Screening Of Plant Growth Promoting Strains And The Mechanism Of Volatile Organic Compounds From Microbacterium Aurantiacum On Plant Growth Promotion

With the implementation of the double reduction policy of chemical fertilizer and pesticide,the research and development of microbial fertilizer has become the focus of agricultural sustainable development.Microbial fertilizer contains one or several beneficial living microorganisms.With the help of its metabolic process or metabolites,it can promote plant growth.The screening of excellent plant growth promoting strains is an important part and foundation.The production of volatile organic compounds（VOCs）is an important way for strains to promote plant growth.In this experiment,a dominant strain GX14001 producing VOCs was screened by I plate experiment,and its taxonomic status was clarified.The biological activities of VOCs produced by strain GX14001 on the tobacco were measured.The growth promoting mechanism was explored by combining transcriptome sequencing with Arabidopsis mutants.The main components of VOCs produced by GX14001 were further studied by GC-MS.The whole genome draft of GX14001 was determined,and its potential other functions were explored.The other growth-promoting and biocontrol functions of the initially screened strains which produce VOCs that promote plant growth were explored,and the pot experiment of tomato（Lycopersicon esculentum M.）was carried out.The main results are as follows:1.71 strains of VOCs were screened by a plate divided into two sections（I-plate）experiment,and the volatile organic compounds released by them showed obvious promoting effects on tobacco（Nicotiana benthamiana L.）leaves,fresh weight,root length and lateral root number.After rescreening and comprehensive analysis,a dominant strain GX14001 producing growth-promoting VOCs was obtained,and a pot experiment was carried out,the results showed that the volatile organic compounds produced by GX14001 can significantly promote the growth of tobacco and pakchoi（Brassica chinensis L.）.2.The taxonomic properties of strain GX14001 were clarified.The GX14001 was identified as Microbacterium aurantiacum through 16 S r RNA gene sequence homology comparison and physiological and biochemical characteristics analysis.3.Transcriptome sequencing and Arabidopsis mutants verification experiments were carried out on GX14001-VOCs-promoted tobacco to explore the signal pathway and mechanism of GX14001-VOCs on tobacco growth promotion.The results showed that volatile organic compounds produced by Microbacterium aurantiacum GX14001 might promote the growth of tobacco through auxin,salicylic acid and gibberellin.4.The volatile organic compounds produced by GX14001 were analyzed by Gas Chromatography-Mass（GC-MS）,and it was clear that the main promotion of volatile organic compounds produced by GX14001 was divided into dodecane and pentacosane.5.The whole genome draft of GX14001 was determined by highthroughput sequencing technology.Through genomic informatics analysis,it was found that Microbacterium aurantiacum GX14001 had potential degradation of p-Hydroxybenzoic acid（PHBA）,and this function was preliminarily explored.6.The preliminary screened production of promoting VOCs strains were investigated for their nitrogen fixation,phosphorus solubilization,potassium solubilization,IAA production,life-promoting activity,ferrophilic carrier,and antagonistic activity against plant pathogenic fungi.Subsequently,tomato greenhouse pot experiments were conducted on the obtained strains with excellent activity.The results showed that Bacillus altitudinis,Bacillus tequilensis,Bacillus flexus,Bacillus paralicheniformis and Microbacterium aurantiacum could promote the growth of tomato plants through different aspects.These five strains have the potential as agricultural applications.Based on the comprehensive analysis,Bacillus sp.was the dominant strain of plant growth-promoting bacteria,which had the potential of growth promotion and biocontrol.