Browsing by Person "Liu, Yuan"

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Interactions of nitrogen-related, growth promoting bacteria with Miscanthus × giganteus : impact and mechanism
(2020) Liu, Yuan; Ludewig, Uwe
The highly nitrogen-use efficient biomass grass Miscanthus is a host of the bacterial endophyte Herbaspirillum frisingense. While Herbaspirillum frisingense has the genetic competence to fix nitrogen, the plant-associated microbiome may also contribute to this nitrogen efficiency. Furthermore, the costly field establishment of the sterile perennial Miscanthus × giganteus from rhizomes is a severe constraint for expanding the production area of this commercial biomass crop. In this study, the effect of Herbaspirillum frisingense inoculation on stem-cutting sprouting, shoot biomass and other yield parameters was investigated. I studied how the inoculation impacts on the M. × giganteus associated microbiome and how the long term differences in nitrogen fertilizer amount modulated the M. × giganteus associated microbiome. This was studied in a 14 year-old field trial of M. ×giganteus fertilized with various amounts of nitrogen. Stem cutting inoculation improved the shoot sprouting and establishment success of Miscanthus × giganteus in the greenhouse. In a small field trial, plant height and biomass from inoculated sites were significantly larger in the second year after establishment, but already after one year after inoculation, the bulk soil, rhizosphere, root and rhizome microbiomes were almost devoid of Herbaspirillum. This beta-proteobacterium may colonize the shoot of Miscanthus × giganteus more efficiently. Major differences between bacterial communities were determined by plant-soil compartments and less by the plant organs, while both inoculation and nitrogen had little effects on these communities. Compared to the little effect on the soil, rhizosphere and root microbiomes, the rhizome microbiome was massively modulated by both inoculation and nitrogen level. In the rhizome, several proteobacteria, which are associated with plant growth promoting functions, were enriched by inoculation, while N2-fixing-related bacterial families were favored by long-term nitrogen-deficiency plots, but denitrifier-related families were depleted. The studies suggest that H. frisingense inoculation may improve establishment of Miscanthus stem cuttings and has long-lasting effects on the rhizome microbiome diversity, despite low rhizocompetence and low root abundance. Meanwhile, the rhizome could be a potential nitrogen fixation factory. The organ-specific, nitrogen-related bacterial communities are modulated by long-term different nitrogen supply and are mainly shaped by the plant, which provides guidance for optimizing Miscanthus sustainable cultivation.