Bivariate analysis of barley scald resistance with relative maturity reveals a new major QTL on chromosome 3H

Abstract

AbstractThe disease scald of barley is caused by the pathogen Rhynchosporium commune and can cause up to 30-40% yield loss in susceptible varieties. In this study, the Australian barley cultivar Yerong was demonstrated to have resistance that differed from Turk (Rrs1) based on seedling tests with 11 R. commune isolates. A doubled haploid population with 177 lines derived from a cross between Yerong and Franklin was used to identify quantitative trait loci (QTL) for scald resistance. Scald resistance against four pathogen isolates was assessed at the seedling growth stage in a glasshouse experiment and at the adult growth stage in field experiments with natural infection over three consecutive years. A QTL on chromosome 3H was identified with large effect, consistent with a major gene conferring scald resistance at the seedling stage. Under field conditions, scald percentage was negatively correlated with early relative maturity. A bivariate analysis was used to model scald percentage and relative maturity together, residuals from the regression of scald percentage on relative maturity were used as our phenotype for QTL analysis. This analysis identified one major QTL on chromosome 3H, which mapped to the same position as the QTL identified for scald resistance at seedling stage. The identified QTL on 3H is proposed to be different from the Rrs1 on the basis of seedling resistance against different R. commune isolates and physical map position. The analysis also identified an additional novel QTL on chromosome 7H. This study increases the current understanding of scald resistance and identifies genetic material possessing QTLs useful for the marker-assisted selection of scald resistance in barley breeding programs.