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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 Title: Genetics and mapping of the R11 gene conferring resistance to recently emerged rust races, tightly linked to male fertility restoration, in sunflower (Helianthus annuus L.)

Authors
item Qi, Lili
item Seiler, Gerald
item Vick, Brady
item Gulya Jr, Thomas

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 4, 2012
Publication Date: August 15, 2012
Citation: Qi, L.L., Seiler, G.J., Vick, B.A., Gulya, T.J. 2012. Genetics and mapping of the R11 gene conferring resistance to recently emerged rust races, tightly linked to male fertility restoration, in sunflower (Helianthus annuus L.). Theoretical and Applied Genetics. 125:921-932.

Interpretive Summary: Sunflower oil provides about 13% of the world’s edible oil. The high proportion of polyunsaturated fatty acids renders sunflower oil as a popular source of essential fatty acids in the diet. As the second largest hybrid crop in the world, hybrid sunflowers contribute to a 20% yield advantage over the open-pollinated varieties. However, sunflower production in North America has recently been threatened by the development of new virulent races of sunflower rust. The majority of commercial hybrids are susceptible to the new predominant and virulent races. A male-sterile restorer line, Rf ANN-1742, was identified as resistant to the newly emerged rust races. The aim of this study was to elucidate the inheritance of rust resistance and fertility restoration and identify the chromosome location of the underlying genes in Rf ANN-1742. Statistical analysis of the segregation of rust response and fertility in F2 and F3 populations revealed that both traits are controlled by single dominant genes derived from alien segments of Rf ANN-1742, and that the rust resistance gene is closely linked to the restorer gene. The two genes were designated as R11 and Rf5, respectively. A set of 723 simple sequence repeat (SSR) DNA markers of sunflower was used to identify polymorphic markers (markers that are different) between HA 89 and the resistant plant. We used the polymorphic markers together with a technique called bulk segregant analysis to map the two genes to linkage groups (LGs). Based on the SSR analyses of 192 F2 individuals, R11 and Rf5 both mapped to the lower end of LG 13 at a close genetic distance of 1.6 cM. The two shared a common marker, ORS728, which was mapped 1.3 cM proximal to Rf5 and 0.3 cM distal to R11 (Rf5/ORS728/R11). Two additional SSRs were linked to Rf5 and R11: ORS995 was 4.8 cM distal to Rf5 and ORS45 was 1.1 cM proximal to R11. The advantage of such an introduced alien segment harboring two genes is its large phenotypic effect and simple inheritance thereby facilitating their rapid deployment in sunflower breeding programs. R11 is genetically independent from the rust R-genes R1, R2, and R5, but may be closely linked to the rust R-gene Radv derived from wild H. argophyllus, forming a large rust R-gene cluster of Radv/R11/ R4 in the lower end of LG 13. Any combination of the genes R2, R4, and R5 with R11 would give resistance to a majority of rust races and provide protection against the spread of new rust races. The molecular markers closely linked to the different resistance genes should make this task more feasible, and will allow breeders to effectively select disease-resistant progeny in early segregating generations.

Technical Abstract: Sunflower oil is one of the major sources of edible oil. As the second largest hybrid crop in the world, hybrid sunflowers are developed by using the PET1 cytoplasmic male sterility system that contributes a 20% yield advantage over the open-pollinated varieties. However, sunflower production in North America has recently been threatened by the evolution of new virulent pathotypes of sunflower rust caused by the fungus Puccinia helianthi Schwein. Rf ANN-1742, an ‘HA 89’ backcross restorer line derived from wild annual sunflower (Helianthus annuus L), was identified as resistant to the newly emerged rust races. The aim of this study was to elucidate the inheritance of rust resistance and fertility restoration and identify the chromosome location of the underlining genes in Rf ANN-1742. Chi-squared analysis of the segregation of rust response and fertility in F2 and F3 populations revealed that both traits are controlled by single dominant genes, and that the rust resistance gene is closely linked to the restorer gene in the coupling phase. The two genes were designated as R11 and Rf5, respectively. A set of 723 mapped SSR markers of sunflower was used to screen the polymorphism between HA 89 and the resistant plant. Bulked segregant analysis subsequently located R11 on linkage group (LG) 13 of sunflower. Based on the SSR analyses of 192 F2 individuals, R11 and Rf5 both mapped to the lower end of LG 13 at a genetic distance of 1.6 cM, and shared a common marker ORS728 which was mapped 1.3 cM proximal to Rf5 and 0.3 cM distal to R11 (Rf5/ORS728/R11). Two additional SSRs were linked to Rf5 and R11: ORS995 was 4.8 cM distal to Rf5 and ORS45 was 1.1 cM proximal to R11. The advantage of such an introduced alien segment harboring two genes is its large phenotypic effect and simple inheritance thereby facilitating their rapid deployment in sunflower breeding programs. Suppressed recombination was observed in LGs 2, 9, and 11 as it was evident that no recombination occurred in the introgressed regions of LGs 2 (~ 20 cM), 9 (~ 38 cM), and 11 (~ 60 cM), respectively. R11 is genetically independent from the rust R-genes R1, R2, and R5, but may be closely linked to the rust R-gene Radv derived from wild H. argophyllus, forming a large rust R-gene cluster of Radv/R11/ R4 in the lower end of LG 13. The relationship of Rf5 with Rf1 is discussed based on marker association analysis.

Last Modified: 11/23/2014
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