Isolating And Application Of PGPR In Subtropical Agricultural Soil Under Salt Stress

Soil salinization has become one of the important constraints on crop yields in global agricultural ecosystems,and the use of microbial agents,such as 1-aminocyclopropane-1-carboxylic acid(ACC)Plant growth-promoting rhizobacteria(PGPR)of ammonia enzymes can enhance the salt resistance of crops.Previous studies mainly focused on the growth-promoting effect of PGPR on crops,and were mainly used in indoor pot inoculation experiments,while the application of PGPR containing ACC deaminase to field saline soil to improve the salt resistance of crops has hardly been reported.Based on this,we used the long-term salinization plot in Fengxian District,Shanghai as the research plot.By collecting saline soil samples,we screened,separated and purified PGPR containing ACC deaminase,and determined the ACC deaminase activity of the strain.To determine the high-efficiency microbial strains,construct a phylogenetic tree and analyze the genetic relationship between the strains,and use whole-genome sequencing to analyze the functional genes(acd S)of the strain's ACC deaminase.In addition,a highly effective microbial inoculum was prepared for indoor pot and field inoculation experiments to clarify the effect of the microbial inoculum on crop salt resistance.The main findings are as follows:1)A highly active strain was screened,isolated and purified from saline soil,and its ACC deaminase activity was 6.02?mol mg^-1 pro h^-1.A molecular evolutionary tree was constructed and identified as Burkholderia(Burkholderia).2)The whole genome length of this strain is 7945212 bp,and the GC content is66.603%.The function annotation results show that the functions of this strain mainly focus on transcription,catalysis,amino acid transport and metabolism.The results of the whole genome sequence analysis showed that the strain has the acd S gene,verifying that the strain has the ability to produce ACC deaminase.In addition,we also found that this strain contains functional genes related to salt resistance,indicating that this strain has a certain salt resistance potential.3)The results of indoor pot experiments show that adding the microbial agent can effectively reduce the ethylene content and increase the biomass of Arabidopsis.The results of field inoculation experiments show that the addition of inoculants can enhance the salt resistance of cabbage and eggplant.In summary,this thesis screened and obtained an efficient PGPR strain containing ACC deaminase,and prepared it into a microbial inoculum for use in indoor potting and field experiments.It was found that the strain can enhance crop salt resistance and increase crop yield.Our research results deepen the understanding of the mechanism by which ACC deaminase-containing PGPR improves crop salt resistance,and provide a theoretical basis for scientific management of saline land and sustainable agricultural development.