Data from: The effect of rhizosphere microbes outweighs host plant genotype in reducing insect herbivory

Rhizosphere microbes affect plant performance, including plant resistance
against insect herbivores; yet, a direct comparison of the relative
influence of rhizosphere microbes vs. plant genotype on herbivory levels
and on metabolites related to defense is lacking. In the crucifer Boechera
stricta, we tested the effects of rhizosphere microbes and plant genotype
on herbivore resistance, the primary metabolome, and select secondary
metabolites. Plant populations differed significantly in the
concentrations of 6 glucosinolates (GLS), secondary metabolites known to
provide herbivore resistance in the Brassicaceae. The population with
lower GLS levels experienced ~60% higher levels of aphid (Aphis spp.)
attack; no association was observed between GLS and damage by a second
herbivore, flea beetles (Altica spp.). Rhizosphere microbiome (disrupted
vs. intact native microbiome) had no effect on plant GLS concentrations.
However, aphid number and flea beetle damage were respectively ~3-fold and
7-fold higher among plants grown in the disrupted vs. intact native
microbiome treatment. These differences may be attributable to shifts in
primary metabolic pathways previously implicated in host defense against
herbivores, including increases in pentose and glucoronate interconversion
among plants grown with an intact microbiome. Further, native microbiomes
with distinct community composition (as estimated from 16s rRNA amplicon
sequencing) differed 2-fold in their effect on host plant susceptibility
to aphids. The findings suggest that rhizosphere microbes, including
distinct native microbiomes, can play a greater role than plant genotype
in defense against insect herbivores, and act through metabolic mechanisms
independent of plant genotype.