Barley Genetics Newsletter 37:5-20 (2007) Frequency distributions and composite interval mapping for QTL analysis in ‘Steptoe’ x ‘Morex’ barley mapping population

With the advancement of QTL mapping strategies, the traditional approaches for the identification of genes and their effects responsible for trait expression are gradually losing significance. The phenotypic data for heading days, plant height, peduncle length, number of tillers and stripe rust was recorded on 150 recombinant inbred line (RIL) population developed from a barley cross of ‘Steptoe’ and ‘Morex’. Preliminary examinations of frequency distribution plots were fairly useful in the prediction of number of genes governing traits expression in barley (Hordeum vulgare L.). The predictions were then systematically confirmed through QTL mapping. Molecular marker data for the population available at the public domain (GrainGenes website) was used for the construction of linkage map and QTL analysis. Clear colinearity was observed between the number of QTLs identified and the number of genes predicted based upon frequency distribution study alone. A total of 17 QTLs were detected for the five traits evaluated. Several major QTLs were detected on chromosome 2H, which could serve as candidate for mapbased studies of phenomena such as pleiotropism, recombination hot spots, gene-rich regions and QTL clustering.