A simplified synthetic community rescues Astragalus mongholicus from root rot disease by activating plant-induced systemic resistance

Abstract

Background Plant health and growth are negatively affected by pathogen invasion; however, plants can dynamically modulate their rhizosphere microbiome and adapt to such biotic stresses. Although plant-recruited protective microbes can be assembled into synthetic communities for application in the control of plant disease, rhizosphere microbial communities commonly contain some taxa at low abundance. The roles of low-abundance microbes in synthetic communities remain unclear; it is also unclear whether all the microbes enriched by plants can enhance host adaptation to the environment. Here, we assembled a synthetic community with a disease resistance function based on differential analysis of root-associated bacterial community composition. We further simplified the synthetic community and investigated the roles of low-abundance bacteria in the control of Astragalus mongholicus root rot disease by a simple synthetic community. Results Fusarium oxysporum infection reduced bacterial Shannon diversity and significantly affected the bacterial community composition in the rhizosphere and roots of Astragalus mongholicus. Under fungal pathogen challenge, Astragalus mongholicus recruited some beneficial bacteria such as Stenotrophomonas, Achromobacter, Pseudomonas, and Flavobacterium to the rhizosphere and roots. We constructed a disease-resistant bacterial community containing 10 high- and three low-abundance bacteria enriched in diseased roots. After the joint selection of plants and pathogens, the complex synthetic community was further simplified into a four-species community composed of three high-abundance bacteria (Stenotrophomonas sp., Rhizobium sp., Ochrobactrum sp.) and one low-abundance bacterium (Advenella sp.). Notably, a simple community containing these four strains and a thirteen-species community had similar effects on the control root rot disease. Furthermore, the simple community protected plants via a synergistic effect of highly abundant bacteria inhibiting fungal pathogen growth and less abundant bacteria activating plant-induced systemic resistance. Conclusions Our findings suggest that bacteria with low abundance play an important role in synthetic communities and that only a few bacterial taxa enriched in diseased roots are associated with disease resistance. Therefore, the construction and simplification of synthetic communities found in the present study could be a strategy employed by plants to adapt to environmental stress.

Disentangling leaf-microbiome interactions in Arabidopsis thaliana by network mapping

“…Even one single bacterial genus (Variovorax) has an ability to maintain root growth in a complex microbiome [56]. A simpli ed SynComs is able to rescue plant from root rot disease [57]. Heritable hubs may serve as the components in the SynComs system in the future research on plant-microbe interactions.…”

Disentangling leaf-microbiome interactions inArabidopsis thalianaby network mapping

“…Even one single bacterial genus (Variovorax) has an ability to maintain root growth in a complex microbiome (56). A simplified SynComs is able to rescue plant from root rot disease (57). Heritable hubs may serve as the components in the SynComs system in the future research on plant–microbe interactions.…”

Comparative Analysis of the Microbial Community Structures Between Healthy and Anthracnose-Infected Strawberry Rhizosphere Soils Using Illumina Sequencing Technology in Yunnan Province, Southwest of China

“…RR18 was the most effective isolate; RR18 had activities, such as reduced collar rot disease incidence, increased germination rate and biomass of peanut seeds, and increased broad-spectrum antifungal activity. Li et al ( 2021c ) study revealed that after Astragalus mongholicus root infected by F. oxysporum , the plant roots can recruit some beneficial microbes, including Pseudomonas, Strenotrophomonas, Chryseobacterium, Achromobacter , and Flavobacterium . Wu et al ( 2021 ) investigated the differences between Chinese wheat yellow mosaic resistant and susceptible wheat root endosphere and rhizosphere microbial, and the results revealed that beneficial rhizosphere microbes, such as Xanthomonadales, Actinomycetales, Sphingomonas, Rhizobium, Bacillaceae, Bacillus, Streptomycetaceae, Streptomyces, Nocardioides, Pseudonocardia, Bradyrhizobium, Pseudonocardiaceae , and Solibacteraceae , were enriched in the resistant wheat root.…”