Beneficial ecological networks dominate the dynamic root endosphere microbiome during long-term symbiosis with host plants

Endophytes could assist the host plant in the acquisition of nutrients and tolerance of stresses during their long symbiotic life cycle with the host plant. Blueberry (Vaccinium spp.) is adapted to acidic soils and can inhabit harsh soil conditions. However, the dynamic variation of its endosphere microbial community under long-term cultivation remains unclear.

We collected blueberry root samples of four age groups (4a, 8a, 17a, and 33a). The diversity and composition of bacterial and fungal communities in the root endosphere were analyzed, and their co-occurrence networks were constructed to explore interkingdom interactions and keystone taxa.

As the major phylum of the endosphere, the relative abundance of Actinobacteria decreased with the age of the blueberry, whereas Proteobacteria increased. The fungal communities were dominated by Sordariomycetes, Eurotiomycetes, and Agaricomycetes, and these were not regularly altered with the increased blueberry age. The co-occurrence network revealed that positive interactions were observed in the bacterial and fungal communities and were consistently dominant within both intrakingdom and interkingdom networks. Among the interkingdom network, keystone taxa were identified for bacteria mainly belonging to Proteobacteria and Actinobacteria of bacteria, as well as for fungi of Ascomycota, which have potentially beneficial effects on host plants.

Our study reveals although the diversity and composition varied with blueberry age in the root endosphere, their positive interactions of intrakingdom or interkingdom consistently dominate the network, and it may be such positive beneficial interactions that maintain the health of host plant during long-term symbiosis.