Mapping and candidate gene identification of loci determining tolerance to greenbug (Schizaphis graminum, Rondani) in barley

Greenbug is one of the most aggressive pests of barley and wheat. In Argentina, yield losses of wheat, barley, oat and sorghum crops caused by greenbug are chronic and at times severe. Since Marker Assisted selection for greenbug resistance genes in barley is very limited, the purpose of the current study was to map greenbug resistance genes in doubled haploid (DH) lines and to identify candidate genes. A set of DH lines of the Oregon-Wolfe Barley (OWB) mapping population derived from the cross between OWB_DOM and OWB_REC and both parental lines were screened for tolerance to greenbug. There was significant variation among the DH lines in foliar area (FA), dry weight (DW) and chlorophyll contents (Ch) between infested and control DH lines. Three main QTLs were identified. These QTLs explained 82 % of the FA, 80 % of DW and 58 % of Ch variability of infested plants. The initial and final FA and DW of controls and final DW of infested plants were associated with the same molecular markers on chromosome 2H (Vrs1, BmAc0144f, GBR259, GBS705). The final FA of infested plants was significantly linked to molecular markers on chromosome 5H (GBRO986, GBR518, GBM1483, GBR1082). The positive alleles were provided by OWB_DOM. The content of chlorophyll of infested plants was associated with the marker loci Ris44, GBR1608, GBR1637N and GBS0785 on chromosome 7H, with the positive alleles provided by OWB_REC. Both parents contributed to different tolerance traits. The QTLs found in this population are new greenbug resistance loci. A sequence homology search was performed to derive the putative function of the genes linked to the QTLs.