| Chlorpyrifos (C9H11Cl3NO3PS) is a broad-spectrum chlorinated organophosphate insecticide, nematicide and acaricide used for pest control on various crops (cotton, rice, etc.), as well as lawns and ornamental plants. Rhizosphere soil microbial communities play an important role in mineral nutrients, pathogen control, soil nutrient cycling and plant growth. Chlorpyrifos repeatedly applied would threaten the rhizosphere soil microbial community structure, function, sustainable development of agriculture and human health. Currently, the effect of chlorpyrifos on cotton rhizosphere soil microbial community structure, function and cotton growth has not yet been reported. Thus, to investigate and estimate the effect of chlorpyrifos on cotton rhizosphere soil microbial community structure, function and its growth are important.In this study, to investigate effects of 5 mg·kg-1 (recommended dose),10 mg·kg-1,15 mg·kg-1 and 20 mg·kg-1 concentration of chlorpyrifos on cotton growth, rhizosphere soil microbial community structure and function, the equipments, such as, light incubator, high performance liquid chromatography (HPLC), terminal restriction fragment length polymorphism (T-RFLP), Illumina MiSeq platform and Illumina NextSeq 500 platform sequencing technology were used.Results showed that the degradation half-lives of chlorpyrifos at levels of 5 mg·kg-1,10 mg·kg-1,15 mg·kg-1 and 20 mg·kg-1 in soil were calculated to be 10.04 d,11.36 d,11.55 d and 12.16 d, respectively.97% of applied chlorpyrifos were degraded within 60 d. The higher concentration of applied chlorpyrifos was, the longer degradation half-live of chlorpyrifos was. Cotton growth of chlorpyrifos treatments were significantly weaker than those of control. The higher concentration of applied chlorpyrifos was, the weaker cotton growth was.For cotton rhizosphere soil, we chose terminal restriction fragment length polymorphism (T-RFLP) analysis technology to investigate the effect of chlorpyrifos on rhizosphere soil bacterial community. The results showed that the cotton rhizosphere soil bacterial community diversities were significantly inhibited during 30 d and basically recovered to the normal level after 60 d in 5-20 mg·kg-1 concentration of chlorpyrifos treatments. The higher concentration of chlorpyrifos was, the longer recovery time of bacterial community diversity was. The bacterial community structure was significantly different between chlorpyrifos treatment and control. The higher concentration of chlorpyrifos was, the more apparent different of bacterial community structure was. The taxonomic interpretation of TRFs revealed that the relative abundances of part bacteria were significantly changed.For Illumina Miseq platform sequencing, results showed that cotton rhizosphere soil bacterial community diversity was significantly inhibited after 30 d in 15 mg·kg-1 concentration of chlorpyrifos treatment. The bacterial community structure was significantly changed, too. Dominant bacteria in cotton rhizosphere soil were Proteobacteria, Acidobacteria, Bacteroidetes, Actinobacteria, Gemmatimonadetes and Chloroflexi and so on. After chlorpyrifos treatment, Streptomyces, Paracoccus, Flavihumibacter, Klebsiella, Bacillus cereus and Pseudomonas stutzeri were induced, which could degrade chlorpyrifos. Methylibium, Azoarcus and Nitrospira were inhibited.For Illumina NextSeq 500 platform sequencing, results showed that cotton rhizosphere soil fungal community was affected after 30 d in 15 mg·kg-1 concentration of chlorpyrifos treatment. Those genes involved in nocardicin A, streptomycin, nitrite reductase (NADH) small subunit, nitrous-oxide reductase, ferredoxin-nitrate reductase, Fe3+ transport system protein and nitrogen regulation response regulator GlnG biosynthesises were significantly inhibited. Applied chlorpyrifos significantly changed soil microbial functions such as nitrogen cycle, antibiotic biosynthesis, iron regulator and so on.This study systematically evaluated the effect of chlorpyrifos on cotton rhizosphere soil microbial community and function. Applied chlorpyrifos have a significantly impact on the cotton rhizosphere soil microbial community and function. Chlorpyrifos may have a direct or (and) indirect inhibition on cotton growth. It provides important information for using chlorpyrifos efficient and safety. Chlorpyrifos has adverse effect on cotton rhizosphere soil micro-ecology. We should give attention to the ecological security of chlorpyrifos. |
