Preliminary Study On The Preventive And Promoting Effects Of Microbial Seed Coating Agents On Maize Diseases And Their Mechanisms

As an annual gramineous crop,maize has become one of the most important food crops and energy crop in the world.Since 2012,it has become the largest crop in China and even the world in terms of yield and planting area.In recent years,areas with severe corn stem rot worldwide have endangered yields by over 40%,and when severe corn leaf spot disease occurs,yields have been reduced by over 50%.Therefore,improving the stress resistance and total yield of corn has become an important research direction for agricultural development in China.Traditional chemical control often brings about the "3R" problem,and microbial seed coating agents are important,effective,convenient,and economical plant protection methods for preventing and controlling pests and diseases in agricultural production practices.The main research content of this article is to screen strains with biocontrol potential using the plate confrontation method,and conduct tests on iron carriers,indoleacetic acid,ACC deaminase,etc.High efficiency biocontrol strains are identified using morphology and molecular biology.The selected strains and chemical additives are configured as microbial seed coating agents for corn disease prevention,growth promotion,and other experiments.The microbial seed coating agents are applied to the field to evaluate their effects on corn growth and development.Using High throughput sequencing technology to analyze the diversity of microorganisms in the rhizosphere soil of maize in the field,based on the impact of disease prevention and yield.The main results of the study are as follows:1.Five bacterial and five fungal strains were screened from 120 strains for testing,which have biocontrol potential.Bacterial M173 has the best antagonistic effect against corn stalk rot pathogen and corn leaf spot pathogen,with antibacterial rates of 69.49% and 76.86%,respectively.Fungal P1 has the best antagonistic effect against corn stalk rot pathogen,with an antibacterial rate of 78.67%;Molecular biology identification was performed on 10 active strains,with M717 and M813 being Bacillus pumilus,M173 being Bacillus velezensis,M834 being Bacillus spizizenii,T1 is Trichoderma harzianum,M620 is Trichoderma gamsii,and M476 is Trichoderma afroharzianum;Bacterial M575 has the strongest iron production ability,with a solubility index of 3.03 and an iron carrier activity unit of 66.67%.Fungal P1 has the highest solubility index of 1.52;M173,M813,and M834 exhibit certain ACC deaminase activity.2.Microbial seed coating agents can prevent and control corn stem rot and improve corn germination rate.The compound type seed coating agent has the highest control effect of 83.91%,with a germination growth rate of 36.38%.The control effect of M173 is 82.24%,with a germination growth rate of 45.46%;In the experiment of controlling maize leaf spot disease,the compound seed coating agent had the highest control effect of51.21%;Microbial seed coating agents can increase the plant height,stem diameter,and dry weight of corn.The growth rates of plant height for T1 and composite seed coating agents are 12.16% and 11.3%,respectively.The growth rate of stem diameter for M1 coated corn is 14.8%,the growth rate of single plant dry weight for composite seed coating agent is 20.78%,and the growth rate of single plant dry weight for M173 coated corn is19.48%;Microorganisms can colonize and form 105-106 cfu/grain on corn seeds.3.In the field investigation of controlling maize leaf spot disease,the relative control effects of the composite seed coating agent,P1,and T1 were better,with 67.43%,65.69%,and 65.11%,respectively;By measuring the yield,it was found that the compound seed coating agent and P1 had the best yield increasing effect,with yields increasing by 25.16%and 21.07%,respectively.T1 and M1 had better yield increasing effects,with yields increasing by 11.46% and 11.19%,and the yield increasing ratio of chemical drugs was 8.02%.4.There was no significant difference between the groups of compound seed coating agent,T1,P1,M1,assistant control,chemical agent and blank control in the number of microbial species in the rhizosphere soil,Shannon index and simpson index.The microbial diversity in the rhizosphere soil of compound seed coating agent was slightly lower than that of the blank control group.Among the bacteria,the relative abundance of Proteobacteria,Chloroflexi and Gemmatimonadetes in the corn rhizosphere soil coated with the compound seed coating agent increased,and the growth rate was 9.76%,18.45% and 11.91%respectively compared with the blank control.Among fungi,the relative abundance of Ascomycota in maize rhizosphere soil coated with compound seed coating agent increased by 12.8% compared with the blank control.The difference species between the compound seed coating agent and the blank control are Sphingobium,Novosphingobiu,Candidatus Nitrospira nitrificans and Nitrospira sp.SG-bin1.