The Creation And Application Effect Of The Compound Microbial Agent CAP Against Corn Stalk Rot

Corn is the main food crop in our country with low cost and unique quality,it occupies an important position in economic development and agricultural production.However,in corn production,corn stalk rot is one of the main fungal diseases,which has a serious impact on the yield and quality of corn.At present,the control of corn stalk rot is mainly through chemical agents,which not only pollutes the environment,but also increases the resistance of pathogens and makes the prevention and control more difficult.Therefore,biological control has become another option for the prevention and control of corn diseases.Plant endophytes exist in healthy plant tissues and play an important role in plant growth,development and disease resistance.Studies have shown that compared with a single species of biocontrol bacteria,the diversity of microbial communities exhibits stronger protective effects and has a broad application prospects.In this study,the composition of the dominant endophytic bacteria in the corn stalk was analyzed and the cultivation conditions were optimized to obtain endophytic culture groups that antagonized Fusarium graminearum.The sensitivity of the fungicide was determined to clarify the feasibility of compounding.Further study explored its species composition and built an antagonistic,nutritious multifunctional compound bacteria agent to provide a new strategy for the green prevention and control of corn stalk rot.The results were as follows:1.The dominant endophytes of corn stalk are mainly composed of Pseudomonas,Microbacterium,Rhizobium and Bacillus,of which Bacillus only accounts for 6.25%.2.By optimizing the culture conditions,four groups(A,B,C,D)derived from corn stalks were obtained with good inhibitory activity against F.graminearum endophyte culture groups and the radius of the inhibition zone was 1.45,1.41,1.38,1.17 cm respectively.The antagonistic effects on F.graminearum were analyzed using different concentrations of endophytic bacteria culture groups.The results showed that the A and B culture groups showed strong inhibitory activity.When the concentration was 107 cfu/mL,the inhibition rate reached more than 90%.The sensitivity test of fungicides showed that when the concentration of pyraclostrobin was 50 mg/L,the A culture group was less sensitive to it.After the A culture group was compounded with 50 mg/L pyraclostrobin,the inhibitory effect to F.graminearum reached more than 98%.Field test results showed that the compound culture group A had the same effect as the normal dose of fungicides,which reduced the use of chemical fungicides while preventing diseases.3.The culture group A was isolated,cultured,and analyzed by 16S rDNA gene sequencing.The results showed that the culture group A was composed of Bacillus,Pseudomonas,Stenotrophomonas,Acinetobacter,Ochrobactrum,Staphylococcus,Pantoea,among them,Bacillus is the main genus,the proportion is as high as 74.5%.4.The test of the antagonistic activity of the strains in culture group A against F.graminearum showed that:B.amyloliquefaciens,B.velezensis,B.subtilis,B.tequilensis,B.vallismortis,B.cereus,P.aeruginosa have inhibitory effects on F.graminearum,among which P.aeruginosa not only has an inhibitory effect on F.graminearum but also has a certain antagonistic activity against Bacillus.It also has a certain inhibitory effect on other Gram-positive bacteria,so it is not suitable to be used in combination strains.5.The screening results of vegetative endophytes showed that Acinetobacter baumannii,Acinetobacter soli and Pantoea ananatis had better phosphate solubilizing effect on inorganic phosphorus and organic phosphorus;Rhizobium pusense,Pseudomonas fluorescens,and Ochrobactrum anthropi had better effects in dissolving potassium and nitrogen.Among them,R.Pusa was more significant.6.The screening results of the compound bacterial agent CAP showed that:Bacillus cereus,Pantoea ananatis,and Rhizobium pusense have no mutual antagonism.These three bacteria are relatively insensitive to 50 mg/L pyraclostrobin and can be combined and compounded.7.The growth-promoting and antagonistic effect test of the compound bacterial agent CAP showed that:compared with CK and single endophytic bacteria,the compound bacterial agent CAP had a significant promoting effect on the plant height,root length and chlorophyll content of corn.After compounding pyraclostrobin,the inhibition rate against F.graminearum is as high as 97.61%.The field test results showed that compared with a single biocontrol strain,the corn yield and biological control effect of CAP+50 mg/L pyraclostrobin treatment have been improved.