Abstract
Root-associated microbial communities are very important in the adaptation of halophytes to coastal environments. However, little has been reported on microbial community structures related to halophytes, or on comparisons of their compositions among halophytic plant species. Here, we studied the diversity and community structure of both rhizosphere and root endosphere bacteria in two halophytic plants: Glaux maritima and Salicornia europaea. We sampled the rhizosphere, the root endosphere, and bulk control soil samples, and performed bacterial 16S rRNA sequencing using the Illumina MiSeq platform to characterize the bacterial community diversities in the rhizosphere and root endosphere of both halophytes. Among the G. maritima samples, the richness and diversity of bacteria in the rhizosphere were higher than those in the root endosphere but were lower than those of the bulk soil. In contrast for S. europaea, the bulk soil, the rhizosphere, and the root endosphere all had similar bacterial richness and diversity. The number of unique operational taxonomic units within the root endosphere, the rhizosphere, and the bulk soil were 181, 366, and 924 in G. maritima and 126, 416, and 596 in S. europaea, respectively, implying habitat-specific patterns for each halophyte. In total, 35 phyla and 566 genera were identified. The dominant phyla across all samples were Proteobacteria and Bacteroidetes. Actinobacteria was extremely abundant in the root endosphere from G. maritima. Beneficial bacterial genera were enriched in the root endosphere and rhizosphere in both halophytes. Rhizobium, Actinoplanes, and Marinomonas were highly abundant in G. maritima, whereas Sulfurimonas and Coleofasciculus were highly abundant in S. europaea. A principal coordinate analysis demonstrated significant differences in the microbiota composition associated with the plant species and type of sample. These results strongly indicate that there are clear differences in bacterial community structure and diversity between G. maritima and S. europaea. This is the first report to characterize the root microbiome of G. maritima, and to compare the diversity and community structure of rhizosphere and root endosphere bacteria between G. maritima and S. europaea.
Highlights
Salinity affects more than 800 million hectares of the total agricultural land, leading to a decrease of approximately 1–2% of the global arid and semi-arid zones every year (Kouam and Marie Solange Mandou, 2017; Etesami and Beattie, 2018)
The highest richness was in the G. maritima bulk control soil (Bl) control soil sample, exhibiting significantly higher operational taxonomic units (OTUs) (P = 0.0011), Chao1 (P = 0.0011), and Shannon (P = 0.0006) indices compared with the G. maritima root endosphere (Re) samples
A comparison of alpha diversity metrics revealed a disparity in the OTU, Chao, and Shannon indices in the Rh samples from G. maritima compared with the Re samples (P = 0.0096, 0.0096, and 0.0081, respectively) (Figure 1 and Table 1)
Summary
Salinity affects more than 800 million hectares of the total agricultural land, leading to a decrease of approximately 1–2% of the global arid and semi-arid zones every year (Kouam and Marie Solange Mandou, 2017; Etesami and Beattie, 2018). Future agricultural production in salt-damaged fields, requires the development of salt-tolerant crops (Etesami and Beattie, 2018). To generate crops that are able to grow on salt-damaged fields, a large amount of basic research has focused on funding and characterizing salt-resistant-related genes in model plants, and using these to improve plant salt tolerance through genetic modification and editing. Despite numerous studies, only minor success has been achieved, as these approaches have often overlooked the important role of plant–microbe interactions in response to salt stress conditions (Coleman-Derr and Tringe, 2014; Yuan et al, 2016). It is wellknown that the plant-associated microbial community plays an important role in adapting plants to extreme environments (Redman et al, 2002; Yuan et al, 2016)
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