| Crops reduction is mainly due to fungal diseases and currently the chemical control is the main prevention and control measures of plant diseases,and the long-term use of chemicals will not only produce mutations in pathogenic microorganisms,but also cause some pollution to the environment.The use of plant endophytic bacteria to prevent disease,it will not cause the above effects.In this study,taking corn spot,corn withered and corn stalk rot as the target,the endophytic bacteria of Eucommia ulmoides were preliminarily screened,identified and phylogenetic analysis,to clarify the population composition characteristics of Eucommia ulmoides endophytic bacteria and study the colnization characteristics of antagonistic strains in maize plants and their colonization in maize;the effects of biocontrol on the disease resistance of maize were analyzed,to clarify the mechanism of biocontrol colonization in maize and improve the disease resistance.This study can expand the functional diversity and application perspective of biocontrol bacteria,and in the prevention and control of plant diseases is of great significance.Below are key research findings:1.A total of 55 endophytic bacteria were isolated from roots,stems and leaves of healthy Eucommia ulmoides by dilution coating plate method.55 strains of endophytic bacteria were identified by molecular biology experiments,and results belongs to 5 genera:Bacillus sp.,Paenibacillus sp.,Burkholderia sp.,Cupriavidus sp,Lysinibacillus sp.,in which,Bacillus genus was distributed in roots and leaves,39strains,accounting for 70.91%of the total.2.The inhibitory effects of 55 endophytic fungi on Bipolaris maydis,Rhellozoctonia solani and Fusarium moniliforme were determined by plate confinement and mycelial growth rate method.The results showed that the endophytic bacteria DZSY21 had inhibitory effect on maize leaf spot,corn sheath blight and maize stem stalk in vitro,and the inhibitory rates were 61.30%,50%and 79.10%respectively.The results of the subsequent in vivo experiments showed that the control effect of endophytic bacteria DZSY21(1.0×10 ~6 CFU/mL)on maize plants was 62.43%on the sixth day after inoculation to maize plants challenged with corn leaf spot;significantly higher than 50%carbendazim Powder 600 times the control effect of 29.66%.And the introduction of endophytic bacteria DZSY21 will not affect the growth of maize plants.In view of DZSY21 better physical control effect,which can be used as a better development and application of biocontrol bacteria,have further research and development and utilization of the value.3.To study the physiological characteristics of endophytic antagonistic bacteria DZSY21,we found that strain DZSY21 could form thick and biofilm,and had strong swarming motility and chemotaxis to maize root exudates.The colonization dynamics of antagonistic strain DZSY21 in maize plants was detected by transmission electron microscopy and antibiotic labeling,we knew that DZSY21 can be colonized in maize,and the population density increased to 6.35×103 CFU/g per gram of leaf tissue and remained at 2.17 x 103 CFU/g until 30 days to stabilize after 15 days of inoculation with DZSY21.Thence,we believe that DZSY21 forms a harmonious symbiotic relationship with maize.4.To further study the strain DZSY21 to enhance the disease resistance mechanism of maize,MALDI-TOF-MS technology was used to find that the strain DZSY21 could produce three kinds of antibacterial lipopeptides,such as surfactant A,surfactant B and fenaparin,and the expression of defense enzymes such as PPO,POD and PAL in plants were significantly enhanced after DZSY21 introduced into maize plants;Further induction of systemic resistance(ISR)signaling pathway showed that the expression characteristics of the key gene PR-1 and LOX in SA signal transduction pathway and JA signal transduction pathway respectively were up-regulated by DZSY21 after antagonistic endophytic bacteria DZSY21 introduced into maize plants,indicating that DZSY21 introduced into maize plants can activate the expression of defense genes in salicylic acid(SA)and jasmonic acid(JA)signaling pathway in maize to enhance the resistance of maize. |
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