Molecular dissection of resistance gene cluster and candidate gene identification of Pl17 and Pl19 in sunflower by whole-genome resequencing

Authors: MA, G. - North Dakota State University; Song, Qijian; Underwood, William; ZHANG, Z. - North Dakota State University; Fiedler, Jason; XUEHUI, LI - North Dakota State University; Qi, Lili

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2019
Publication Date: 10/18/2019
Citation: Ma, G.J., Song, Q., Underwood, W., Zhang, Z.W., Fiedler, J.D., Xuehui, L., Qi, L. 2019. Molecular dissection of resistance gene cluster and candidate gene identification of Pl17 and Pl19 in sunflower by whole-genome resequencing. Scientific Reports. 9:14974. https://doi.org/10.1038/s41598-019-50394-8.
DOI: https://doi.org/10.1038/s41598-019-50394-8

Interpretive Summary: Sunflower is an important economic crop worldwide because of its oil products and edible seeds. Downy mildew (DM) is a disease that severely challenges global sunflower production. Due to environmental and economic concerns, utilization of host resistance is among the best tactics to control disease infestations. Two prerequisites are essential for the use of host resistance, i.e., a resistance resource (resistance genes) and tools (diagnostic markers) used in breeding programs. In this study, we report the fine mapping of the two broad-spectrum DM resistance genes, Pl17 and Pl19, and the development of diagnostic markers for these genes in sunflower. Diagnostic markers identified for Pl17 and Pl19 will be useful for transferring these resistance genes into elite sunflower lines and pyramiding them with other broadly effective DM genes for durable control. Candidate genes for Pl17 and Pl19 were also identified, thus laying the foundation for uncovering molecular mechanisms of host-pathogen interactions.

Technical Abstract: Sunflower (Helianthus annuus L.) production is challenged by different biotic and abiotic stresses, among which downy mildew (DM) is a severe biotic stress that is detrimental to sunflower yield and quality in many sunflower-growing regions worldwide. Resistance against its infestation in sunflower is commonly regulated by single dominant genes. Pl17 and Pl19 are two broad-spectrum DM resistance genes that have been previously mapped to a gene cluster spanning a 3.2 Mb region at the up end of sunflower chromosome 4. Using a whole-genome resequencing approach combined with a reference sequence-based chromosome walking strategy and high-density mapping populations, we narrowed down Pl17 to a 15-kb region flanked by SNP markers C4_5711524 and SPB0001. The candidate gene HanXRQChr04g0095641 for Pl17 was identified, encoding a typical TNL resistance gene protein. Pl19 was found to be a 35-kb region and approximately 1 Mb away from Pl17, flanked by SNP markers C4_6676629 and C4_6711381. Candidate gene HanXRQChr04g0095951 for Pl19 was predicted to encode an RNA methyltransferase family protein. Six and eight SNP markers diagnostic for Pl17 and Pl19, respectively, were identified upon evaluation of 96 diverse sunflower lines, providing a very useful tool for marker-assisted selection in sunflower breeding programs.