a lack of effective measures to solve potato scab.In recent years,due to the use of biological agents on the natural environment has a very small adverse impact and has a strong targeted pathogen,and has been concerned.In this experiment,Stretpomyces scabies,one of the main pathogenic bacteria in Heilongjiang Province,was taken as the target pathogen,and Bacillus spp.was isolated from the soil of the affected area in Heilongjiang Province.Thirty antagonistic strains were screened preliminarily from 6 samples by plate confrontation method,and then screened again by Oxford cup method.The AMCC102004 strain with better antagonistic effect was selected from the fermentation supernatant of antagonistic bacteria for further biocontrol test and identification.The optimal fermentation conditions of the strain were explored by fermentation optimization.In pot experiment,the biocontrol efficiency of strain AMCC102004 reached 51.52%.The results of pot experiment showed that strain AMCC102004 could reduce the incidence,morbidity coefficient and disease index of potato,and had a good effect on the control of potato scab caused by Stretpomyces scabies.Multiple classification methods were used to systematically identify the screened strains,including morphological identification,Biolog systematic analysis and 16S r DNA molecular identification,strain AMCC102004 is preliminarily identified as Bacillus altitudinis.Optimization of fermentation of Bacillus altitudinis AMCC102004 strain.The single factor experiment show that wheat bran is the best carbon source,soybean meal is the best nitrogen source,and sodium chloride is the best inorganic salt.Then,the optimal level of each factor was tested with the three components.The results showed that the optimal levels of each factor were as follows:the concentration of wheat bran is 2%,the concentration of soybean meal is 2%,the concentration of sodium chloride is 0.3%,the initial p H is 7.5,the inoculation amount is 2%,the culture temperature is 32℃,and the fermentation time is 24 h.Plackett Burman test showed that nitrogen source,initial p H and fermentation time are the main influencing factors.According to the results of response surface optimization,the maximum biomass of 3.26×10~9CFU/m L is predicted when the content of soybean meal is2.076%,initial p H is 7.422 and fermentation time is 24.105 h.