Novel soil fumigation method for suppressing cucumber Fusarium wilt disease associated with soil microflora alterations

Abstract

Fusarium wilt in cucumber results from continuous cropping and is a serious soil-borne fungal disease that threatens cucumber production around the world. The application of a novel fumigation agent based on ammonium bicarbonate to the soil as a strategy for controlling Fusarium wilt and its effects on soil microflora was investigated in a field with serious disease incidence in this study. Overall, the results showed that fumigation effectively controlled cucumber Fusarium wilt disease and significantly increased the total and mean cucumber fruit weight. Real-Time PCR results showed that the total bacterial and fungal numbers in the treatment (LAB) significantly decreased after fumigation and that significantly fewer fungi were observed after harvest (LABOF). The next-generation sequencing of the 16S rRNA and internal transcribed spacer (ITS) genes using MiSeq platform showed that the soil bacterial and fungal community structures in the fumigation treatment were significantly different from the control without fumigation regardless after fumigation or harvest. Compared to the control, higher abundances of Gemmatimonadetes, Verrucomicrobia and Zygomycota, and lower abundance of Ascomycota were observed in the fumigated soils after fumigation and harvest. Furthermore, the abundances of Mortierella and Gp1 were significantly higher. Most importantly, the abundance of Fusarium, which includes the pathogen potentially responsible for cucumber Fusarium wilt disease, was significantly lower in the fumigated soils after harvest. Redundancy analysis showed that the fumigated soils were dominated by Ohtaekwangia, Gp6, and Gp4, which were related to the soil total nitrogen (TN), ammonium nitrogen (NH4–N) and nitrate nitrogen (NO3–N) contents. In addition, Penicillium and Pseudaleuria fungi were dominant in the treatment and control, and the control was dominated by Fusarium. In conclusion, the observed disease suppression due to the novel ecological soil fumigation strategy may be attributed to general suppression resulting from altered soil properties, such as higher soil NH4–N, NO3–N and TON contents, and the alteration of the disturbed soil microflora in a cucumber monoculture system.