Volume 28, Issue 7
ORIGINAL ARTICLE

The effect of rhizosphere microbes outweighs host plant genetics in reducing insect herbivory

Charley J. Hubbard

Corresponding Author

E-mail address: charleyjhubbard@gmail.com

Department of Botany, University of Wyoming, Laramie, Wyoming

Program in Ecology, University of Wyoming, Laramie, Wyoming

Correspondence

Charley J. Hubbard, Department of Botany, University of Wyoming, Laramie, WY.

Email: charleyjhubbard@gmail.com

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Baohua Li

Plant Sciences, University of California, Davis, Davis, California

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Robby McMinn

Department of Botany, University of Wyoming, Laramie, Wyoming

Program in Ecology, University of Wyoming, Laramie, Wyoming

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Marcus T. Brock

Department of Botany, University of Wyoming, Laramie, Wyoming

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Lois Maignien

Marine Biological Laboratory, Josephine Bay Paul Center, Woods Hole, Massachusetts

Laboratory of Microbiology of Extreme Environments, UMR 6197, Institut Européen de la Mer, Université de Bretagne Occidentale, Plouzane, France

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Brent E. Ewers

Department of Botany, University of Wyoming, Laramie, Wyoming

Program in Ecology, University of Wyoming, Laramie, Wyoming

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Daniel Kliebenstein

Plant Sciences, University of California, Davis, Davis, California

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Cynthia Weinig

Department of Botany, University of Wyoming, Laramie, Wyoming

Program in Ecology, University of Wyoming, Laramie, Wyoming

Department of Molecular Biology, University of Wyoming, Laramie, Wyoming

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First published: 24 December 2018
Citations: 8

Abstract

Rhizosphere microbes affect plant performance, including plant resistance against insect herbivores; yet, a direct comparison of the relative influence of rhizosphere microbes versus plant genetics on herbivory levels and on metabolites related to defence is lacking. In the crucifer Boechera stricta, we tested the effects of rhizosphere microbes and plant population on herbivore resistance, the primary metabolome, and select secondary metabolites. Plant populations differed significantly in the concentrations of six glucosinolates (GLS), secondary metabolites known to provide herbivore resistance in the Brassicaceae. The population with lower GLS levels experienced ~60% higher levels of aphid (Myzus persicae) attack; no association was observed between GLS and damage by a second herbivore, flea beetles (Phyllotreta cruciferae). Rhizosphere microbiome (disrupted vs. intact native microbiome) had no effect on plant GLS concentrations. However, aphid number and flea beetle damage were respectively about three‐ and seven‐fold higher among plants grown in the disrupted versus intact native microbiome treatment. These differences may be attributable to shifts in primary metabolic pathways previously implicated in host defence against herbivores, including increases in pentose and glucoronate interconversion among plants grown with an intact microbiome. Furthermore, native microbiomes with distinct community composition (as estimated from 16s rRNA amplicon sequencing) differed two‐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 population in defence against insect herbivores, and act through metabolic mechanisms independent of population.

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