The Relationship Analyses Between Tea Gray Blight And Rhizosphere Microbial Community

Tea(Camellia sinensis(L.)O.Kuntze)plant is an important economic crop widely planted in China.Due to years of continuous cropping of perennial roots,frequently picking and unreasonable management mode,it has caused problems such as soil degradation and frequent occurrence of diseases and pests in tea garden.Which has seriously affected the sustainable development of the tea garden.Rhizosphere microbial community structure is not only an important evaluation index of tea garden soil quality,but also a microbial resource bank for biological control of tea plant diseases.The research on the selection mechanism of rhizosphere microbial community structure is essential to solve the above problems.In this study,taking tea garden soil as the research object,guided by the pathological problem of the tea plant,the relationship between tea gray blight and rhizosphere microbial community was analyzed by modern molecular biology methods.The main results were as follows:1.Seven strains of pathogens were isolated and purified from tea leaves with tea gray blight disease by traditional isolation and culture technology.Through morphological observation,conidial characteristics and polygenic sequence analysis,seven strains were identified as Pseudopestalotiopsis camelliae-sinensis,Neopestalotiopsis piceana,Neopestalotiopsis protearum,and Pestalotiopsis theae,respectively.According to Koch’s rule,the four pathogens can make tea pathogenic and produce the typical symptoms of tea gray blight.Among them,the strain with strong pathogenicity was Ps.Camelliae-sinensis,and the damage on tea plantation was more serious.The induced resistance and growth promotion of tea root soil damaged by tea gray blight were tested.It was found that the root soil of the tea plant seriously damaged by tea gray blight could promote the growth and reduce the disease index of tea seedlings.2.Ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)was used to analyze the root exudates of tea seedlings.The results showed that the species and abundance of compounds secreted from the roots were altered upon infection with pathogens.The metabolism of 178 compounds was down-regulated and 20 compounds were up-regulated in the root exudates of tea seedlings infected by Ps.camelliae-sinensis.Among them,paeonol,2’,4’,6’-trihydroxyacetophenone,pinobanksin,butin,epicatechin,and putrescine were less abundant in the control group,but significantly increased in the treatment group.The effect of significantly up-regulated and down-regulated compounds on disease resistance of tea seedlings was evaluated by adding exogenous root exudates.The results showed that the disease index of tea seedlings in the up-regulated compound treatment group was significantly lower than that in the control and down-regulated compound treatment group,but the difference between the groups disappeared after removing microorganisms in the soil.3.High throughput sequencing technology was used to study and analyze the soil microbial community in the root of tea seedlings.The effect of aboveground pathogen infection on the microbial community structure of rhizosphere soil was higher than that of bulk soil.Rhizosphere soil microbiome analysis revealed that rhizospheric microbial community was altered upon infection with Ps.camelliae-sinensis.Genus-level analysis showed that the fungi Pestalotiopsis,Clonostachys,Gliocladiopsis,Penicillium,Trichoderma,Saitozyma and Geminibasidium,and the bacteria Occallatibacter,candidatus Koribacter,Conexibacter,Streptomyces,Bacillus,Burkholderia and Pseudomonas were significantly increased in treatment soil.While the fungi Neodevriesia,Sagenomella,Symmetrospora,Meira and Mortierella,and the bacteria Jatrophihabitans,Niastella,Flavobacterium,Flavisolibacter,Rhizobium,Polycyclovorans,Nordella,Asticcacaulis and Rhizobacter were significantly decreased in treatment soil.More importantly,the relative abundance of Trichoderma,Penicillium,Gliocladiopsis,Pseudomonas,Streptomyces,Bacillus,and Burkholderia with biological control potential increased significantly in treatment soil.4.Rraditional culture method was used to isolate culturable microorganisms in soil,three strains of fungi Trichoderma asperellum,Gliocladiopsis irregularis,and Penicillium citrinum,,six strains of bacteria Bacillus velezensis,Bacillus subtilis,Bacillus sporothermodurans,Streptomyces ferralitis,Streptomyces olivochromogenes,and Burkholderia stagnalis were screened from rhizosphere soil of the treatment group.Through inoculation tests,the above nine strains could inhibit the infection of tea gray blight pathogen and promoted tea seedling growth.The above research shows that tea plants can recruit beneficial rhizosphere communities via modification of root exudation in response to infection to above ground pathogens.This study revealed the mechanism of tea gray blight in regulating rhizosphere microbial community,and provided reference for the study of the relationship between other diseases and rhizosphere microorganisms.A variety of beneficial microorganisms were screened from tea rhizosphere,and their ability to induce resistance was tested.It provides a theoretical basis for the development and utilization of new microbial resources,provides technical support for tea garden soil improvement and green disease prevention and control,promotes the sustainable development of tea garden,and provides a guarantee for the yield and quality of tea.