Mapping quantitative trait loci for resistance against Russian wheat aphid (Diuraphis noxia) in wheat (Triticum aestivum L.)

Diuraphis noxia (Russian wheat aphid, RWA), one of the most aggressive pests of wheat, has evolved several biotypes with virulence matching known Dn resistance genes. This paper was aimed at determining the location of plant-defence genes triggered by RWA in a set of doubled haploid (DH) lines obtained from the cross of winter wheat varieties 'Spark' and 'Rialto'. Both parental lines, 110 DH and CItr2401 (a RWA-resistant line) were screened for antixenosis, tolerance and antibiotic mechanisms of resistance with a population of RWA collected in Argentina. Antixenosis was not significantly linked to any marker locus. Tolerance traits showed significant associations with several chromosomes. Quantitative trait loci (QTL) for the foliar area developed during infestation was significantly associated with marker loci Xpsp3103 on 4DS, and Xgdm3 on 5DS. QTL for chlorophyll content in the infested plants were significantly associated with the marker loci Xgwm533 on 3BS and Xpsp3094 on 7AL, and a QTL for the number of expanded leaves was associated with the marker loci Xwmc264 on 3AS and XwPt8836 on 4DS. QTL for most of the tolerance traits were significantly associated with the same chromosome intervals on chromosomes 4DS and 5DS. The 4DS QTL were linked to or had a pleiotropic effect on Rht-D1. Most of the antibiosis traits were significantly associated with the same marker loci on chromosomes 4A (XwPt7405), 1B (XwPt9032) and 5B (Xbarc109 and Xbarc74). Several novel genes conferring tolerance and antibiosis to RWA were identified and these could be transferred into wheat cultivars to enlarge the genetic base of defence against this aphid pest. These new genes can be designated as QDn.unlp genes, following the rules for gene nomenclature in wheat.