Abstract
This study examined the relationship between host plant and rhizospheric bacterial community structure, including composition and diversity, in Triticum and Aegilops species (12 and two accessions, respectively) as well as three closely related species, barley, rye and oat (four accessions), to explore the possibility that wheat root and rhizosphere interaction can be utilized for wheat breeding and biotechnology in the future. For this purpose, DNA was isolated from rhizospheric soil samples and one control non-rhizospheric soil sample, and the 16S rRNA gene region was amplified and subjected to DNA pyrosequencing. A total of 132,888 amplicons were analyzed. Bacterial composition at the phylum level was similar among the 18 rhizospheric samples; however, the proportion of Acidobacteria was much lower in these samples than in the control non-rhizospheric soil sample, indicating that rhizospheres influenced the bacterial composition even at the higher taxonomic level. Across host plant genome types (three levels of ploidy and three major genomes, A, B and D), there was no detectable difference in phylum composition or species diversity. Estimated bacterial species diversity was higher in the control soil sample than in plant rhizospheric soils, implying that bacterial species diversity was reduced in rhizospheres. A PCoA plot and UPGMA dendrogram based on the bacterial species composition showed that control soil was distantly located from the plant rhizospheric samples and that Triticum, Aegilops and related species were well separated. PERMANOVA analysis detected statistically significant differentiation among these four groups. Clustering of Triticum species suggested that the A genome was dominant over the B and D genomes, with respect to the influence on rhizospheric bacterial species composition. Although the cause was not investigated in this study, these results clearly indicated that the genetic constitution of the plant host exerted a strong influence on rhizospheric bacterial community structure.
Highlights
The rhizosphere is an interface between plant roots, the soil and the soil microbiome, in which all organisms interact (Peiffer et al, 2013)
The results showed that bacterial composition was drastically different in rhizospheric samples from that in control soil, and that the differences could relate to adherence of bacteria to plant roots, plant age, field site and planting sequence
Bacterial composition at the phylum level The phylum composition in rhizospheric bacterial communities was similar among 18 plant species and control soil (Fig. 1)
Summary
The rhizosphere is an interface between plant roots, the soil and the soil microbiome, in which all organisms interact (Peiffer et al, 2013). Many microorganisms associated with plant roots provide the host plant with critical (Hinsinger et al, 2006) These functions of host plants can directly affect the composition and diversity of rhizospheric microbial communities. It was reported that the microbial community structure varies significantly in rhizospheric soil associated with different plant species (Wieland et al, 2001; Kuske et al, 2002) or plant genotypes (Aira et al, 2010). This study identified differences in the microbial communities associated with maize genotype variants of the su and sh genes, which influence carbon storage (Aira et al, 2010) These results indicated that different plant species and genotypes of plant species could influence the structure (diversity and composition) of the root-associated microbial community. It was suggested that it would be valuable to understand these interactions between plants and microorganisms in root and to identify the plant alleles related to these interactions for future plant breeding and biotechnology (Peiffer et al, 2013)
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