Study On The Microecological Mechanisms And Regulation Of Tobacco Root Rot

Tobacco root rot is a soil-borne disease caused by Fusarium infection.It occurs in most tobacco producing areas in China,causing serious losses to tobacco production.Soil microbes are one of the key ecological factors affecting the occurrence of soil-borne diseases.Adjusting the composition of soil microbial communities and increasing the abundance of beneficial microorganisms is an important means to control soil-borne diseases.At present,the research on the biological control of soil-borne diseases mainly focuses on the interaction between plants,pathogens and biocontrol bacteria,while ignoring the role of microbial groups/communities in the rhizosphere of plants,resulting in unstable field control effects.At this stage,the key ecological factors affecting the occurrence of tobacco root rot are still unclear,and the mechanism of action of beneficial microorganisms is mainly focused on the production of antibiotics,induction of systemic resistance,promotion of plant growth or interference with pathogenic bacteria,and beneficial microorganisms.The role of rhizosphere microecological changes is not clear.Therefore,on the basis of clarifying the rhizosphere micro-ecological characteristics of tobacco root rot,the key ecological factors affecting the disease are found,and then,by coordinating soil nutrition and using beneficial microorganisms to regulate the rhizosphere micro-ecological balance,it is especially important for effective prevention and control of tobacco root rot.This paper mainly analyzes the microecological characteristics of tobacco root rot and healthy soil,and identifies the key micro-ecological factors affecting the occurrence of tobacco root rot.Screening and evaluation of beneficial microorganisms with significant antibacterial and disease-preventing effects,and analyzed The effects of beneficial microorganisms on soil microbial community composition,and the technical methods to control tobacco root rot by regulating rhizosphere microecology were explored to provide support for the prevention and control of tobacco root rot.1.It is clear that there are differences between tobacco root rot and healthy soil ecological factors.By detecting the occurrence of tobacco root rot and the physical and chemical properties of healthy soil,soil pH may not be a key ecological factor affecting the occurrence of tobacco root rot,but soil alkaline nitrogen content is too high,copper and iron missing plots,root rot occurs more seriously.Biolog ECO microplate method was used to detect the occurrence of tobacco root rot and healthy rhizosphere soil microbial metabolic activity.The results showed that the metabolic activity of microbial carbon source in rhizosphere soil of healthy tobacco was significantly different from that of diseased tobacco.Mainly in the metabolic activity of esters,carboxylic acids,amino acids,there are significant differences,and this difference is more and more significant with the increase of continuous years.2.Analysis of tobacco root rot and healthy rhizosphere soil microbial community composition and dominant microorganisms.The 16 S rRNA and ITS high-throughput sequencing technology was used to detect the bacterial and root fungal community composition of tobacco root rot and healthy rhizosphere soil.The study found significant differences in bacterial and fungal community composition between diseased and healthy samples.Analysis of key microorganisms affecting the occurrence of tobacco root rot found that the relative abundance of Fusarium in the healthy samples was significantly lower than that of the diseased samples.The bacterial community of Actinoplanes and Sphingomonas,Lysobacter,etc.,and the fungal community of Penicillium,Phialemonium,etc.in the healthy rhizosphere are significantly higher than the onset rhizosphere.3.Explore nutrients that are significantly associated with dominant microbes.Analysis of the relationship between microbial communities and environmental factors by calculating the Spearman rank correlation coefficient between environmental factors and selected species.The results showed that the dominant microorganisms indicating tobacco root rot,such as Fusarium and Rhodococcus,were significantly positively correlated with the contents of alkali nitrogen,available chlorine and exchangeable calcium in soil,and there was a significant negative correlation between available phosphorus,available copper and available iron.However,the dominant microorganisms indicating the state of health,such as Penicillium,Lysobacter,etc.,exhibit opposite correlation results.4.Screening microorganisms that have inhibitory effects on pathogens: Trichoderma harzianum and Paenibacillus polymyxa,and evaluated the antibacterial and preventive effects of two microorganisms.Two kinds of microorganisms with high antagonistic activity against pathogenic bacteria and good control effect on tobacco root rot were screened by flat-panel confrontation,indoor potting and field verification experiments: T.harzianum and P.polymyxa.After 8 days of inoculation of pathogens,the indoor control effect of the two microorganisms on root rot reached 55.42%~73.76%.At the peak of field incidence,the incidence and disease index of tobacco root rot could be significantly reduced.5.The effects of two microorganisms on the microbial community composition of tobacco rhizosphere soil were studied,and the key microbial groups that regulate the rhizosphere microbial community by two microorganisms were identified.The 16 S rRNA and ITS sequencing techniques were used to analyze the differences in bacterial community composition of rhizosphere soils of T.harzianum,P.polymyxa and control.The results showed that after treatment with P.polymyxa and T.harzianum,actinobacteria increased by 5.27% and 2.90%,respectively.The relative abundance of Ascomycota increased by 6.53% and 11.38%,respectively,compared to the control.Compared with the control,P.polymyxa and T.harzianum treatment significantly reduced the relative abundance of Fusarium,which was reduced by 8% to 10%.LEfSe analysis was used to screen the dominant microbial population under the control of birth control,and the Venn diagram was used to screen key microbial groups.The results show that compared with the control,both T.harzianum and P.polymyxa significantly increased the relative abundance of Lysobacter,Sphingomonas and Gemmatimonas in the rhizosphere,and it inhibits the relative abundance of Rhodococcus and Fusarium.6.The field control effect of microecological regulation on tobacco root rot was verified.A series of micro-ecological control techniques,such as balancing soil nutrients and improving soil microbial structure,were tested in five-year continuous root rot high-risk plots.The results showed that microecological regulation can significantly delay the occurrence of root rot in the field and reduce the incidence of root rot in the field.At the peak of the disease,60.42% of the relative control effect can be obtained compared with the control.In summary,the occurrence of tobacco root rot is closely related to the specific rhizosphere soil ecological factors.Both T.harzianum and P.polymyxa inhibited the growth of pathogenic bacteria and had significant control effects on tobacco root rot.At the same time,the addition of biocontrol microorganisms can significantly increase the number of beneficial microorganisms in the rhizosphere,inhibit the abundance of pathogenic bacteria,and promote the development of rhizosphere soil micro-ecological environment to health..