The influence of different concentrations of bio-organic fertilizer on cucumber Fusarium wilt and soil microflora alterations

Nan Huang,Weiping Wang,Xiaojuan Chang,Yanlai Yao,Weiwei Wang,Fengxiang Zhu,Sabrina Sarrocco

doi:10.1371/journal.pone.0171490

Abstract

Fusarium wilt is one of the main diseases of cucumber, and bio-organic fertilizer has been used to control Fusarium wilt. In this study, a pot experiment was conducted to evaluate the effects of bio-organic fertilizer applied at four levels on the suppression of Fusarium wilt disease in cucumber, the soil physico-chemical properties and the microbial communities. In comparison with the control (CK), low concentrations of bio-organic fertilizer (BIO2.5 and BIO5) did not effectively reduce the disease incidence and had little effect on soil microorganisms. High concentrations of bio-organic fertilizer (BIO10 and BIO20) significantly reduced the disease incidence by 33.3%-66.7% and the production was significantly improved by 83.8%-100.3%. The soil population of F. oxysporum f. sp. cucumerinum was significantly lower in bio-organic fertilizer treatments, especially in BIO10 and BIO20. The microorganism activity increased with the bio-organic fertilizer concentration. High-throughput sequencing demonstrated that, at the order level, Sphingomonadales, Bacillales, Solibacterales and Xylariales were significantly abundant in BIO10 and BIO20 soils. At the genus level, the abundance and composition of bacterial and fungal communities in BIO10 and BIO20 were similar, illustrating that high concentrations of bio-organic fertilizer activated diverse groups of microorganisms. Redundancy analysis (RDA) showed that Xanthomonadales, Sphingomonadales, Bacillales, Orbiliales, Sordariales, and Mucorales occurred predominantly in the BIO10 and BIO20. These microorganisms were related to the organic matter, available potassium and available phosphorus contents. In conclusion, a high concentration of bio-organic fertilizer application suppressed the Fusarium wilt disease and increased cucumber production after continuous cropping might through improving soil chemical condition and manipulating the composition of soil microbial community.

Highlights

Fusarium wilt of cucumber is a common soilborne disease observed all over the world that is caused by Fusarium oxysporum f. sp. cucumerinum, a typical soil-born pathogen
Chemical fungicides might lead to environment pollution, have toxic effects on human health, and create imbalances in the microbial community [1], and the effectiveness of crop rotation is limited once a disease outbreak occurs [2]
Soil inoculation of plant growth-promoting rhizobacteria (PGPR) without a suitable organic substrate will not result in stable biological control against soil-born pathogens because inoculated antagonists compete for nutrients with other native soil microbes to survive

Summary

Introduction

Fusarium wilt of cucumber is a common soilborne disease observed all over the world that is caused by Fusarium oxysporum f. sp. cucumerinum, a typical soil-born pathogen. Crop rotation and soil fumigation are usually used to control Fusarium wilt. Chemical fungicides might lead to environment pollution, have toxic effects on human health, and create imbalances in the microbial community [1], and the effectiveness of crop rotation is limited once a disease outbreak occurs [2]. Biological control represents a potentially attractive alternative disease management approach and may eventually replace some overused chemical pesticides in agriculture [4]. Compost can stimulate the proliferation of antagonists in the soil and suppress soil-borne pathogens. Soil inoculation of PGPR without a suitable organic substrate will not result in stable biological control against soil-born pathogens because inoculated antagonists compete for nutrients with other native soil microbes to survive.

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