Resistance to barley scald (Rhynchosporium secalis) in the Ethiopian donor lines 'Steudelli' and 'Jet', analyzed by partial least squares regression and interval mapping

Summary

The resistance of barley (Hordeum vulgare L.) to Rhynchosporium secalis (scald) has been investigated in two crosses between the susceptible cv. 'Ingrid' and two resistant Ethiopian landraces, 'Steudelli' and 'Jet'. Doubled haploids were inoculated in replicated tests using two isolates of R. secalis, '4004' and 'WRS1872'. Expression of resistance differed widely between replicated tests. AFLP, SSR and RFLP markers wereused to develop chromosome maps. Results have been analysed using partial least squares regression (PLSR) and intervalmapping. In PLSR the major covariance structures or 'latent variables' between X (markers) and Y (isolates, tests) are modelled as principal components and their optimal number determined by cross-validation. In 'Steudelli' two QTL were detected, one on each of chromosomes 3H and 7H, in 4 out of 5 tests, while in 'Jet' only one (different) allele at the 3H locus was found. The validated R2 varied between 11.0% and 64.9% inthe replicated tests with '4004'.With isolate 'WRS1872' the 7H locus and another 3H locus were detected. By interval mappingthe QTL detected were less stable and generally gave lower R2values than PLSR. PLSR does not depend on maps, but intervalmapping based on values predicted by PLSR had R2 around 90%.Itis suggested that PLSR may be a useful tool in QTL analysis.