Date Published: March 28, 2019
Publisher: Springer Berlin Heidelberg
Author(s): Chong Qin, Jiemeng Tao, Tianbo Liu, Yongjun Liu, Nengwen Xiao, Tianming Li, Yabing Gu, Huaqun Yin, Delong Meng.
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.
Bacterial pathogens are associated with plant diseases and can account for major economic losses to agricultural production. The management of plant diseases in the sustainable agriculture has become a challenge for plant pathologist. Several strategies have been recommended to control disease incidence and severity, such as chemical pesticides and biological control (Erwin and Ribeiro 1996). However, the use of chemical pesticides often results in environmental and food quality problems (Sharma et al. 2012). 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).
The relationship between the bacterial community and crop morbidity is an important topic in microbial ecology and biocontrol of crop disease (Xiao et al. 2018). Previous studies in biological control have mainly focused on soil bacterial community and revealed that soil bacterial community played a critical role in crop disease incidence (Wang et al. 2017; Yang et al. 2017). However, very few investigations have been conducted to address the potential interactions between introduced BCAs, indigenous microbial communities in the phyllosphere and crop health. As many foliar bacterial pathogens colonize plant surfaces before infection, the microbiology of the phyllosphere has been applied to the promotion of plant growth and plant protection recently (Vorholt 2012). Tobacco wildfire disease caused by Pseudomonas syringae pv. tabaci is the main leaf bacterial disease on tobacco. In this study, we investigated the responses of phyllosphere microbiota and plant health to application of two BCAs. The results showed that application of BCAs, especially BCA_B, could decrease the plant disease infection rate and disease index significantly. Phyllosphere bacterial community, including bacterial composition, taxonomic and phylogenetic diversity, community structure, and microbial interactions, showed great changes by application of BCAs. Through further analyses, it was found that community diversity of the phyllosphere was negatively correlated to disease infection rate and the disease index.