Screening, Identification and Efficacy Evaluation of Antagonistic Bacteria for Biocontrol of Soft Rot Disease Caused by Dickeya zeae

Jianuan Zhou,Lianhui Zhang,Guangtao Lu,Yang Xue,Jieling Li,Xia Chen,Ming Hu

doi:10.3390/microorganisms8050697

Jianuan Zhou, Lianhui Zhang + Show 5 more

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https://doi.org/10.3390/microorganisms8050697

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Abstract

Dickeya zeae is the causal agent of bacterial soft rot disease, with a wide range of hosts all over the world. At present, chemical agents, especially agricultural antibiotics, are commonly used in the prevention and control of bacterial soft rot, causing the emergence of resistant pathogens and therefore increasing the difficulty of disease prevention and control. This study aims to provide a safer and more effective biocontrol method for soft rot disease caused by D. zeae. The spot-on-lawn assay was used to screen antagonistic bacteria, and three strains including SC3, SC11 and 3-10 revealed strong antagonistic effects and were identified as Pseudomonas fluorescens, P. parafulva and Bacillus velezensis, respectively, using multi-locus sequence analysis (MLSA) based on the sequences of 16S rRNA and other housekeeping genes. In vitro antimicrobial activity showed that two Pseudomonas strains SC3 and SC11 were only antagonistic to some pathogenic bacteria, while strain 3-10 had broad-spectrum antimicrobial activity on both pathogenic bacteria and fungi. Evaluation of control efficacy in greenhouse trials showed that they all restrained the occurrence and development of soft rot disease caused by D. zeae MS2 or EC1. Among them, strain SC3 had the most impressive biocontrol efficacy on alleviating the soft rot symptoms on both monocotyledonous and dicotyledonous hosts, and strain 3-10 additionally reduced the occurrence of banana wilt disease caused by Fusarium oxysporum f. sp. cubensis. This is the first report of P. fluorescens, P. parafulva and B. velezensis as potential bio-reagents on controlling soft rot disease caused by D. zeae.

Highlights

Dickeya zeae, formerly named Erwinia chrysanthemi pv. zeae, is the causal agent responsible for maize stalk rot, rice foot rot and banana soft rot diseases in different parts of the world [1,2,3,4,5]
The findings in this study provide Pseudomonas fluorescens SC3, P. parafulva SC11 and Bacillus velezensis 3–10 as Dickeya novel biocontrol agents for potential application on bacterial disease control
Based on the effective inhibitory activity of strain 3-10 on fungal pathogen, we tested its efficacy on controlling banana wilt disease caused by F. oxysporum f. sp. cubensis FOC4, since we found that banana wilt disease and soft rot disease often occurred at the same time in the field according to our investigations

Summary

Introduction

Formerly named Erwinia chrysanthemi pv. zeae, is the causal agent responsible for maize stalk rot, rice foot rot and banana soft rot diseases in different parts of the world [1,2,3,4,5]. Zeae, is the causal agent responsible for maize stalk rot, rice foot rot and banana soft rot diseases in different parts of the world [1,2,3,4,5] It has been found in Asia, America, Australia, Europe and Africa, threatening agricultural production [6]. Rice foot rot mainly occurs in south China, with yield loss ranging from 10% to 30%, and even over 60% in some rice planting regions in China [10,11,12,13,14] It threatened different rice-cultivated areas in many Southeast Asian countries and Europe [6,15]. The pathogen is able to spread via water, survive on field weeds and plant debris, increasing the difficulty of prevention and control of soft rot disease [1]

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