Responses of phyllosphere microbiota and plant health to application of two different biocontrol agents

Chong Qin,Yabing Gu,Tianming Li,Tianbo Liu,Huaqun Yin,Yongjun Liu,Nengwen Xiao,Jiemeng Tao,Delong Meng

doi:10.1186/s13568-019-0765-x

Abstract

The phyllosphere supports a tremendous diversity of microbes, which have the potential to influence plant biogeography and ecosystem function. Although biocontrol agents (BCAs) have been used extensively for controlling plant diseases, the ecological effects of BCAs on phyllosphere bacteria and the relationships between phyllosphere community and plant health are poorly understood. In this study, we explored the control efficiency of two BCA communities on bacterial wildfire disease by repeatedly spraying BCAs on tobacco leaves. The results of field tests showed that BCAs used in our study, especially BCA_B, had remarkable control effects against tobacco wildfire disease. The higher control efficiency of BCA_B might be attributed to a highly diverse and complex community in the phyllosphere. By 16S ribosomal RNA gene sequencing, we found that phyllosphere microbial community, including community diversity, taxonomic composition and microbial interactions, changed significantly by application of BCAs. According to the correlation analysis, it showed that wildfire disease infection of plants was negatively related to phyllosphere microbial diversity, indicating a highly diverse community in the phyllosphere might prevent pathogens invasion and colonization. In addition, we inferred that a more complex network in the phyllosphere might be beneficial for decreasing the chances of bacterial wildfire outbreak, and the genera of Pantoea and Sphingomonas might play important roles in wildfire disease suppression. These correlations between phyllosphere community and plant health will improve our understanding on the ecological function of phyllosphere community on plants.

Highlights

Bacterial pathogens are associated with plant diseases and can account for major economic losses to agricultural production
2574 operational taxonomic unit (OTU) were clustered with 97% identity and 480 genera and 38 phyla were identified from this data when blast the sequences in RDP database (Additional file 1: Fig. S4)
The phyllosphere microbial community was dominated by the phylum Proteobacteria that averagely account for 88% of the microbial community, while at the genus level, Pseudomonas, Sphingomonas, Pantoea, Streptophyta, Tatumella, and Acinetobacter were the abundant genera that had an average relative abundance of more than 1%

Summary

Introduction

Bacterial pathogens are associated with plant diseases and can account for major economic losses to agricultural production. Several strategies have been recommended to control disease incidence and severity, such as chemical pesticides and biological control (Erwin and Ribeiro 1996). As an ecologically viable alternative, biological control has been a desirable strategy for controlling plant diseases (You et al 2015) and there are an increasing number of biocontrol agents (BCAs), such as Bacillus spp., Pseudomonas spp., Trichoderma spp. etc., being commercialized for various crops (Trabelsi and Mhamdi 2013; Cha et al 2016). Disease suppression by BCAs is the manifestation of interactions among the plant, the pathogen, the biocontrol agents, the microbial community on and around the plant, and the physical environment (Akhtar and Siddiqui 2010).

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