Mapping antixenosis genes on chromosome 6A of wheat to greenbug and to a new biotype of Russian wheat aphid

Greenbug and Russian wheat aphid (RWA) are two devastating pests of wheat. The first has a long history of new biotype emergence and, recently. RWA resistance has just started to break down. Thus, it is necessary to find new sources of resistance that will broaden the genetic base against these pests in wheat. Seventy-five doubled haploid recombinant (DHR) lines for chromosome 6A from the F I of the cross between 'Chinese Spring' and the 'Chinese Spring (Synthetic 6A) (Triticum dicoccoides x Aegilops tauschii)' substitution line were used as a mapping population for testing resistance to greenbug biotype C and to a new strain of RWA that appeared in Argentina in 2003. A quantitative trait locus (QTL) for antixenosis to greenbug was significantly associated with the marker loci Xgwm10009 and Xgwm1185 located in the centromere re-ion of chromosome 6A. Another QTL which accounted for most of the amixenosis against RWA was associated with the marker loci Xgwm1293 and Xgwm1150, both located on the Iona arm of chromosome 6A. This is the first report of greenbug and RWA resistance genes located on chromosome 6A. It is also the first report of antixenosis against the new strain of RWA. As most of the RWA resistance genes present in released cultivars have been located in the D-genome. it is highly desirable to find new Sources in other genomes to combine the existing resistance genes with new Sources.