Effect of low-density polyethylene microplastics on incidence of cotton Verticillium wilt and the structure and function of rhizosphere microbial community

Microplastics have become a global environmental concern, but the impact of microplastics on plant disease remains poorly understood. The primary objective of this study was to evaluate the effects of low-density polyethylene (LDPE) microplastics on cotton Verticillium wilt (CVW), as well as the structure and function of the soil microbial community. Metagenomic sequencing was performed to characterize the microbial community composition of the cotton rhizosphere. The experiment consisted of five treatments: a control group, and four LDPE groups with concentrations set at 0.1%, 0.5%, 1.0%, and 2.5%, respectively. The results demonstrated that high-dose LDPE treatments reduced the cotton emergence rate by 1.47–4.41% and plant biomass by 14.58–34.64%. These findings suggest that high-dose LDPE may exert pronounced phytotoxic effects on cotton plants. Although the populations of Verticillium dahliae did not differ significantly across treatments, LDPE microplastics at concentrations of 0.5–2.5% significantly exacerbated CVW, elevating the disease index by 54.29–71.67%. Statistical analysis revealed that LDPE microplastics altered the contents of soil nitrate nitrogen (NO 3 − -N) and available phosphorus (AP), with NO 3 − -N increasing by 16.86%-85.63% and AP by 51.16–69.77%. Meanwhile, LDPE microplastics triggered substantial alterations in the structure of rhizosphere microbial communities, as well as in their functional potential (assessed via KEGG pathway annotation). Microbial community structure and KEGG pathways were both significantly changed by soil nutrients (NO 3 − -N, NH 4 + -N, AP, AK). Moreover, partial least squares path modeling (PLS-PM) suggested that LDPE treatment indirectly influenced DI through two pathways: one was a positive effect mediated by alternations in fungal community structure and function, and the other was a negative effect driven by changes in soil nutrients. The exacerbation of CVW was closely linked to LDPE-induced dysbiosis in the cotton rhizosphere microenvironment.