Rhizosphere Microbiome of Forest Trees Determines Their Resistance to Soil-borne Pathogens

Abstract

Background and aimsThe ability of plants to cope with environmental pressure and the interaction between rhizosphere microorganisms and host trees play an important role in the stability and function of forest ecosystems. Beneficial microbes recruited to the plant rhizosphere and stably association with tree roots can potentially reduce biotic stress, but the biochemical processes involved in coping with pathogen attack are not fully understood. Here, we aimed to investigate the ecology process of rhizosphere microbiota from four broad-leaved and three coniferous tree varieties involving in the suppression of soil-borne fungal pathogens. MethodsWe used separation cultivation and in vitro antagonistic experiments to investigate the inhibitory effects of rhizosphere microbiome on pathogenic fungi. Rhizosphere microbiome was then sequenced using the Illumina MiSeq platform, and root exudates of trees were measured by gas chromatography-mass spectrometry (GC-MS).ResultsRhizosphere microbes from seven tree varieties had strong inhibitory effects on fungal pathogens, nevertheless, there were significant differences in their capacity. The dissimilarities in rhizosphere bacterial communities that were significantly correlated with phylogenetic distance of trees had a greater influence on suppression of pathogens compared with microbial abundance and diversity. Combined analysis of a random forest model and co-occurrence networks, revealed a cooperative relationship between key groups that were positively associated with inhibition of fungal pathogens in the tree rhizosphere. This process was further strengthened by specific metabolites secreted by tree roots. ConclusionsIn general, the rhizosphere microbiota of seven tree species had different inhibitory effects on fungal pathogens, and the cooperative relationship within the rhizosphere microbial community plays an important role in maintaining trees resistance to soil pathogens stress.

Microbiome-Mediated Protection against Pathogens in Woody Plants

“…Conversely, due to long-term interactions between trees and the soil microbiome, trees can establish relatively stable rhizosphere microbiome characteristics and plant functional traits [47,69] that support resistance to biotic stresses from soil-borne pathogens. Taken together, optimizing the tree rhizosphere microbiome may be an effective way to improve forest health [70][71][72].…”

“…Recently, it was demonstrated that infection of citrus trees by Candidatus Liberibacter asiaticus, associated with Huanglongbing (HLB), was shown to drastically alter the composition of citrus communities across the disease spectrum [126]. Moreover, specific compounds in tree root exudates stimulate key rhizosphere bacteria to cooperate in suppressing soil-borne pathogens [72]. The plant microbiome interacts with pathogens directly or indirectly to strengthen pathogen resistance (Figure 2).…”

Microbiome-Mediated Protection against Pathogens in Woody Plants

“…Conversely, due to long-term interactions between trees and the soil microbiome, trees can establish relatively stable rhizosphere microbiome characteristics and plant functional traits [52,74], which enhance biotic stress tolerance against soil-borne pathogens. Taken together, optimizing the tree rhizosphere microbiome may be an effective way to improve forest health [75][76][77].…”

“…Recently, it was demonstrated that the infection of citrus trees by Candidatus Liberibacter asiaticus, associated with HLB, drastically altered the composition of citrus microbiome communities across the disease spectrum [130]. Moreover, specific compounds present in tree root exudates stimulate key rhizosphere bacteria to collaborate in the suppression of soil-borne pathogens [77]. The plant microbiome interacts with pathogens directly or indirectly to strengthen pathogen resistance (Figure 2).…”