Study On The Relationship Between Rhizosphere Microorganisms And The Root-knot Nematodes Occurrence In Tobacco And Its Regulation

Tobacco root-knot nematode disease is a soil-borne tobacco disease caused by plant-parasitic root-knot nematode infection.Under long-term continuous cropping cultivation mode,tobacco root-knot nematode disease is increasing every year in major tobacco regions of the country.Because of its special infectivity,tobacco farmers often do not pay enough attention,and the timely prevention and control of field diseases often results in a large amount of economic losses.Traditional prevention and control methods often use chemical agents,which are not very targeted,and cause problems such as environmental pollution,pesticide residues,and drug resistance.With the continuous deepening of scientific research,people have gradually realized the science and necessity of prevention and control of the disease.If you want to prevent and control the disease thoroughly,you must first understand the key to the disease and find the cause of the disease for targeted treatment.With the continuous deepening of research in recent years,people pay more attention to the mechanism of microecological action in soil and the relationship between microorganisms.To this end,this article analyzes the relationship between tobacco root-knot nematode-infected soil and healthy soil,finds the differences between microorganisms,and then combines high-throughput sequencing and ECO to diversify the microbial community under biocontrol treatment conditions.Comprehensive and systematic analysis of sexuality and metabolic diversity,the main research results are as follows:1.The decrease of soil pH and the increase of total N and P increased the occurrence of tobacco root-knot nematode disease.The physical and chemical properties of tobacco root-knot nematode disease and healthy rhizosphere soil were tested.The contents of soil pH,total N,and total P content were different between tobacco root-knot nematode disease and healthy soil.Among them,the decrease of pH is more conducive to the aggravation of the disease.2.The key to the occurrence of tobacco root-knot nematode is the change in the diversity of soil microbial community structure.By analyzing the microbial composition of diseased and healthy soil samples,we found that the microbial composition groups in healthy soil samples were more abundant than those in diseased soil.protruding.At the same time,it was found that there are more different microbial groups in healthy soil,and they contain a lot of beneficial microorganisms.Pseudomonas is among the top 21 genera in healthy soils with an LDA value of 2.87,a relative abundance of 0.16% in healthy soils,and a relative abundance of only 0.02% in diseased soils.3.The occurrence of tobacco root-knot nematode is closely related to the microorganisms in five species.Among the microbial groups that are key to the occurrence of tobacco root-knot nematode disease,Pseudomonas has a negative correlation with the occurrence of tobacco root-knot nematode disease in healthy soils;in the affected soils,Bryobacter,Variibacter,Coniochaeta,and Metahizium were positively correlated with the occurrence of tobacco root-knot nematode.Studies have shown that the addition of exogenous biocontrol bacteria can effectively change the community structure of rhizosphere microorganisms.We found that five types of microbial groups play an important role in disease occurrence.4.Clarified the main types of carbon sources for functional diversity of rhizosphere microbial communities.Adding biocides to the soil can promote the overall use of carbon sources by the soil microbial community and enhance the metabolic activity of the carbon source by the microorganisms;it can also increase the species diversity of the soil microbial community and increase the dominance and uniformity of the microbial species.Carboxylic acids and amino acids are the main types that cause differences in the metabolism of carbon sources by microorganisms.7 metabolic carbons: ?-methyl D-glucoside,D-galactonic acid-?-lactone,I-erythritol,D-cellobiose,L-serine,itaconic acid,and D-malic acid The use of sources plays an important role in disease prevention and control.Paecilomyces lilacinus plays a key role in disease prevention and control by promoting the metabolism and utilization of carbohydrates(D-galactosyl-?-lactone)by microorganisms.5.The effects of biocontrol bacteria on the occurrence of tobacco root-knot nematode disease,anti-stress enzyme activity and tobacco growth were verified.Bacillus subtills,Pseudomonas fluorescens and Paecilomyces lilacinus can reduce the number of second-instar larvae of root-knot nematodes,reduce the number of root knots in tobacco plants,and reduce the incidence of root-knot nematode disease in tobacco.From the perspective of prevention and control effects,the three can reach 56.73%,82.97%,and 88.90%,respectively.Biocontrol bacteria treatment can also enhance the activities of peroxidase(POD),catalase(CAT),polyphenol oxidase(PPO),enhance resistance to tobacco stress,and promote the growth and development of tobacco plants.In addition to the maximum leaf length,the plant height,stem circumference,effective leaf number,and maximum leaf width of the treatment with Paecilomyces lilacinus were the largest increases of 44.91%,20.11%,11.78%,and 39.05%.To sum up,Pseudomonas has great potential in suppressing disease occurrence;Paecilomyces lilacinus has a very good effect in field disease control;the occurrence of tobacco root-knot nematode disease is closely related to the changes of rhizosphere microorganisms directly or indirectly.