Quantitative trait loci for scald resistance in barley localized by a non-interval mapping procedure

Three quantitative trait loci (QTL) for scald resistance in barley were identified and mapped in relation to molecular markers using a population of chromosome doubled-haploid lines produced from the F, generation of a cross between the spring barley varieties 'Alexis' and 'Regatta'. Two field experiments Acre conducted in Denmark and two in Norway to assess disease resistance, The percentage leaf area covered with scald (Rhynchosporium secalis) ranged from 0 to 40% in the 189 doubled-haploid (DH) lines analysed. One quantitative trait locus was localized in the centromeric region of chromosome 3H. Qryn3, using the MAPQTL program, MAPQTL was unable to provide proper localization of the other two resistance genes and so a noninterval QTL mapping method was used. One v as found to he located distally to markers on chromosome 4H (Qryn4) and the other. Qryn6. was located distally to markers on chromosome 6H. The effects of differences between the Qryn3. Qryn4 and Qryn6 alleles in two barley genotypes for the QTL Acre estimated to be 8.8%. 7.3% and 7.0%. respectively. of leaf covered by scald. No interactions between the QTLs were found.