Genome-wide association mapping for seedling and adult resistance to powdery mildew in barley

Abstract

Key message
Two new major QTL were identified for powdery mildew resistance. We confirmed that the QTL on 7HS contributed mainly to the adult-plant resistance, while another one on chromosome arm 1HS made a significant contribution to the seedling resistance.

Abstract
Powdery mildew (PM), caused by Blumeria hordei, can occur at all post emergent stages of barley and constantly threatens crop production. To identify more genes for efective resistance to powdery mildew for use in breeding programs, 696 barley accessions collected from diferent regions of the world were evaluated for PM resistance at seedling and adult growth stages in three diferent states of Australia. These barley accessions were genotyped using DArTSeq with over 18,000 markers for a genome-wide association study (GWAS). Using the FarmCPU model, 54 markers showed signifcant associations with PM resistance scored at the seedling and adult-plant stages in diferent states of Australia. Another 40 markers showed tentative associations (LOD>4.0) with resistance. These markers are distributed across all seven barley chromosomes. Most of them were grouped into eleven QTL regions, coinciding with the locations of most of the reported resistance genes. Two major MTAs were identifed on chromosome arms 3HS and 5HL, with one on 3HS contributing to adult plant resistance and the one on 5HL to both seedling and adult plant resistance. An MTA on 7HS contributed mainly to the adult-plant resistance, while another one on chromosome arm 1HS made a signifcant contribution to the seedling resistance.