Characterization and mapping of a downy mildew resistance gene, , in sunflower ( L.).

Unlabelled: Downy mildew (DM) is one of the most serious diseases in sunflower-growing regions worldwide, often significantly reducing sunflower yields. The causal agent of sunflower DM, the oomycete pathogen , is highly virulent and aggressive. Studying regional disease spread and virulence evolution in the DM pathogen population is important for the development of new sunflower inbred lines with resistance to the existing DM pathogen. The sunflower line 803-1, as one of nine international differential hosts, has been used in the identification of virulent pathotypes in sunflower since 2000. The DM resistance gene in 803-1 was temporally designated  + based on allelic analysis but has not been molecularly characterized. In the present study, bulked segregant analysis and genetic mapping confirmed the presence of the gene within a large gene cluster on sunflower chromosome 13 in 803-1, as previously reported. Subsequent saturation mapping in the gene target region with single nucleotide polymorphism (SNP) markers placed this gene at an interval of 3.4 Mb in the XRQ reference genome assembly, a location different from that of . Therefore, the gene in 803-1 was re-designated because it is not allelic with . Four SNP markers co-segregated with , and SNP SFW05743 was 1.1 cM proximal to . The relationship of eight genes in the cluster is discussed based on their origin, map position, and specificity of resistance/susceptibility to DM infection.

Supplementary Information: The online version contains supplementary material available at 10.1007/s11032-022-01280-1.