Optimization Of Fermentation Conditions For The Red Pigment Branch Of Sporidiobolus Pararoseus And Key Enzyme Gene Transcription Level Analysis

Since PGPR has been recognized by people,scholars have been very interested in its mechanism of promoting plants.Nowadays,domestic and foreign workers have conducted many studies on the mechanism of PGPR.The growth-promoting mechanism of PGPR includes nitrogen fixation,phosphorus dissolution,potassium release,hormone secretion,and biocontrol effects.Since one of the important factors affecting the biological diversity of rhizosphere microorganisms is the type of plants,and rhizosphere microorganisms are also specific to the types of plants,so in order to screen out a more suitable PGPR for the corn rhizosphere environment,use the corn rhizosphere soil Medium screening is very necessary.In this study,we selected excellent PGPR from the rhizosphere bacteria of corn,which can effectively promote the growth of corn,increase the soil environment microbial resource pool,and provide excellent strains for the future production of microbial fertilizers.The main conclusions of this article are as follows:(1)From 111 strains,40 strains with nitrogen fixation ability were screened out.The nitrogenase activity of each strain was quantitatively analyzed,and the 40 strains screened all had nitrogenase activity;the 40 strains of nitrogen-fixing bacteria were screened to determine their phosphorus-dissolving ability,in the qualitative test of phosphorus solubilization,we screened out 11 strains of inorganic phosphorus and 12 strains of organophosphate respectively;the 40 strains of nitrogen-fixing bacteria obtained from the screening were tested for potassium-resolving ability,in the potassium-resolving qualitative test,8 strains with potassium-resolving ability were screened.(2)Combining the nitrogen fixation,phosphorus solubilization,and potassium release abilities of each strain,18 strains were selected.The 18 strains were tested for their ability to secrete growth hormone(IAA).Among the final 18 strains,16 strains can secrete IAA,accounting for 88.9% of the total.Among them,Microbacterium D1-14 has the strongest IAA secretion ability.The content of IAA in the supernatant is 32.8 mg/L,which is significantly higher than other treatments.(3)Determine the siderophore secretion capacity of 40 strains of nitrogen-fixing bacteria obtained from the screening.According to the MKB-CAS double-layer plate experiment,12 strains with the ability to secrete siderophores were screened out.After further determination of sideropphore activity(Sideropphore Units,SU),it was found that the sideropphore activity in the supernatant of Atlantibacter D1-17 was the highest,Which was 33.21%,which was significantly higher than other strains.(4)Conduct pathogen antagonism experiments on 40 strains of nitrogen-fixing bacteria.The confrontation plate method was used to determine the antagonistic ability of different strains against four pathogens: Fusarium graminearum,Fusarium verticillioides,Fusarium culmorum,and Fusarium proliferatum.Finally,six strains of Pantoea D1-28,Paraburkholderia D2-1,Staphylococcus D2-23,Burkholderia D4-10,Burkholderia D4-30,Arthrobacter D4-36 were screened out with antagonistic effects,among which Burkholderia D4-10 and Arthrobacter D4-36 can simultaneously antagonize Fusarium graminearum,Fusarium verticillium and Fusarium proliferatum.(5)Combining the growth promotion and biocontrol potential of each strain,18 strains were screened out.The chemotaxis motility of these 18 strains was measured using the swimming plate method,and the results showed Pantoea D1-28 has the farthest movement distance in the 0.4% simulated semi-solid surface,but in the 0.24% agar plate,the movement distance at the same time is the shortest.(6)Combining the growth promotion and biocontrol potential of each strain,18 strains were screened out.The biofilm-producing ability of these 18 bacterial strains was determined,and finally five strains with strong biofilm-producing ability,Streptomyces Z3-46,Burkholderia D4-10,Staphylococcus D2-23,Paraburkholderia D2-1,and Arthrobacter D4-36 were screened.Among them,Paraburkholderia D2-1,Burkholderia D4-10,Streptomyces Z3-46 have outstanding biofilm production capabilities.(7)After integrating the growth promotion,biocontrol,and colonization potential of the strains,we screened out 9 strains of bacteria for pot experiment.The plant height of the seedlings treated with Pantoea D1-28 bacterial solution was the highest,16.6cm,which was7.10% higher than the control group;the Bacillus F and Paraburkholderia D2-1 treatment groups increased by 5.4% and 3.1%,respectively.Compared with the control group,the total root length,root surface area,and root volume of the Bacillus F treatment group increased by41.6%,30.4%,and 20.1% respectively,and the total root length was significantly higher than that of the control group;the Paraburkholderia D2-1 treatment group increased by 8.3%,15.6%,23.4%;Burkholderia D4-10 treatment group increased 15.1%,8.9%,2.6%.