Paenibacillus polymyxa NSY50 suppresses Fusarium wilt in cucumbers by regulating the rhizospheric microbial community

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.

Bacterial Seed Endophytes of Domesticated Cucurbits Antagonize Fungal and Oomycete Pathogens Including Powdery Mildew

“…Similarly, 3 out of 4 isolates belonging to the genus Paenibacillus (and one isolate belonging to the genus Pantoea ) identified from wheat seeds of a commercial variety exhibited anti- F. graminearum activity in the dual culture assay ( Díaz Herrera et al, 2016 ). Moreover, a P. polymyxa strain isolated from the vinegar industry showed effective suppression of Fusarium wilt in cucumber and promoted other beneficial microbes to successfully compete against the causative agent ( F. oxysporum , a soil pathogen) for colonizing the rhizospheric niche of cucumber ( Shi et al, 2017 ). P. polymyxa PB71 identified from seeds of Styrian oil pumpkin demonstrated antagonism against fungal diseases caused by Didymella bryoniae under greenhouse condition as well as suppression of powdery mildew during field trials, and improved pumpkin yield ( Fürnkranz et al, 2012 ).…”

Streptomyces lydicus M01 Regulates Soil Microbial Community and Alleviates Foliar Disease Caused by Alternaria alternata on Cucumbers

“…The disease severity index was rated 0-4 (0 = healthy; 1 = less than 25% of leaves wilted; 2 = 25-50% of leaves wilted; 3 = 50-75% of leaves wilted; 4 = 75-100% of leaves wilted). The disease index was calculated using the formula: Disease index = [ (rating × number of plants rated)/(total number of plants × highest rating)] × 100 (Shi et al, 2017). Cucumber leaves were frozen using liquid nitrogen and stored at −20 • C for later determination of antioxidases activities.…”

Community Structures and Antifungal Activity of Root-Associated Endophytic Actinobacteria in Healthy and Diseased Cucumber Plants and Streptomyces sp. HAAG3-15 as a Promising Biocontrol Agent

“…Cucumber Fusarium wilt, induced by the pathogen Fusarium oxysporum f. sp. cucumerinum, is a typical soil-borne fungal disease and also one of the most important cucumber diseases in worldwide [6,7]. The disease could reducẽ 10% to 30% of cucumber production and cause quality degradation, which results in serious economic losses [8,9].…”