| Maize stalk rot is one of the most important soil-borne diseases in maize production areas,and the main pathogens causing the disease include Fusarium and Pythium species.The disease harms the base of the maize stalk,causing yield loss and food security,and the toxins secreted by some species of stem rot protoplasm fungi can also harm human and animal health.Therefore,it is very important to prevent and control maize stem base rot.In this thesis,we obtained a strain of maize inter-rhizobacteria TG1 that could inhibit both Fusarium graminearum and Pythium aphanidermatum by dilution isolation and screening of healthy plant inter-rhizobacteria,and initially explored the effect of TG1 on the control of maize stalk rot.In addition,resistance to stalk rot was identified for regional,introgression and consortia maize varieties in Anhui Province.The main findings were as follows:1.170 strains of bacteria were isolated from the roots of healthy plants by dilution isolation method.One strain of TG1 was obtained by the plate standoff method,which showed good antagonistic effect against the stalk rot pathogen of maize.Combining morphological characteristics,physiological and biochemical characteristics and 16S r DNA sequence analysis,TG1 was identified as Burkholderia spp.2.The inhibitory effects of TG1 bacterial suspension,sterile metabolic solution and volatile substances on maize stalk rot pathogens were initially investigated.The results showed that the inhibition rates of TG1 suspension,sterile metabolic solution and volatile substances reached 80.43%,42.37%and 31.61%,respectively,on the growth of F.graminearum mycelium,and 54.37%,41.27%and 15.87%,respectively,on the growth of P.aphanidermatum mycelium.TG1 will make F.graminearum mycelium thinner and more branching;make P.aphanidermatum mycelium crumpled and apical expansion.TG1sterile metabolite solution inhibited conidia formation and germination of F.graminearum.When the sterile metabolite was mixed with CMC spore-producing medium at the ratios of1:1,2:1 and 3:1,the inhibition rates of conidia formation were 34.47%,72.41%and75.86%;respectively;after mixing the sterile metabolite with conidia suspension at the ratios of 1:1,2:1 and 3:1,the germination of conidia was observed,and it was found that after 8 h of incubation,the germination rates of conidia were 9.76%,1.63%and 3.75%,respectively,which were significantly lower than the control spore germination rate of39.32%.3.The cultivation medium and cultivation conditions of TG1 were optimized.The effects of incubation conditions such as temperature,time and p H on the inhibition activity of TG1 metabolite were investigated.The results showed that the metabolic solution had the highest inhibitory activity when TG1 was incubated for 4 d,with 50.33%and 31.77%inhibition of mycelial growth of F.graminearum and P.aphanidermatum,respectively;The metabolic solution showed the highest inhibition activity when TG1 was incubated at28℃,with 24.75%and 39.13%inhibition of mycelial growth of F.graminearum and P.aphanidermatum,respectively;The highest inhibition activity of the metabolic solution was observed when TG1 was incubated at p H 7.5,with 27.94%and 27.10%inhibition of mycelial growth of F.graminearum and P.aphanidermatum,respectively;When TG1medium was LB,the metabolic solution showed the highest inhibition activity,with26.52%and 36.85%inhibition of mycelial growth of F.graminearum and P.aphanidermatum,respectively.The effect of TG1 bacterial concentration on the antibacterial activity of its metabolite was studied,and It was found that the concentration of bacteria was within the range measured by the test,the concentration of TG1 was the highest,and the inhibitory activity of metabolic fluid was the highest.The effect of different carbon,nitrogen and trace element addition substitution on the concentration of TG1 bacteria was investigated by single-factor test,and it was found that the best carbon source for culturing TG1 was galactose,the best nitrogen source was yeast powder and peptone,and the best trace element was threonine.4.The thermal stability and UV stability of TG1 aseptic metabolic solution were studied.The results showed that the inhibitory rate of TG1 metabolic solution on the growth of F.graminearum at 40℃was less significant than that before high temperature treatment,and the inhibitory activity was still 35.71%;but,the inhibitory rate of TG1 metabolic solution on the mycelium growth of P.aphanidermatum at 40℃was only 22.75%,and the inhibitory activity was significantly different from that of the control group.TG1 metabolic fluid was irradiated with ultraviolet light for 10 min to 120 min.The results showed that the inhibition rate of F.graminearum mycelium growth was 36.77%after 10min treatment,which was little different from the control group,but the inhibition rate decreased significantly after 10min treatment.And the inhibition rate of P.aphanidermatum mycelium growth was 16.67%and 2.61%respectively,which was significantly lower than that of the control group.The results indicated that TG1metabolic solution treated at 40℃and short time ultraviolet light had little difference in antibacterial activity against F.graminearum,but,the antibacterial activity of TG1 aseptic metabolic solution decreased with the increase of temperature and UV irradiation time.It was found that TG1 was a biocontrol bacterium with wide bacteriostatic spectrum.5.The ability of TG1 to produce hydrolytic enzymes and the inhibitory effect of TG1 crude protein on the growth of mycelium of maize stalk rot pathogen was investigated.The results revealed that TG1 can produce protease but has a weak capacity to produce cellulase.The crude protein of TG1 was found to inhibit the P.aphanidermatum mycelial growth and production of F.graminearum pigments.Among the crude proteins extracted at different saturation levels of ammonium sulfate,the crude protein extracted at 90%saturation level had the highest inhibitory activity,and the inhibition rate of mycelial growth of P.aphanidermatum reached 33.80%.6.A preliminary study was conducted on the field control effect of TG1 on maize stalk rot,and it was found that the control effect of TG1 on maize stalk rot was directly proportional to the concentration of TG1 cells.Among the two inoculation methods of drilling and root cutting,the TG1 bacterial concentration with the best control effect in the field is 4.92×10~8cfu/m L,with a control effect of 67.97%and 73.76%on maize stalk rot,respectively,proving that TG1 is a biocontrol bacterium with good control effect on maize stem rot in the field.7.Stalk rot resistance was identified in Anhui Province for regional trials varieties,introductions varieties and consortia of corn varieties,it was found that no susceptible or highly susceptible varieties were found in the regional test,and the overall resistance was high;Seven varieties introduced showed resistance to disease susceptibility and high susceptibility,accounting for 15.91%of the overall number of varieties;Sixteen varieties in the consortium showed resistance as susceptible and highly susceptible,accounting for 10.39%of the overall number of varieties.On the whole,the corn varieties tested were at a high level of resistance to stalk rot. |
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