The Effect Of Tobacco Bacterial Wilt On The Rhizosphere Soil Microecology Of Tobacco

Soil microbial ecology,a relatively new branch of ecology,mainly studies relationship between soil microorganisms and the environment.Due to the huge quantity of microorganisms in the soil and their complex functions,scholars at home and abroad have studied soil microorganisms with new technologies such as macro genome high flux sequencing.However,very few of these researches focus on the interactions between soil and microbial system.Even fewer studies are devoted to the comparison of soil microbial ecologies when plants are healthy and when they are not.Shaowu is the main tobacco growing area in Fujian province with two types of soil for tobacco planting light loam and sandy soil.The tobacco planting here is seriously affected by the bacterial wilt.This study has sampled the two tobacco plant rhizosphere soil for three consecutive years since 2014 so as to examine the differences in soil properties indexes,such as physical and chemical indicators,trace elements,enzymes,green dry reye's bacteria numbers,soil bacterial community structure and diversity,and soil fungal community structure and diversity under three conditions:healthy plants,early stages of bacterial wilt,and middle stages.The relationship between soil properties and soil microorganisms is also analyzed.The main results were as the following:1.Light loam and sandy soil have great differences in soil properties index values:the total carbon,organic carbon,total nitrogen,alkaline hydrolysis n,available k,available p,Ca,Fe,Mg,beta glycosidase enzymes,acid phosphatase,and sucrose invertase in sandy soil is generally lower in their amounts than those in light loam soil.It is shown that the sandy soil is relatively poor with fewer nutrients and its water-retention capacity is poor.The study of tobacco plants in the same soil under three conditions show similar differences in the soil indexes obtained from the testing dong for three consecutive years.It shows that under rotation,planting time and can't change the larger degree change of soil properties.In both of the two types of soil,pH,the contents of organic carbon,alkaline hydrolysis n,available p,Ca,Fe,beta glycosidase enzymes,urease,acid phosphatase,sucrose invertase content are as follows:health tobacco plant rhizosphere>mild pathogenesis rhizosphere soil>medium of tobacco plant rhizosphere soil of tobacco plant,total carbon content in the soil of tobacco plant health>moderate soil>mild disease incidence trend of soil.In addition,total n,available k,Mg,Mn,Cu and trend of the content of hydrogen peroxide enzyme showed the differences in the two kinds of soil.These differences between bacterial wilt disease under light loam and sandy soil indicators are worthy of attention.2.Principal component analysis is adopted to construct the comprehensive evaluation models of soil properties in the two types of soil under three conditions.The evaluation model pointed out that the contribution of various soil indexes to the formation of soil properties and stability under this condition.By comparing the normalized weighting coefficients,the model is obtained regarding to the importance sequencing of the 17 kinds of soil properties indexes.Comparison revealed that the importance of soil properties were different in of light loam and sandy soil and the importance of urease,total nitrogen,catalase and other indicators were similar.There is a significant difference between the soil property indexes in healthy plants and diseased plants,indicating that the incidence and severity of the bacterial wilt disease have a lot to do with the soil.3.The use of SYBR green I fluorescence quantitative PCR determination of withered reye's bacteria showed that the contents of wilt reye's bacteria have reached 106 in the mature period of healthy tobacco plants,107 in the early stage of bacterial wilt,and 108 in the middle stage of wilt.It shows that the severity of bacterial wilt is in direct relation to the contents of wilt reye's bacteria.4.173,453 gene sequences and 188,470 gene sequences were obtained by amplification 16S rDNA through high-throughput sequencing from light loam soil samples and sandy soil samples respectively.Comparing soil bacterial diversity indexes,Rank-Abundance curve and dilution curve under 3 conditions has found the health plants have the highest soil bacterial richness and diversity,followed by tobacco plants at the early stage of bacterial wilt and those at the middle stage of the disease.Analysis of bacterial community structure,light loam and sandy soil samples in the classification level of health,smoke root soil Actinobacteria,relative abundance of Bacteroidetes were greater than tobacco plant disease,the bud door Gemmatimonadetes,nitrification bacterium spirillum door Nitrospirae relative abundance were less than the onset of strain;In the level of the classification,the relative abundance of Norank_p_Saccharibacteria decreased incidence of tobacco plant,and Bacillus,to the contrary,account number Norank_p_Saccharibacteria negatively correlated with the incidence of tobacco bacterial wilt,and the number of Bacillus were positively correlated with the incidence of tobacco bacterial wilt.5.Through the amplification of soil samples 18S rDNA and high-throughput sequencing,159,439 gene sequences were obtained from the light loam samples,and 137,058 gene sequences were obtained from the sand samples.Respectively to compare three kinds of condition of soil fungal diversity index,Rank-Abundance curve and dilution curve,light loam found moderate soil fungi community richness of tobacco plant disease is highest,mild soil fungi community diversity of tobacco plant disease,the best health soil community evenness of tobacco plant;In the sand soil,the soil fungus community richness and diversity were the best,and the soil fungus community was the best.Fungal community structure were analyzed,and the level of the classification,door light loam and sandy soil Unclassified_d_Eukaryota relative abundance sort:tobacco plants,the moderate disease>>disease health and Basidiomycota relative abundance in the various groups to include:the health>mild disease>moderate incidence of tobacco plant,the two species,and play a certain role in the incidence of tobacco bacterial wilt.6.Correlation analysis was used to investigate the relationship between soil properties and microorganisms.By dimension reduction,can represent part of soil property indexes,through the analysis of the differences between groups,microbial characteristic indexes,two types of indicators to correlation analysis found that(1)the correlation of fungi and soil properties index is lower than bacteria,importance in maintain soil microecological bacteria than fungi.(2)in the two types of soil,soil properties index is the key influencing factor of soil microorganisms:the root of healthy tobacco plant is the total nitrogen and urease;The rhizosphere soil of the mildly infected tobacco plant was quick acting potassium and Cu.The rhizosphere soil of moderate onset tobacco plant was rapid phosphorus.7.The relationship between soil properties and microorganisms and samples was investigated by means of redundant analysis.In the analysis of soil bacteria,the quick effect potassium,total nitrogen and Mn of the light loam separated the healthy tobacco plant soil from the soil area of the mild disease.Fe,acid phosphatase,urease,and quick-acting phosphorus separated the soil of the healthy tobacco plant from the soil of the medium.The Cu and urease of sandy soil separated the soil samples from the healthy tobacco plant.Alkali-nitrogen,total nitrogen,Ca,beta-glucosidase,organic carbon,quick-acting potassium,urease,etc.,separated the healthy tobacco plant soil from the soil sample of the moderately infected tobacco plant.On the analysis of soil fungi,light loam of catalase,Mg,available k,acid phosphatase,pH,and beta-glycosidase enzymes to mild soil of tobacco plant disease and healthy soil of tobacco plant and moderate soil samples of tobacco plant disease.Hydrogen peroxidase,total nitrogen and alkali-nitrogen were separated from the soil samples of the healthy tobacco plant soil and the moderately developed tobacco plant.The MMG,Fe,Mn,sucrose invertase,Ca,quick-acting phosphorus,alkaline nitrogen and acid phosphatase were used to separate the soil samples of the healthy tobacco plant.The soil samples of the healthy tobacco plant were separated from the soil samples of the moderate pathogenesis of the tobacco plant,including the glucosidase,Mg,alkali solution nitrogen,invertase,Ca,organic carbon,acid phosphatase,etc.