Page Banner

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: Molecular tagging of a novel rust resistance gene R12 in sunflower (Helianthus annuus L.)

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

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 31, 2012
Publication Date: January 7, 2013
Citation: Gong, L., Hulke, B.S., Gulya Jr, T.J., Markell, S.G., Qi, L.L. 2013. Molecular tagging of a novel rust resistance gene R12 in sunflower (Helianthus annuus L.). Theoretical and Applied Genetics. 126(1):93-99.

Interpretive Summary: Sunflower rust incited by Puccinia helianthi Schwein. emerged as one of the most serious diseases in sunflower planting area of North America in the past few years as a result of increasing incidence and lack of resistance to new rust races. Prior to 2008, rust usually appeared during the late reproductive stages of sunflower development and rarely resulted in economic damage. However, earlier infestation of rust (prior to the bloom stage) was observed in 2008, and consequently created a greater yield loss. Cultivation of sunflower resistant hybrids is the best alternative for disease control due to the factors such as cost savings, reduced labor, and no negative environmental impact. RHA 464, a newly released sunflower male fertility restorer line, was resistant to both of the predominant rust race 336 and the most virulent race 777. The gene conditioning rust resistance in RHA 464 was introgressed from wild Helianthus annuus. The objectives of this study are to identify molecular markers linked to the rust resistance gene and to investigate the relationship of that gene with the rust R-genes present in HA-R6, HA-R8 and RHA 397, all of which were also resistant to rust races 336 and 777. Seedling rust response scores for F2 population and F2:3 families indicated that a single dominant gene confers rust resistance in RHA 464, and this gene was designated as R12. We used a technique called bulk segregant analysis to locate this gene in the sunflower linkage group 11. In subsequent genetic mapping, we discovered a co-dominant marker CRT275-11 linked to R12 in a genetic distance of 1.0 cM and a dominant marker ZVG53 flanked to R12 in a genetic distance of 9.6 cM. The allelism test demonstrated that R12 is not allelic to the rust genes in HA-R6, HA-R8 and RHA 397, and it is also not linked to any previously mapped rust genes. Discovery of the R12 novel rust resistance locus in sunflower and associated markers will potentially support the molecular marker assisted introgression and pyramiding of R12 into sunflower breeding lines.

Technical Abstract: Sunflower production in North America has recently suffered economic losses in yield and seed quality from sunflower rust (Puccinia helianthi Schwein.) because of the increasing incidence and lack of resistance to new rust races. RHA 464, a newly released sunflower male fertility restorer line, is resistant to both of the predominant rust race 336 and the most virulent race 777. The gene conditioning rust resistance in RHA 464 originates from wild Helianthus annuus, however, it has not been molecularly marked and the independence of this gene from other rust loci has not yet been examined. The objectives of this study are to identify molecular markers linked to this rust resistance gene and to investigate the allelism of that gene with the rust resistance genes present in HA-R6, HA-R8 and RHA 397, all of which are also resistant to rust races 336 and 777. Seedling rust response scores for F2 population and F2:3 families indicated that a single dominant gene confers rust resistance in RHA 464, and this gene was designated as R12. Bulked segregant analysis identified 10 markers polymorphic between resistant- and susceptible- bulks. In subsequent genetic mapping, the ten markers covered 33.4 cM of genetic distance in LG11. A co-dominant marker CRT275-11 is the closest marker distal to R12 with a genetic distance of 1.0 cM, while ZVG53, a dominant marker linked in the repulsion phase, is proximal to R12 with a genetic distance of 9.6 cM. The allelism test demonstrated that R12 is not allelic to the rust genes in HA-R6, HA-R8 and RHA 397, and it is also not linked to any previously mapped rust genes. Discovery of the R12 novel rust resistance locus in sunflower and associated markers will potentially support the molecular marker assisted introgression and pyramiding of R12 into sunflower breeding lines.

Last Modified: 7/22/2014