Response Characteristics of Bacterial Diversity and Enzyme Activity in Continuous Cropping Soil of Pitaya(Hylocereus undatus)to Phenolic Acid Metabolites
As the planting years of pitaya(Hylocereus undatus)increase,phenolic acid metabolites gradually accumulate in the soil,promoting the colonization of pathogenic bacteria,fungi,and nematodes,eventually causing continuous cropping obstacles.In this study,culturable bacteria were isolated from the rhizosphere soil of pitaya continuously cultivated for 6 years and 3 years using pure culture technique,and species identification was conducted through 16S rRNA gene sequencing.At the same time,soil enzyme activity assays were conducted to investigate changes in enzyme activity in pitaya soil over different planting durations,high performance liquid chromatography(HPLC)was utilized to identify and quantify the types and contents of phenolic acid metabolites in the soil,and the response characteristics of soil bacteria and enzyme activity to phenolic acid metabolites were analyzed.The results indicated that continuous cropping increased the diversity of bacterial communities in pitaya soil,a total of 112 strains,including 4 phyla,5 classes,10 orders,16 families,21 genera,56 species,were isolated from the rhizosphere soil,among which the relative abundance of biocontrol bacteria such as Pseudomonas,Burkholderia,and Bacillus decreased by 23.36％.In continuous cropping pitaya soil,catalase and cellulase activities decreased,whereas urease and sucrase activities increased,and the levels of gallic acid,ferulic acid,salicylic acid,and benzoic acid increased by 163.80％,194.92％,341.57％and 175.93％,respectively.Response relationship analysis showed that there was a certain correlation between phenolic acids and microbial community structure.The above results demonstrated that continuous cropping led to the accumulation of phenolic acids,including gallic acid,ferulic acid,salicylic acid,and benzoic acid,then caused an imbalance in the soil microbial community structure,a reduction in beneficial microorganisms,changes in soil enzyme activity,impaired nutrient absorption by plants,and ultimately resulted in continuous cropping obstacles.This study provides basic data for the subsequent development of microbial agents with phenolic acid degradation function and field management techniques for pitaya.
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