Reclaimed water is considered to be a reasonable and sustainable alternative water resource to improve water resource layout and mitigate the shortage of traditional water resources. Its use in irrigation will cause changes in the microbial community structure and opportunistic pathogen abundance in soils and crops, but few studies have been conducted on this subject. Peppers were used as the research subjects, and the treatments were direct irrigation of reclaimed water, mixed irrigation with freshwater and reclaimed water, rotated irrigation with freshwater and reclaimed water, with potable water irrigation as the control. The effects of different irrigation methods of reclaimed water on the soil physicochemical properties were analyzed through a pot experiment. Furthermore, changes in bacterial community and opportunistic pathogen abundance in pepper fruit and the rhizosphere under reclaimed water irrigation conditions were investigated based on high-throughput sequencing technology and quantitative PCR methods. The results showed that direct irrigation with reclaimed water increased soil EC and decreased soil pH. 16S rDNA high-throughput sequencing showed that Proteobacteria, Bacteroides, Actinobacteria, and Firmicutes were present in both pepper fruit and the rhizosphere at phylum level, and the most dominant genera (Pantoea, Pseudomonas, Sphingomonas, Sphingopyxis, Luteimonas, and Mariniflexile) were greatly affected by reclaimed water irrigation methods. Quantitative PCR results indicated that the influence of reclaimed water irrigation on the distribution and abundance of pathogenic bacteria in the soil-pepper system was different, and the abundance of Legionella spp. in pepper fruit and Pseudomonas syringae in the rhizosphere increased with reclaimed water irrigation. Our results indicated that the reclaimed water was suitable for agricultural irrigation, but different reclaimed water irrigation methods may introduce different degrees of microbial contamination. In addition, attention must be given to some opportunistic pathogens and phytopathogens.
Keywords: bacterial diversity; high-throughput sequencing; pathogens; real-time quantitative PCR; reclaimed water irrigation.