Correlation Between Microenvironments And Bacterial Communities And Function In The Rhizosphere Of Camellia Sinensis

Tea is an important economic plant in the southern subtropical region of China.Acidification of soil is an important factor reducing the quatity and quality of tea as well as causing continuous cropping obstacles.In order to study the causes of soil acidification and its effect on microbial population and functional diversity in tea plants,the physical and chemical characteristics,bacterial and functional diversities of rhizosphere soil were analyzed.The relationship between physical,chemical and bacterial properties is also analyzed.These results might provide guidance for soil remediation in tea garden and the development of green and healthy planting technology for tea plants.First,the main physical and chemical properties of rhizosphere soil from tea plants were analyzed.The results showed that significant difference of pH value existed between different soils,with range of 4.05-5.08.The pH value of KSM02,KSC01 and KSCX02 was lower than 4.5,while KSS01,KSH01,KSM01,K01 and KSC02 had pH value higher than 4.5.The contents of OM,N,P,K,Na,Mg and Ca were significant between soils,with the highest content for OM(8377-32231 mg/kg)and Na(5091-5171mg/kg).The contents of Mn,Fe,Zn,Al and Pb were significant between soils,with the highest content for Al(120-584 mg/kg).The relationship between pH and K,Na,Fe,Zn,Pb and Al was negative,while the pH value was negatively correlated with K(p<0.01)and Al(p<0.05).Secondly,the diversity of bacterial populations in the rhizosphere soil of different tea plants was analyzed based on Illumina Miseq.The richness and diversity of the sample KS01 were highest,followed by KSS01,KSM01,KSC02,KSH01,KSCX02 and KSM02,and KSC01 was the lowest.Proteobacteria and Acidobacteria were the dominants in the rhizosphere soils,followed by Actinobacteria.Proteobacteria was the largest in the sample KSC01(43.37%),and Actinobacteria was the largest in the sample KSH01(36.18%),and Actinobacteria was the largest in the sample KSM02(13.68%).The ratio of Proteobacteria vs Acidobacteria was less than 1 were found in soils of KSM02,KSM01 and KS01.The abundance of Gp2 was the largest(10-25%)in different soils,followed by Gpl(1.49-9.89%)Gp3(0.75-5.53%)and Gp13(0.42-5.40%).The environmental factors,pH,P,K,Na,Fe and Al,had the greatest influence on the distribution of Acidobacteria community,among which the pH value is particularly prominent,followed by Al,P,K and Fe.The main effects on the community distribution of Proteobacteria were of pH,K and Pb.Thirdly,the functional diversity of bacteria in rhizosphere soil of different tea plants was analyzed.The metabolic ability of different carbon sources for bacteria in the rhizosphere of tea plants was studied based on Biolog Eco microplate technique.KSC02 showed the highest AWCD value and McIntosh index,followed by KSM01 and KSCX02,with KSS01 as the lowest.Microbes in soil KSM01 had the strongest ability to utilize polymer and phenolic acid,and KSC02 had the strongest ability to utilize carbohydrates and amino acids.KSCX02 was poor to use all the carbon sources.Finally,the degradation activity of phenolic acid by rhizosphere bacteria of tea plants was studied.Ten bacteria degrading phenolic acid were obtained from the rhizosphere soil of tea plants.Seven of them belong to Bacillus,and one belong to Citrobacter,Lysinibacillus and Paenibacillus,respectively.Strains B2,B1-2 and B1-6 showed the highest degradation rate of coumaric acid,ferulic acid and cinnamic acid.Strains B2,B1-2 and B1-6 protected the peanut seeds from stresses of the four phenolic acids,and promoted the germination rate.And the mixture of B1-2/B1-6 and B1-6/B2 enhanced the relieving effect of p-hydroxybenzoic acid on inhibiting peanut germination rate(RI>-0.25).In conclusion,the physical and chemical characteristics and the diversities of bacterial population and function were different and correlated well in the rhizosphere soils of tea plant.The pH and Al was the most significant physical and chemical factors.Proteobacteria and Acidobacteria were the dominant bacteria in rhizosphere soil of tea garden,while the abundance of Acidobacteria was higher in rhizosphere soil with low pH.Bacteria in soils with lower pH showed lower metabolic activity of the six carbon sources,especially carboxylic acid and phenolic acids.Therefore,acidification is one major factor leading to the difference of bacterial population in tea garden soil,and Al enrichment may be an important cause of soil acidification.These results might help to reveal the mechanism of soil acidification and continuous cropping barrier in tea plants,which needs further investigation.