Variation of soil microbiome in licorice rhizosphere driven with inoculating dark septate endophytes under drought stress

Abstract

BackgroundDark septate endophytes (DSE) are facultative biotrophic ascomycetes that colonize plant roots either alone or with arbuscular mycorrhizal (AM) fungi. DSE may provide nutrients to their plant hosts and help them adapt to various abiotic and biotic stresses. DSE inoculation under drought stress increased the biomass, root exudates, and AM fungi in the licorice (Glycyrrhiza uralensis Fisch.) rhizosphere. We conducted a pot experiment to establish whether the responses of licorice to DSE inoculation under drought stress are caused by changes in the rhizosphere microbiome. Each pot was inoculated with either Acrocalymma vagum or Paraboeremia putaminum. One set of pots was inoculated with a sterile culture medium. All three DSE-treated and uninoculated pots were subjected either to a well-watered (70% field water capacity, FWC) or drought stress (30% FWC) water regime. Rhizosphere microbiome compositions were measured by Illumina MiSeq sequencing of the 16S and ITS2 rRNA genes.ResultsIn total, 1,278 fungal and 1,583 bacterial operational taxonomic units (OUTs) were obtained at a 97% sequence similarity level. Ascomycota were the predominant fungi and Proteobacteria, Actinobacteria, Chloroflexi and Firmicutes were the predominant bacteria. DSE inoculation and water regime significantly influenced the rhizosphere microbiome composition. However, the effects of DSE on the fungal community were greater than those on the bacterial community. Paraboeremia putaminum exerted a stronger impact on the licorice rhizosphere microbiome than Acrocalymma vagum under drought stress. The observed changes in edaphic factors (water condition, soil organic matter, available N, available P, and available K) caused by DSE inoculation could be explained by the variations in rhizosphere microbiome composition. A network analysis indicated that DSE inoculation augmented the relative abundance of beneficial symbiotrophic fungi and growth-promoting bacteria but diminished the relative abundance of pathogens in the licorice rhizosphere.ConclusionsThe present study showed that the licorice rhizosphere microbial community differed between the DSE-inoculated and uninoculated plants. DSE had a stronger influence on the fungal than on the bacterial rhizosphere community under drought stress. These give us the guidance to develop biofertilizers with DSE consortia to enhance the cultivation of medicinal plants by shaping soil microbial community structure in dryland agriculture.