High-density mapping and candidate gene analysis of Pl18 and Pl20 in sunflower by whole-genome resequencing

Authors: MA, GUOJIA - North Dakota State University; SONG, QIJIAN - North Dakota State University; LI, XUEHUI - North Dakota State University; Qi, Lili

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/11/2020
Publication Date: 12/16/2020
Citation: Ma, G., Song, Q., Li, X., Qi, L. 2020. High-density mapping and candidate gene analysis of Pl18 and Pl20 in sunflower by whole-genome resequencing. International Journal of Molecular Sciences. 21(24):9571. https://doi.org/10.3390/ijms21249571.
DOI: https://doi.org/10.3390/ijms21249571

Interpretive Summary: Sunflower is one of the seven important oilseed crops worldwide, and its oil consists of high percentages of linoleic and monounsaturated fats, which provides many health benefits. Downy mildew (DM) is a devastating disease impairing sunflower production, and breeding varieties resistant to DM is the best strategy to control this disease. In the present study, we fine-mapped two broad-spectrum DM resistance genes, Pl18 and Pl20, in sunflower and identified candidate genes for Pl18 and Pl20. In addition, a total of 13 diagnostic markers for Pl18 and four for Pl20 were identified, respectively. These markers are valuable resources to efficiently and accurately transfer these new genes to elite sunflower lines and to combine these and other broad-spectrum DM resistance genes for long-lasting disease control.

Technical Abstract: Downy mildew (DM) is one of the severe biotic threats to sunflower production worldwide. The inciting pathogen, Plasmopara halstedii, could overwinter in the field for years, creating a persistent threat to sunflower. The dominant genes Pl18 and Pl20 conferring resistance to known DM races have been previously mapped to 1.5 and 1.8 cM intervals on sunflower chromosomes 2 and 8, respectively. Utilizing a whole genome resequencing strategy combined with reference sequence-based chromosome walking and high-density mapping in the present study, Pl18 was placed in a 0.7 cM interval on chromosome 2. A candidate gene HanXRQChr02g0048181 for Pl18 was identified from the XRQ reference genome and predicted to code protein with typical NLR domains for disease resistance. The Pl20 gene was placed in a 0.2 cM interval on chromosome 8. The putative gene with the NLR domain for Pl20, HanXRQChr08g0210051, was identified within the Pl20 interval. SNP markers closely linked to Pl18 and Pl20 were evaluated with 96 diverse sunflower lines, and a total of 13 diagnostic markers for Pl18 and four for Pl20 were identified. These markers will facilitate to transfer these new genes to elite sunflower lines and to pyramid these genes with broad-spectrum DM resistance in sunflower breeding.