Isolation of Burkholderia sp. HQB-1, A Promising Biocontrol Bacteria to Protect Banana Against Fusarium Wilt Through Phenazine-1-Carboxylic Acid Secretion.

Zhizhou Xu,Jianfu Liu,Jinpeng Du,Yinglong Chen,Mingyuan Wang,Tao Dong,Ting Huang

doi:10.3389/fmicb.2020.605152

Abstract

Fusarium wilt is a devastating soil-borne fungal disease caused by Fusarium oxysporum f.sp. cubense (Foc). In recent years, some antifungal bacteria have been applied for the prevention and biocontrol of pathogenic fungi. In our study, a bacterial strain HQB-1, isolated from banana rhizosphere soil, was cultured for investigation. It showed broad-spectrum antifungal activities against representative phytopathogenic fungi including Fusarium oxysporum, Colletotrichum gloeosporioides, Botrytis cinerea, and Curvularia fallax. The strain HQB-1 was identified as Burkholderia sp. by morphological, physiological, and biochemical examinations, confirmed by 16S rRNA gene sequence analysis. Among the metabolites produced by the strain, we identified an antifungal compound which was identified phenazine-1-carboxylic acid (PCA) (C13H8N2O2) through ultraviolet, liquid chromatography quadrupole-time of flight mass spectrometer, and nuclear magnetic response. Furthermore, PCA exhibited the lowest minimum inhibitory concentration (MIC) against F. oxysporum (1.56 μg/ml) and yielded the highest MIC against C. gloeosporioides. Pot experiments showed that application of 5 μg/ml or more of PCA efficiently controlled banana wilt and promoted the growth of banana plants. These results suggested that Burkholderia sp. HQB-1, as an important microbial resource of PCA, could be a promising biological agent against wilt diseases and promoting banana growth.

Highlights

Banana (Musa spp.), is one of the most important fruit crops, widely cultivated in tropical and subtropical areas, providing staple food for over 400 million people (Dale et al, 2017)
The screening of antagonistic bacteria from soil microorganisms in fields with banana Fusarium wilt is of great practical significance in controlling this disease (Duan et al, 2020)
In the soil bacteria community of healthy banana plants, the Burkholderia may be one of the most abundant genera that contribute to suppressing Fusarium wilt (Shen et al, 2014)

Summary

Introduction

Banana (Musa spp.), is one of the most important fruit crops, widely cultivated in tropical and subtropical areas, providing staple food for over 400 million people (Dale et al, 2017). In recent years, Fusarium wilt, known as Panama disease, has Biocontrol Burkholderia and Antifungal Metabolites become one of the most destructive soil-borne diseases threatening banana production worldwide (Davis et al, 1996; Ploetz, 2005; Fourie et al, 2011). It has been demonstrated that the pathogen Foc TR4 can infect banana roots, penetrate into the root xylem, spread into the rhizome and pseudostem xylem within several days after infection (Warman and Aitken, 2018), and eventually cause the occlusion of vascular bundle and the blocking of water and nutrients transportation (Li et al, 2017). Because the chlamydospores of Foc TR4 can survive for a long period of time in soil (Viljoen, 2002), it is becoming one of the most crucial limiting factors in banana production (O’Donnell et al, 1998; Lin et al, 2009). It is necessary and imperative to efficiently control the occurrence and spread of Foc TR4 in banana

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