Soil health is dependent on its diverse communities of microbes. Many of these
microorganisms enhance plant growth and enrich the soil. However, the
interactions between communities of beneficial microbes remain unclear.
Arbuscular mycorrhizal fungi (AMF) are responsible for the most prolific beneficial
plant-fungal interaction. However, their influence on the diverse range of plant
growth promoting rhizobacteria (PGPR) that also associate with plant roots is yet
to be fully elucidated. This research investigates the tripartite interactions
between host plant-AMF-PGPR using next-generation sequencing and culture-
dependent methodology to define the effect of AMF inoculation on the taxonomic
and functional characteristics of the bacterial assemblage of the root microbiome
of white clover (Trifolium repens). Soil from two land use types (grassland and
bare fallow) amended with fertiliser and/or AMF inoculants are used to describe
the effect of these management components on the function of beneficial
microbes in cropping systems.
The AMF Funneliformis geosporum affected the taxonomic composition of
bacteria in the rhizosphere but not the rhizoplane. However, soil type and fertiliser
were more influential determinants of bacterial taxa and function. Using split-root
microcosm experiments with root exclusion meshes, the dispersal of bacteria was
observed in the absence of AMF hyphae. The approaches were combined to
show that root microbiome establishment is independent of AMF hyphal
facilitation or selection of beneficial bacterial traits or taxa.
In vitro predictive measures were used to design a putative Phosphorus
solubilising consortium comprised of synergistic P-solubilising rhizobacteria and
AMF. Plant health parameters were influenced by the addition of Ca₃PO₄ but
were unaffected by any microbial combination. The performance of a putative
bioinoculant is dependent on many external factors which can negatively impact
the intended function.
This work is an important indicator of the complexity of the soil microbiome and
demonstrates the profound influence of agronomic inputs on microbial function.Harris, Jim (Associate)PhD in Environment and Agrifoo
