| Tomato(Solanum lycopersicum)is one of the main vegetables in the facilities in China.Due to the cultivating habits and economic interests,tomato is widespread in the facilities.However,the application of chemical fertilizers to soils and the salinization of the soils in the facilities,which affect the yield and quality of tomatoes,and result in the outbreak of pests and diseases,have became the main issues that restricts the development of tomato.In this study,a pot experiment was conducted in green house in the continuous cropping of tomato in phosphorus-rich soil.The cultivation mode of tomato intercroppingd with potato onion was studied,and changes in the soil available nutrient contents and the concentrations of plant nutrient contents were also analyzed to ascertain the variations of tomato nutrient uptake and distribution.The dilution plating method was used to determine the population of phosphate-solubilizing bacteria(PSB)and phosphate-mineralizing bacteria(PMB).The products were then sequenced to determine the diversities of PSB and PMB.After extracting the total genomic DNAs from the rhizosphere,the copy numbers and diversities of ALP genes were investigated using real-time PCR and PCR-DGGE,respectively.The soil bacterial and fungal communities of the tomato rhizosphere soil were studied by Miseq sequencing.Moreover,the expressions of genes related to disease resistance,content of secondary metabolism substance,the pathogenesis-related proteins activities in tomato with qRT-PCR were also assessed.The purpose of this study is to reveal the mechanisms by which intercropping with potato onion enhances the performance of tomato and alleviates Verticillium wilt of tomato from the view of allelopathy,soil microorganism and molecular biology.Overall,this study could provide theoretical foundation and technical support for the application of the potato onion as a companion crop of tomato and the reduction of the soil sickness in tomato production.It can also provide ideas and technical basis for correlation studies.Main results of this paper were as flowing:1.Intercropping with two varieties of potato onion significantly increased the plant height,shoot and root dry weight of the tomator,enhanced tomato yield by 8.49~16.92%.Moreover,intercropping with potato onion changed root morphology of tomato.The root length,root surface area,root diameter,root volume of tomato intercropped with potato onion were increased significantly,and there are differences between the two varieties of potato onion.2.Tomato intercropped with variety potato onion increased N,P,K,Mn,Mo content distribution ratio in root of tomato,increased P,K,Mn,Mo,B,Si content distribution ratio in flowers and fruit of IV tomato,but tomato intercropped with variety potato onion decreased N,P,K,Mn,Mo,B,Si content distribution ratio of leaf of tomato.Intercropping with potato onion changed nutrient distribution of tomato,decreased nutrient distribution ratio in leaf of tomato,increased nutrient distribution ratio in root and fruit of tomato and enhanced tomato nutrient utilization.3.The chlorophyll content of intercropped tomato was higher than that of monocultured tomato at 23 d.The biomass and root activity of intercropped tomato increased significantly than that of monocultured tomato at 23 d,30 d and 37 d,but the opposite trend was obtained for potato onion seedlings.Therefore,these results implied that interspecific competition and interspecific promote occurred at the same time.The intercropping improves the growth of tomato but restrains that of potato onion.4.The activities of soil dehydrogenase,urease and polyphenol oxidase in the tomato intercropping rhizosphere are increased significantly.The activities of alkaline phosphatase in the tomato intercropping rhizosphere increased significantly at 23 d,the activities of soil catalase in the tomato intercropping rhizosphere are increased significantly at 37 d compared to monocultured tomato.The contents of soil available nitrogen,phosphorus,potassium,available manganese,available silica and available boron in the tomato intercropping rhizosphere decreased significantly.Intercropping with potato onion may also improve soil ecological environment by lowering levels of soil acidification and salinization,and promote the nutrient uptake of tomato intercropping.5.The copy number of PSB,PMB and ALP gene in the soil of the intercropped tomato was higher than that of the monocultured tomato,the Shannon diversity and Evenness indexes of the PSB,PMB and ALP gene community were higher in the intercropped soil of tomato.Furthermore,the relative abundances of Pseudomonas,Rhizobium Bacillus,and Sphingobium increased in tomato rhizosphere in the intercropping system.In conclusion,tomato intercropping with potato onion increased phosphobacteria diversity and function,and improved soil phosphobacteria transformation.6.Tomato intercropping with potato onion affected tomato rhizosphere soil bacteria and fungi community structures.Intercropping with potato onion increased the abundances of Actinobacteria,Bacteroidetes,Flavobacteria,Chlorobia,Chloroflexi,Anaerolineae,Deinococci,Gemmatimonadetes,Clostridia,Mollicutes,Planctomycetacia,Alphaproteobacteria and Opitutae,but decreased the abundances of Dothideomycetes,Eurotiomycetes,Discomycete,Leotiomycetes,Tremellomycetes,Agaricomycetes,Microbotryomycetes and Chytridiomycetes.Moreover,the relative abundances of Pseudomonas,Rhizobium,Bacillus and Sphingobium increased in the rhizosphere of tomato in the intercropping system at the genus level.For fungi,the relative abundances of Penicillium,Aspergillus and Chaetomium increased,but decreased abundance of Eurotium and Thielavia in the rhizosphere of tomato in the intercropping system.7.In the anatomical structure of root and stems of tomato intercropping cell organelle remains integrated.and starch grains accumulates largely in the chloroplasts.But,in the anatomical structure of root and stems of tomato intercropping cell organelle were badly damaged,and starch grains accumulates largely in the chloroplasts,and increased osmiophilic granules.Intercropping with potato onion increased the activities of PAL,PPO,POD,chitinase,?-1,3-glucanase,the contents of flavonoid,total soluble phenolics and lignin contents,and decreased the MDA contents in tomato roots.8.Inoculation of Verticillium wilt induced genes involved in shikimate–phenylpropanoid–lignin pathways in the tomato roots in both intercropping and monoculture systems.However,the timing and levels of the induced expressions differ between the two cropping system.In the intercropping system,PAL,C4 H,4CL,CCR,CAD genes were strongly induced during the early stages of Verticillium wilt infection and the expression levels were higher by 2~16 times compared to the monoculture.In the intercropping system,Chi-E,Glu-E,NPR1,PR-1,CHS and CHI genes were strongly induced during the early stages of Verticillium wilt infection and the expression levels were higher than that in the monoculture system.Overall,tomato intercropping with potato onion promoted the growth of tomato but inhibited that of potato onion.Changes of the root surface area,root volume and root activity of tomato seedling in intercropping,were beneficial for mineral nutrient uptake.Intercropping with potato onion changed nutrient distribution of tomato,and enhanced tomato yield.The activities of soil dehydrogenase,urease and polyphenol oxidase in the intercropped tomato rhizosphere increased significantly.The copy number and diversity of PSB,PMB,and ALP gene in the soil of the intercropped tomato was higher than that of the monocultured tomato.Intercropping with potato onion may also improve soil ecological environment by lowering levels of soil acidification and salinization.Intercropping with potato onion changed bacteria and fungi community diversity in the tomato rhizosphere,and improved abundance of Pseudomonas,Sphingomonas,Penicillium,Aspergillus and Chaetomium,but decreased the abundance of Eurotium and Thielavia in the rhizosphere of tomato in the intercropping system.Intercropping with potato onion increased the activities of PAL,PPO,POD,chitinase and ?-1,3-glucanase,and the content of flavonoid,total soluble phenolics and lignin contents,and decreased MDA contents in tomato roots.In the intercropping system,pathogenesis-related protein genes and flavonoids synthesis related genes genes were strongly induced during the early stages of Verticillium wilt infection and the expression levels were higher than in the monoculture system.The contents of total lignin,total phenols,flavonoids and pathogenic proteins(chitinase and ?-1,3-glucanase)and POD PPO,PAL and other defensive enzymes activity,which response to a series of resistance at molecular and physiological level,were increased by regulating the expression of genes related to secondary metabolites synthesis,and thus improved tomato resistance to Verticillium wilt. |
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