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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #334815

Research Project: Sunflower Genetic Improvement with Genes from Wild Crop Relatives and Domesticated Sunflower

Location: Sunflower and Plant Biology Research

Title: Development and dissection of diagnostic SNP markers for the downy mildew resistance genes PlArg and Pl8 and maker-assisted gene pyramiding in sunflower (Helianthus annuus L.)

Author
item Qi, Lili
item Talukder, Zahirul - North Dakota State University
item Hulke, Brent
item Foley, Michael

Submitted to: Molecular Genetics and Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2017
Publication Date: 2/3/2017
Citation: L.Qi, L., Talukder, Z.I., Hulke, B.S., Foley, M.E. 2017. Development and dissection of diagnostic SNP markers for the downy mildew resistance genes PlArg and Pl8 and maker-assisted gene pyramiding in sunflower (Helianthus annuus L.). Molecular Genetics and Genomics. 292(3):551-563.

Interpretive Summary: Downy mildew (DM), which is caused by fungus Plasmopara halstedii (Farl.) Berlese & de Toni, is one of the most important diseases that affect sunflower production globally. Amongst the various strategies for downy mildew control, host plant resistance is often the first choice because it is the most effective, economical, and environmentally sustainable approach. Two downy mildew resistance genes, PlArg and Pl8, were discovered in the late 1980s. Over two decades, PlArg is still effective against all known DM pathotypes identified to date, whereas Pl8 confers resistance to 96 % of DM pathotypes. Known DNA markers for PlArg and Pl8 are mostly simple sequence repeat (SSR) markers, the use of which is generally labor and time consuming. In this study, we developed diagnostic single nucleotide polymorphism (SNP) markers for Plarg and Pl8. These SNP markers will facilitate high-throughput and low-cost genotyping for marker-assisted selection in sunflower breeding programs. We also developed sunflower lines with homozygous, three gene pyramids carrying PlArg, Pl8, and the sunflower rust resistant gene R12. These were selected using the linked SNP markers from a segregating F2 population of RHA 340 (carrying Pl8)/ RHA 464 (carrying PlArg and R12). The pyramided sunflower lines will potentially provide durable resistance to downy mildew and rust.

Technical Abstract: Downy mildew, which is caused by fungus Plasmopara halstedii (Farl.) Berlese & de Toni, is one of the most important diseases that affect sunflower production globally. Two downy mildew resistance genes, PlArg and Pl8, were discovered in the late 1980s. Over two decades, PlArg is still effective against all known P. halstedii races identified to date, and Pl8 confers resistance to 96 % of the P. halstedii isolates recently collected in the USA. PlArg and Pl8 have been previously mapped to the linkage groups 1 and 13, respectively, of the sunflower genome using simple sequence repeat (SSR) markers. In this study, we developed high-density single nucleotide polymorphism (SNP) maps encompassing the Plarg and Pl8 genes and identified diagnostic SNP markers closely linked to these genes. The flanking SNP markers NSA_007595 and NSA_001835 delimited PlArg to an interval of 2.83 Mb and the SNP markers SFW01497 and SFW06597 delimited Pl8 to an interval of 2.85 Mb on the physical map of the sunflower genome. The specificity of the diagnostic markers was validated in a highly diverse panel of 548 sunflower lines. We also developed sunflower lines with homozygous, three gene pyramids carrying PlArg, Pl8, and the sunflower rust resistant gene R12. These were selected using the linked SNP markers from a segregating F2 population of RHA 340 (carrying Pl8)/ RHA 464 (carrying PlArg and R12). The pyramided sunflower lines will potentially provide durable resistance to downy mildew and rust.