Defence gene expression and phloem quality contribute to mesophyll and phloem resistance to aphids in wild barley

Daniel J. Leybourne, Tracy A. Valentine, Jean A. H . Robertson , Estefania Pérez-Fernández, Angela M . Main , Alison J. Karley, Jorunn I. B. Bos (Lead / Corresponding author)

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
31 Downloads (Pure)

Abstract

Aphids, including the bird cherry-oat aphid (Rhopalosiphum padi), are significant agricultural pests. The wild relative of barley, Hordeum spontaneum 5 (Hsp5), has been described to be partially resistant to R. padi, with this resistance proposed to involve higher thionin and lipoxygenase gene expression. However, the specificity of this resistance to aphids and its underlying mechanistic processes are unknown. In this study, we assessed the specificity of Hsp5 resistance to aphids and analysed differences in aphid probing and feeding behaviour on Hsp5 and a susceptible barley cultivar (Concerto). We found that partial resistance in Hsp5 to R. padi extends to two other aphid pests of grasses. Using the electrical penetration graph technique, we show that partial resistance is mediated by phloem- and mesophyll-based resistance factors that limit aphid phloem ingestion. To gain insight into plant traits responsible for partial resistance, we compared non-glandular trichome density, defence gene expression, and phloem composition of Hsp5 with those of the susceptible barley cultivar Concerto. We show that Hsp5 partial resistance involves elevated basal expression of thionin and phytohormone signalling genes, and a reduction in phloem quality. This study highlights plant traits that may contribute to broad-spectrum partial resistance to aphids in barley.

Original languageEnglish
Pages (from-to)4011-4026
Number of pages16
JournalJournal of Experimental Botany
Volume70
Issue number15
Early online date10 Apr 2019
DOIs
Publication statusPublished - 1 Aug 2019

Keywords

  • Amino acid composition
  • Hordeum spontaneum
  • Rhopalosiphum padi
  • Sitobion avenae
  • Utamphorophora humboldti
  • defence gene expression
  • electrical penetration graph (EPG)
  • partial resistance

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