Quantitative trait locus for resistance to the aphid Rhopalosiphum padi L. in barley (Hordeum vulgare L.) is not linked with a genomic region for gramine concentration

Abstract

Gramine is an indole alkaloid found in certain grass species. Results of previous studies have diverged as to whether this compound might cause resistance to aphids or not. In a breeding program aiming to introduce resistance to the cereal pest Rhopalosiphum padi L. in barley, a cultivar has been crossed with the progenitor of cultivated barley, Hordeum vulgare ssp. spontaneum, and an F 1-derived population of doubled haploid (DH) lines was screened both for seedling gramine concentration and resistance to R. padi. The resistance was measured as individual aphid growth in the laboratory. The present study aims to determine if there is a genetic relationship between aphid growth retardation and gramine concentration. To do so, the lines were genotyped with a 384 SNP oligonucleotide pool assay and QTL analyses were performed for both traits. A previously identified aphid resistance locus on the distal part of chromosome 2HS was thereby confirmed, with resistance inherited from H. v. ssp. spontaneum, whereas one or more QTL for gramine concentration were potentially indicated on chromosome 3H, thus corroborating that the two traits are not linked genetically.

Applications of the indole-alkaloid gramine modulate the assembly of individual members of the barley rhizosphere microbiota

“…The genus Hordeum has evolved two main indole alkaloids with allelopathic and defensive functions, the benzoxazinoid DIBOA and gramine, whose biosynthesis appear mutually exclusive within barley lineages ( Grün, Frey & Gierl, 2005 ). In particular, gramine is the main allelochemical of the lineage H. vulgare which has historically been implicated in defensive responses against insects ( Corcuera, 1993 ; Cai et al, 2009 ; Sun et al, 2013 ), as well as foliar pathogens ( Sepulveda & Corcuera, 1990 ; Matsuo et al, 2001 ) although the genetic basis of this trait appears complex ( Åhman, Tuvesson & Johansson, 2000 ; Macaulay, Ramsay & Åhman, 2020 ). Intriguingly, crop selection left a footprint on the biosynthesis of this secondary metabolite: modern cultivated, so called ‘elite’, varieties ( H. vulgare subp .…”

Genetic Resources of Cereal Crops for Aphid Resistance

“…At the same time, an analysis of 150 doubled haploid barley lines obtained from the crossing of “Steptoe” (high content of gramine) and “Morex” (traces of gramine) showed that the grm gene, which controls the synthesis of gramine in the seedling phase, is localized on chromosome 5 and is not linked to minor genes of resistance to grain aphids localized on chromosomes 2 and 5 [ 63 , 64 ]. An analysis of another series of doubled haploid lines also showed that QTLs, which control resistance to R. padi and the content of gramine in plants, are not linked [ 65 ].…”