Studies On The Growth Promotion Of Maize Induced By Bacillus Amyloliquefaciens YM6 Under Salt Stress And Its Mechanisms Of Salt-tolerance

Soil salinization seriously affects the sustainable development of agricultural economy in China.It was found that several special rhizosphere or endophytic microorganisms interact with plants to effectively improve the salt tolerance of plants.Bacillus amyloliquefaciens YM6 was isolated in our laboratory,which significantly increased the maize's tolerance to salinity.The effects of YM6 on the growth of maize under salt stress was examined.It revealed that some oligopeptides might have connection with salt stress by metabonomic analysis.Transcriptomics was carried out to elucidate the mechanisms of salt tolerance conferred by oligopeptide.The main results were showed as follows:1.In hydroponic cultivation,it was confirmed that YM6 significantly increased maize plant height?15.2%?,root length?22.3%?and stem diameter?5.2%?.The yield of silage corn inoculated with YM6 was increased by 35.7%compared to the non-inoculated control.It also indicated that YM6 could utilize starch,solubilize phosphate,produce IAA,and inhibit some common plant pathogens such as Fusarium oxysporum f.2.Inoculation of YM6 could alleviate the salt stress-induced damages of sub-cellular structures in the root tip.YM6 could also affect the content increasing of proline,K⁺and Ca²⁺in plant tissue.The enzymatic activity that the maximum SOD was 282.28 U/g·FW,CAT was 271.9 U/g·FW and POD was 742.72 U/g·FW,lower Na⁺content by 0.99g/kg and enhance the K⁺/Na⁺20.6%in plant tissue,repectively.3.Metabonomic analysis indicated that there were 60 metabolites showed differences between YM6-treated and non-treated plants.According to KEGG functional pathway analysis,we found that YM6 could induce maize plant synthesizing osmotic regulating amino acids,accumulating flavonoid antioxidants,and so on.4.Among the differential oligopeptides,Arg-Gln-Arg-Gly was chosen to test the effect of inducing maize to tolerate salt stress.The results investaged that this oligopeptide could promote maize growth under salt stress condition.The optimal concentration of the oligopeptide was 1x10^-7mol/L to 1×10^-8mol/L.However,it was added at the concentration from 1x10^-33 mol/L to 1x10^-44 mol/L,which demonstrated strong inhibitory on maize growth?p<0.05?.Transcriptomics and metabolomics were used to explore the mechanisms of oligopeptide to mitigate salt stress on maize.The oligopeptide involved in osmotic regulation,amino acid metabolism,energy generation,antioxidant production,signal transmission and cellular components synthesis.It also took part in purine pyrimidine metabolism,carotenoid synthesis,and linoleic acid metabolism.This study showed that both Bacillus amyloliquefaciens YM6 and the oligopeptide Arg-Gln-Arg-Gly could promote the growth of maize under salt stress conditions.The mechanisms of salt stress relief were based on the regulation of substance metabolism,ion balance and antioxidant metabolism.It was obvious that YM6 and oligopeptide had the great potential in the maize production in the saline soils.