TY - JOUR

T1 - Defence gene expression and phloem quality contribute to mesophyll and phloem resistance to aphids in wild barley

AU - Leybourne, Daniel J.

AU - Valentine, Tracy A.

AU - Robertson, Jean A.H.

AU - Pérez-Fernández, Estefania

AU - Main, Angela M.

AU - Karley, Alison J.

AU - Bos, Jorunn I.B.

N1 - Funding Information: DJL was funded by the James Hutton Institute and the Universities of Aberdeen and Dundee through a Scottish Food Security Alliance (Crops) PhD studentship. AJK, TAV, AHJR, AMM, and EP-F were supported by the strategic research programme funded by the Scottish Government’s Rural and Environment Science and Analytical Services Division. JIBB was supported by the European Research Council (310190-APHIDHOST). We would like to thank Dr Freddy Tjallingii (EPG Systems, The Netherlands), Professor Alberto Fereres (CSIC, Spain),and Professor Gregory Walker (University of California,Riverside, USA) for providing EPG training, and Gaynor Malloch (James Hutton Institute) for kindly providing COI barcoding primers.

PY - 2019/8/1

Y1 - 2019/8/1

N2 - 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.

AB - 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.

KW - Amino acid composition

KW - defence gene expression

KW - electrical penetration graph (EPG)

KW - Hordeum spontaneum

KW - partial resistance

KW - Rhopalosiphum padi

KW - Sitobion avenae

KW - Utamphorophora humboldti

UR - http://www.scopus.com/inward/record.url?scp=85071346696&partnerID=8YFLogxK

U2 - 10.1093/jxb/erz163

DO - 10.1093/jxb/erz163

M3 - Article

C2 - 31173098

AN - SCOPUS:85071346696

VL - 70

SP - 4011

EP - 4026

JO - Journal of experimental botany

JF - Journal of experimental botany

SN - 0022-0957

IS - 15

ER -