Quantitative trait locus analysis of spot blotch and leaf rust resistance in the BCD47 × Baronesse barley mapping population

With 2 figures and 6 tables Abstract We studied the genetics of the resistance to leaf rust (LR) (caused by Puccinia hordei) and spot blotch (SB) (caused by Cochliobolus sativus) in barley using a doubled‐haploid population derived from the cross BCD47 × Baronesse. BCD47 has low SB severity and high susceptibility to LR, while Baronesse is susceptible to SB and has low LR severity. Resistance to both diseases is expressed at the adult plant stage. The population was phenotyped in eight field environments for SB and nine for LR. Ten quantitative trait loci (QTLs) were detected for SB. None were significant in more than three environments, and both parents contributed resistance alleles. Five QTLs were detected for LR. The most consistent quantitative trait locus (QTL) (significant in seven environments) was on chromosome 6H (located on the Bmag173‐Bmag009 interval) with Baronesse contributing the resistance allele. Coincident QTL effects for SB were also detected in this region with resistance alleles to the two diseases in repulsion. These results illustrate the difficulties of resistance gene detection in the complex disease environments found under field conditions.