| Corn is one of the main grains in China.Because of its rich crude fiber,vitamins,trace elements and a large number of proteins,it has a high economic development prospect and research value.One of the important factors affecting corn yield is the infection of soil borne diseases.Corn stalk rot,also known as stem-based rot or bacterial wilt,is a common soil borne disease in the world's corn production areas and one of the major diseases in China's corn production areas.In agriculture,the control of soil borne diseases is usually carried out by applying chemical pesticides.However,the long-term use of chemical pesticides has led to a wide range of environmental pollution,so the biological control methods to reduce or replace the use of chemical pesticides have received widespread attention.Seed coating technology is one of the important means to control diseases and insect pests.At present,most of the corn seed coating agents used in the market are pesticide seed coating agents.There are many problems in the market,such as the aging of agents,the instability of properties,the high rate of coating off,and the application of microorganisms in corn seed coating agents is relatively small.Therefore,it is very important to study the biological seed coating agent for the control of corn diseases.In this experiment,strains with both biocontrol and growth promoting effects were selected from the microbial strain Resource Bank of the laboratory.They were compounded with other additives to form an environmental friendly biological seed coating agent,which was applied in the pot planting of corn to explore the impact on the growth of corn seedling.The main research results are as follows:1.In this experiment,24 different strains were selected,and 5 strains and 1 strain of Trichoderma were screened to inhibit the pathogen of corn stalk rot by plate confrontation test.Through the determination of physiological indexes,6 strains of bacillus which have the potential to promote the growth of corn seeds were obtained.They have the ability to produce IAA and iron carriers.Based on the two functions ofbacteriostasis and growth promotion,TXM-1(Bacillus velezensis)and TXM-2(Bacillus amyloliquefaciens)were selected as the active components of biological seed coating agents.On the basis of the above experiments,in the study,TXMT-3(Trichoderma reesei)with bacteriostatic effect and TXM-7(Bacillus cereus)with growth promoting ability will be combined(the strains can coexist),and they will work together.Through the germination pot experiment of corn seeds,the best ratio of the two was selected as the active component of biological seed coating agent.2.The physical and chemical properties of the film-forming agent were studied from three aspects: film-forming time,coating uniformity and coating off rate.In this experiment,four ratios of 90:10,60:40,30:70 and 10:90 were selected for the next study.Through the germination test and strain activity test of corn seeds with different proportion of film-forming agent,the effect of film-forming agent on the growth of corn seedling and the active components of seed coating agent was studied.The results showed that the film-forming agent with SA: PVA = 1:9 not only promoted the growth of corn,but also slowed down the activity of strain.In addition,this experiment also studied the dynamic change of the mixture of bacterial agent and film-forming agent.With the increase of time,the composition ratio of five kinds of coating agents and microbial agents was determined by measuring the activity of strains,and the storage time of biological seed coating agents at room temperature was roughly estimated to be at least two months.3.Four kinds of biological seed coating agents(BSCA-1,BSCA-2,BSCA-3,BSCA-4 and BSCA-5)were obtained in the experiment,which have the functions of antagonizing pathogens and promoting the growth of maize seedling.The formulas are TXM-1,TXM-2,TXMT-3,TXMT-3 and TXM-7,respectively(1:4 and 3:2)were active components,sodium alginate and polyvinyl alcohol were used as film forming agents,bentonite and sodium benzoate were used as auxiliary agents.Five kinds of biological seed coating agents were used in pot experiments,and it was found that they can promote the seedling growth of maize.After the treatment of BSCA-1,BSCA-2,BSCA-3 and BSCA-4,the POD enzyme activity of the early growth of seeds increased;after the treatment of BSCA-1,BSCA-2,BSCA-3 and BSCA-5,the chlorophyll content of corn seedling increased significantly;after the treatment of five kinds of coating agents,the malondialdehyde content decreased significantly.BSCA-1 has the best effect on the growth of maize.The results showed that the biological seed coating agent basedon Bacillus and Trichoderma could not only antagonize the pathogen of corn stalk rot,but also promote the growth of corn seedling,which revealed its potential to replace the chemical seed coating agent in corn planting.4.BSCA-1 was used in corn planting,and the results showed its excellent application effect.In this paper,TXM-2 was applied to spinach and lettuce to verify its growth promoting and bacteriostatic effects.The results showed that TXM-2 had the function of inhibiting the disease infection on lettuce,and it was also tested with other pathogens stored in the laboratory.The broad-spectrum bacteriostasis of TXM-2 was found,and the potential of TXM-2 as biological control agent in crop planting was revealed.The results showed that the relative abundances of Acidobacteria and Actinobacteria were higher than those of CK,and the number of OTUs was 4.96%higher than that of CK,which indicated that TXM-2 may have the same ability to recruit other microorganisms Ability to promote crop growth. |
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