Research On The Response Law Of Tomato Rhizosphere Microorganisms To Adversity And Resource Development

Rhizosphere microorganisms refer to microorganisms that are tightly attached to soil particles in the rhizosphere.The rhizosphere microbiome is called the "second genome" of plants.The two have co-evolved and have a significant regulatory effect on the yield and quality of agricultural products.Highly resistant plants secrete a large number of microbial cell wall hydrolyzed proteins such as chitinase,which catalyze the hydrolysis of chitin to generate N-acetylglucosamine,etc.,which limit the growth and reproduction of pathogenic microorganisms,opportunistic pathogenic microorganisms and symbiotic microorganisms,and affect crops and bacteria.The microbial inoculants establish a symbiotic relationship,resulting in problems such as unstable efficacy after field application of microbial inoculants.Under biotic stress conditions,the communication and interaction between microorganisms and plants is worthy of further study.In this paper,chitin and its derivatives were used to simulate the stress environment of highly resistant plants,and tomato(Solanum lycopersicum)plants were used as research materials to explore the regulation of tomato rhizosphere microorganisms on the balance of tomato growth and resistance.Using high-throughput sequencing technology(Next Generation Sequencing,NGS)to study the changes in the composition of plant rhizosphere microbial communities under simulated biotic stress conditions of chitin and its derivatives,and to screen dominant rhizosphere microorganisms that can promote plant growth and biological control effects strains,reveal the response mechanism and adaptation mechanism of rhizosphere microorganisms under biotic stress conditions,and conduct research with the goal of developing new microbial inoculants or optimizing the formulation of microbial inoculants.The main findings are as follows:(1)Chitin,chitosan oligosaccharide and N-acetylglucosamine were selected to treat tomato plants,and it was found that the three components had certain growth promoting ability.Tomato plants treated with small molecule chitosan oligosaccharide and Nacetylglucosamine showed higher plant height,total fresh weight and stem weight,which were 1.29 times higher than those treated with water.Comparing the growth parameters of chitosan oligosaccharide and N-acetylglucosamine,chitosan oligosaccharide and Nacetylglucosamine did not promote the growth of tomato,indicating that chitosan and its derivatives could promote the growth of tomato rhizosphere microorganism,weaken the resistance of plant and alleviate the stress of rhizosphere;(2)High-throughput sequencing technology was used to analyze the microbial diversity of the field soil,rhizosphere soil,and microbial samples in the roots around tomato roots after treatment with chitosan oligosaccharide and N-acetylglucosamine.It was found that chitosan oligosaccharide and N-acetylglucosamine treatments were beneficial to the root formation of more attractive soil microenvironment,and to the enrichment and propagation of various microorganisms.Compared with the soil in natural conditions,N-acetylglucosamine treatment greatly promoted the enrichment of Proteobacteria and Actinobacteria,and Chitooligosaccharide treatment recruited the more abundant Proteobacteria and Bacteroidetes,changing the Metabolic pathways of the microbiome,indicating that as highly resistant plant stress mimics,chitin and its derivatives can promote plant growth by regulating microbial community structure and metabolism;(3)Six rhizosphere microorganisms were isolated and purified from the rhizosphere soil of tomato plants treated with N-acetylglucosamine,and identified by 16 S r RNA sequence as Bacillus cereus(Sp-1),Proteus mirabilis(Sp-7),Pseudomonas monteilii(Sp-8),Streptomyces thermocarboxydus(Fs-1,CGMCC 21628),Streptomyces spinoverrucosus(Fs-2)and Streptomyces mexicanus(Fs-3).Compared with the control group,all 6 strains improved the height of tomato to some extent,especially Sp-1,Fs-1,Fs-2 and Fs-3,and all of them promoted the development and elongation of lateral roots;(4)N-acetylglucosamine was used as a representative substance to study the mechanism of its interaction with rhizosphere microorganisms on plant growth.It was found that high concentration of N-acetylglucosamine can hinder the fermentation process of microorganisms,and the addition concentration of 40 mmol/L is the best;Nacetylglucosamine could activate the ability of microorganisms to synthesize auxin IAA;volatile organic compounds(VOCs)were detected by GC-MS,and N-acetylglucosamine treatment increased the biosynthesis of acetyl and 2,3-butanediol,which can promote the growth of plants;(5)A kind of Streptomyces thermocarboxydus and its synergistic biological agent were preliminarily prepared in this paper.Streptomyces thermocarboxydus,N-acetylglucosamine and Bacillus subtilis were selected by Plackett-Burman test to prepare microbial inoculants.Compared with the control group without addition,the tomato treated with microbial inoculants showed better plant growth,yield and quality indicators.