Screening And Identification And Preliminary Mechanism Of Biocontrol Bacterial Inducing Maize Resistance To Northern Leaf Blight Of Corn

Northern Leaf Blight of Corn(NLBC)is one of the important diseases in corn production all over the world.NLBC can cause large areas of maize leaves to die and loss maize yield.Under natural conditions,the disease is going to be serious in the middle and late stages of the corn.It is difficult to spray chemical pesticides during these stages,which seriously pollute the environment.In recent years,develop the biological control methods with high control effective,non-toxicity,and pollution-free is a new method to control the NLBC.In this paper,a method was used that coating maize seeds with bacterial fermentation broth.By screening in field and indoor experiments,get some bacterial strains that could induce maize against NLBC.Then,the effective bacteria strains were systematically studied according to classification.And at the same time,preliminary studied on the mechanism of bacterial strain Sneb85 inducing resistance to NLBC at molecular level.The main results were as follows:1.Screening biocontrol bacterial strains that induced maize against NLBC.The fermentation broth of 1800 bacteria strains stored in our laboratory was used to coat maize seeds.The field experiments were conducted in separate years(2018 and 2019)and some indoor experiments were screened and the five bacterial strains were found including Sneb85,Sneb530,Sneb909,Sneb1168 and Sneb1513 that could highly effectively control against the NLBC.Highly effective bacterial strains could promote maize seed germination and seedling growth,also could increase maize yield production in varying degrees.2.Identification of biocontrol bacteria inducing maize against NLBC.Identified by the methods of classical morphological,physiology and biochemical characteristics,molecular biology.The results were analyzed the classification status of all effective bacteria strains.The results showed that Sneb85 was identified the Bacillus megaterium,Sneb530 was Acinetobacter calcoaceticus,Sneb909 was Enterobacter ludwigii,Sneb1168 was Bacillus cereus,Sneb1513 was Pseudomonas azotoformans.3.Research of related defense genes expression in leaves of maize resistant to NLBC induced by Sneb85 treated with seeds.Measure related defense genes with salicylic acid(SA),jasmonic acid(JA)and ethylene(ET)by the method for quantitative real-time PCR.In the process of maize resistant to NLBC induced by Sneb85,LOX1,LOX3 and AOS genes were as representative genes regulating JA signal.At 12 hpi,three genes expression up-regulated.ERF,ACS65 and ACO31 genes were as representative genes regulating ET signal.At 24 hpi,ACO31 gene expression up-regulated.It showed that JA /ET signaling pathway was involved in the early and middle stages of maize against NLBC.PR1,PR5 and OPR2 genes as representative genes regulating SA signal.At 24 hpi,PR5 and OPR2 genes expression significantly upregulated.At 48 hpi,PR1 gene expression also up-regulated.It showed that the SA signaling pathway played a role in the middle and late stages of maize against NLBC.The results showed that related genes of SA,JA/ET signaling played an important role in the process of maize resistant to NLBC induced by Sneb85.It might be that the JA/ET signaling pathway was activated first in the early process of maize against Exserohilum turcicum.With the continuous infection of pathogenic fungus,it might be that SA signaling pathway was activated in the middle process of maize against E.turcicum for improving maize resistance.