A Newly Isolated Streptomyces sp. YYS-7 With a Broad-Spectrum Antifungal Activity Improves the Banana Plant Resistance to Fusarium oxysporum f. sp. cubense Tropical Race 4.

Yuanyuan Wei,Wen Tang,Yufeng Chen,Dengfeng Qi,Yankun Zhao,Kai Li,Jianghui Xie,Dengbo Zhou,Wei Wang,Xiaoping Zang,Tao Jing

doi:10.3389/fmicb.2020.01712

Yuanyuan Wei, Wen Tang + Show 9 more

Open Access

https://doi.org/10.3389/fmicb.2020.01712

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Abstract

Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense (Foc) is one of the most destructive diseases, severely limiting the development of banana industry. Especially, Foc tropical race 4 (Foc TR4) can infect and destroy almost all banana cultivars. Until now, there is still a lack of an effective method for controlling fusarium wilt. A biocontrol strategy using Actinobacteria is considered as a promising method for management of disease and pest. In this study, 229 Actinobacteria were isolated from rhizosphere soil samples of a primitive ecological mountain. An actinobacterium strain marked with YYS-7 exhibited a high antifungal activity against Foc TR4. Combining the physiological and biochemical characteristics as well as alignment of the 16S rRNA sequence, the strain YYS-7 was assigned to Streptomyces sp. The crude extracts of Streptomyces sp. YYS-7 obviously inhibited the mycelial growth of Foc TR4. The cell integrity and ultrastructure were seriously destroyed. In addition, Streptomyces sp. YYS-7 and crude extracts also showed a broad-spectrum antifungal activity against the selected seven phytopathogenic fungi. A gas chromatography-mass spectrometry (GC-MS) was used to predict the antifungal metabolites. A total of eleven different compounds were identified, including phenolic compounds, hydrocarbons, esters and acids. In the pot experiment, the crude extracts can significantly improve the banana plant’s resistance to Foc TR4. Hence, Streptomyces sp. YYS-7 will be a potential biocontrol agent for the biofertilizer exploitation and the discovery of new bioactive substances.

Highlights

Plant diseases caused by various phytopathogens seriously result in the global crop yield reduction
An isolate numbered with YYS-7 had the strongest antifungal activity
The strain YYS-7 with a strong antifungal activity against Foc tropical race 4 (Foc TR4) was isolated from the rhizosphere soil samples of plants in the primitive mountain

Summary

Introduction

Plant diseases caused by various phytopathogens seriously result in the global crop yield reduction. Safe and effective biocontrol methods have received more attention for management of various fungal diseases (Raza et al, 2016; Zapata-Sarmientoa et al, 2019) Different microbial species such as bacteria, fungi and Actinobacteria have been successfully used for controlling plant pathogens (Supaphon et al, 2013; Raza et al, 2016; Soltanzadeh et al, 2016; Zapata-Sarmientoa et al, 2019). Various secondary metabolites with novel structure and remarkable biological activities were identified and successfully developed into formulations to control fungal phytopathogens of various crops (Ayyadurai et al, 2006; Faheem et al, 2015; Goudjal et al, 2016; Lu et al, 2016; Duan et al, 2020) Selection of these functional microbes is limited by their growth conditions and antifungal activities. It is important to isolate effective antagonistic Streptomyces against different phytopathogenic fungi

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