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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 #308091
Title: Relocation of a rust resistance gene R2 and its marker-assisted gene pyramiding in confection sunflower (Helianthus annuus L.)

Author
item Qi, Lili
item MA, GUOJIA - North Dakota State University
item LONG, YUNMING - North Dakota State University
item GONG, LI - North Dakota State University
item Hulke, Brent
item MARKELL, SAM - North Dakota State University

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2014
Publication Date: 3/1/2015
Citation: Qi, L.L., Ma, G.J., Long, Y.M., Hulke, B.S., Gong, L., Markell, S.G. 2015. Relocation of a rust resistance gene R2 and its marker-assisted gene pyramiding in confection sunflower (Helianthus annuus L.). Theoretical and Applied Genetics. 128(3):477-488. DOI:10.1007/s00122-014-2446-0.

Interpretive Summary: Sunflower seed is the fourth largest source of vegetable oil worldwide, following soybean, palm, and canola (rapeseed). While the majority of sunflower produced in the U.S. is oil-type, 10-20% of production is confection; high value seed product used primarily in human diets as a snack. Rust (caused by Puccinia helianthi Schwein.) is a major yield-limiting disease of sunflower in many sunflower producing countries. The inbred line MC29 carries the rust resistance gene, R2, conferring resistance to numerous races of the rust fungus in the U.S., Canada, and Australia, and can be used as a broad-spectrum resistance resource. Based on phenotypic assessments and simple sequence repeat (SSR) analyses on the 117 F2 individuals derived from a cross of HA 89 with MC29 (USDA), R2 was mapped to linkage group (LG) 14 of the sunflower genome, and not to the previously reported location on LG9. The closest SSR marker HT567 was located at 4.3 cM distal to R2. Furthermore, 36 selected single nucleotide polymorphism (SNP) markers from LG14 were used to saturate the R2 region. Two SNP markers, NSA_002316 and SFW01272, flanked R2 at a genetic distance of 2.8 and 1.8 cM, respectively. Of the three closely linked markers, SFW00211 amplified an allele specific for the presence of R2 in a marker validation set of 46 breeding lines, and SFW01272 was also shown to be diagnostic for R2. These newly developed markers, together with the previously identified markers linked to the gene R13a, were used to screen 524 F2 individuals from a cross of a confection R2 line and HA-R6 carrying R13a. Eleven homozygous double-resistant F2 plants with the gene combination of R2 and R13a were obtained. This double-resistant line will be extremely useful in confection sunflower, where few rust R-genes are available, risking a potential disease epidemic from the use of single gene resistance.

Technical Abstract: Rust (caused by Puccinia helianthi Schwein.) is a major disease of sunflower worldwide. Due to the frequent evolution of new pathogen races, the disease is a recurring threat to sunflower production especially in North America, Argentina, and Australia. The inbred line MC29 carries the rust resistance gene, R2, conferring resistance to numerous races of the rust fungus in the U.S., Canada, and Australia, and can be used as a broad-spectrum resistance resource. Based on phenotypic assessments and simple sequence repeat (SSR) analyses on the 117 F2 individuals derived from a cross of HA 89 with MC29 (USDA), R2 was mapped to linkage group (LG) 14 of the sunflower genome, and not to the previously reported location on LG9. The closest SSR marker HT567 was located at 4.3 cM distal to R2. Furthermore, 36 selected single nucleotide polymorphism (SNP) markers from LG14 were used to saturate the R2 region. Two SNP markers, NSA_002316 and SFW01272, flanked R2 at a genetic distance of 2.8 and 1.8 cM, respectively, delimiting R2 to an interval of 4.6 cM. Of the three closely linked markers, SFW00211 amplified an allele specific for the presence of R2 in a marker validation set of 46 breeding lines, and SFW01272 was also shown to be diagnostic for R2. These newly developed markers, together with the previously identified markers linked to the gene R13a, were used to screen 524 F2 individuals from a cross of a confection R2 line and HA-R6 carrying R13a. Eleven homozygous double-resistant F2 plants with the gene combination of R2 and R13a were obtained. This double-resistant line will be extremely useful in confection sunflower, where few rust R-genes are available and when R-genes are utilized they are typically incorporated singly, risking evolution of new virulence phenotypes and further disease epidemics.