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United States Department of Agriculture

Agricultural Research Service

Research Project: SUNFLOWER GERMPLASM DIVERSIFICATION AND CHARACTERIZATION UTILIZING WILD SUNFLOWER SPECIES, CYTOGENETICS, AND APPLIED GENOMICS

Location: Sunflower Research

Title: Genetic mapping of rust resistance genes in confection sunflower line HA-R6 and oilseed line RHA 397

Authors
item Gong, Li -
item Gulya, Thomas
item Markell, Sam -
item Hulke, Brent
item Qi, Lili

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 8, 2013
Publication Date: August 1, 2013
Citation: Gong, L., Gulya, T.J., Markell, S.G., Hulke, B.S., Qi, L.L. 2013. Genetic mapping of rust resistance genes in confection sunflower line HA-R6 and oilseed line RHA 397. Theoretical and Applied Genetics. 126(8):2039-2049.

Interpretive Summary: Sunflower (Helianthus annuus L.) is widely grown in the world, predominantly as an oilseed crop with some germplasm selected as confection types, intended for direct human consumption. Sunflower rust is one of the major yield limiting factors in sunflower production. Sunflowers with severe rust infection can have a significantly reduced yield. Additionally, the quality of the confection seeds infected by rust may not meet grading standards established by the industry and desired by consumers. Developing genetically resistant hybrids is the preferred approach for disease management. However, few widely effective resistance sources to sunflower rust have been identified in confection sunflower. The USDA inbred line HA-R6 is one of the few confection sunflower lines resistant to rust. A previous allelism test indicated that rust resistance genes in HA-R6 and RHA 397, an oilseed-type restorer line, are either allelic or closely linked; however, neither have been characterized nor genetically mapped. The objectives of this study are 1) to molecularly map the rust genes in HA-R6 and RHA 397, 2) to develop closely linked molecular markers for rust resistance diagnostics, and 3) to determine the resistance spectrum of two lines compared with other rust resistant lines. Two populations of 140 F2:3 families each from the crosses of HA 89, as susceptible parent, with HA-R6 and RHA 397 were inoculated with rust race 336 in the greenhouse. The rust resistance gene in the confection sunflower line HA-R6 was mapped to linkage group (LG) 13, flanked by the same molecular markers at the same position as the rust resistance gene in the oilseed sunflower line RHA 397, and thus, these two genes were designated as R13a and R13b, respectively. The DNA markers RGC15/16 and a newly developed marker SUN14 narrowed down the region flanking R13a and R13b into 4.9 cM and 0.1 cM, respectively. Both R13a and R13b are highly effective against all rust races tested so far. Our newly developed molecular markers will facilitate breeding efforts to pyramid the R13 genes with other rust R-genes and accelerate the development of rust-resistant sunflower hybrids in both confection and oilseed sunflowers.

Technical Abstract: Few widely effective resistance sources to sunflower rust, incited by Puccinia helianthi Schwein., have been identified in confection sunflower (Helianthus annuus L.). The USDA inbred line HA-R6 is one of the few confection sunflower lines resistant to rust. A previous allelism test indicated that rust resistance genes in HA-R6 and RHA 397, an oilseed-type restorer line, are either allelic or closely linked; however, neither have been characterized nor genetically mapped. The objectives of this study are 1) to molecularly map the rust resistance genes in HA-R6 and RHA 397, 2) to develop closely linked molecular markers for rust resistance diagnostics, and 3) to determine the resistance spectrum of two lines compared with other rust resistant lines. Two populations of 140 F2:3 families each from the crosses of HA 89, as susceptible parent, with HA-R6 and RHA 397 were inoculated with race 336 of P. helianthi in the greenhouse. The resistance genes (R-genes) in HA-R6 and RHA 397 were genetically mapped to the lower end of linkage group 13, which encompasses a large R-gene cluster, and were designated as R13a and R13b, respectively. In the initial maps, SSR (simple sequence repeat) and InDel (insertion and deletion) markers revealed 7.6 and 9.4 cM flanking regions for R13a and R13b, respectively, linked with a common marker set of four co-segregating markers, ORS191, ORS316, ORS581, and ZVG61, in the distal side and one marker ORS464 in the proximal side. To identify new markers closer to the genes, sunflower RGC (resistance gene candidate) markers linked to the downy mildew R-gene Pl8 and located at the same region as R13a and R13b were selected to screen the two F2 populations. The RGC markers RGC15/16 and a newly developed marker SUN14 designed from a BAC contig anchored by RGC251 further narrowed down the region flanking R13a and R13b to 4.9 cM and 0.1 cM, respectively. Both R13a and R13b are highly effective against all rust races tested so far. Our newly developed molecular markers will facilitate breeding efforts to pyramid the R13 genes with other rust R-genes and accelerate the development of rust-resistant sunflower hybrids in both confection and oilseed sunflowers.

Last Modified: 10/1/2014
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