Abstract
BackgroundPlant 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.ResultsFusarium 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.ConclusionsOur 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.-VujMZjCpFzTumqS8Rf9nHVideo abstract
Highlights
Plant health and growth are negatively affected by pathogen invasion; plants can dynamically modulate their rhizosphere microbiome and adapt to such biotic stresses
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
SCI could decrease the incidence of Astragalus root rot disease, we found that the synthetic community containing four species had the same effect on root rot disease control
Summary
Plant health and growth are negatively affected by pathogen invasion; plants can dynamically modulate their rhizosphere microbiome and adapt to such biotic stresses. Soil diseasesuppressive capacity could be augmented by soil suspension inoculation, and disease-suppressive soil can be converted into susceptible soil by sterilization [15] Such phenomena attribute to the enrichment of specific microorganisms in the rhizosphere of plant roots, as these microorganisms may participate in the resistance to the invasion of pathogens [2]. Under the induction of environmental factors, the physiological status and metabolic pathway of plants changed, which influences the proportions and compositions of rhizodeposits, including root exudates and complex organic compounds resulting from sloughed-off root tissues [16] Such rhizodeposits released by roots attract specific microorganisms from the soil to colonize the rhizosphere and roots. The assembled microbial communities are not able to suppress disease when the plants are initially infected by pathogens; root-associated microbial communities could suppress diseases after successive pathogen infestation events
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
