Abstract

Paenibacillus polymyxa (P. polymyxa) NSY50, isolated from vinegar residue substrate, suppresses the growth of Fusarium oxysporum in the cucumber rhizosphere and protects the host plant from pathogen invasion. The aim of the present study was to evaluate the effects of NSY50 application on cucumber growth, soil properties and composition of the rhizospheric soil microbial community after exposure to Fusarium oxysporum. Bacterial and fungal communities were investigated by Illumina sequencing of the 16S rRNA gene and the internal transcribed spacer (ITS) regions (ITS1 and ITS2). The results showed that NSY50 effectively reduced the incidence of Fusarium wilt (56.4%) by altering the soil physico-chemical properties (e.g., pH, Cmic, Rmic, total N and Corg) and enzyme activities, especially of urease and β-glucosidase, which were significantly increased by 2.25- and 2.64-fold, respectively, relative to the pathogen treatment condition. More specifically, NSY50 application reduced the abundance of Fusarium and promoted potentially beneficial groups, including the Bacillus, Actinobacteria, Streptomyces, Actinospica, Catenulispora and Pseudomonas genera. Thus, our results suggest that NSY50 application can improve soil properties, shift the microbial community by increasing beneficial strains and decreasing pathogen colonization in the cucumber rhizosphere, and reduce the occurrence of cucumber Fusarium wilt, thereby promoting cucumber growth.

Highlights

  • To successfully suppress various diseases[20,21,22]

  • The growth indices of cucumbers grown with NSY50 +FOC increased significantly in comparison with those grown with FOC alone

  • The rhizosphere microbiome in different conditions varies in diversity and in the response to soil environmental changes; they are essential for controlling plant diseases and, plant health

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Summary

Introduction

To successfully suppress various diseases[20,21,22]. In turn, the soil enzymatic activities, plant species, and soil type influence the composition of the microbial community, contributing to plant disease suppression[23,24,25,26]. The 16S rRNA gene and the internal transcribed spacer (ITS) region are widely used to analyse soil bacterial and fungal communities[30,31,32,33], respectively. This approach has provided insights into ecological processes and the soil microbial community. The objectives of this study were (1) to evaluate the effects of NSY50 on the suppression of FOC in cucumbers, (2) to compare the differences in the composition of the rhizospheric microbial community after challenge with NSY50 and FOC using Illumina sequencing technology, and (3) to further illustrate the mechanisms of soil-borne disease suppression

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