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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: Diversifying sunflower germplasm by integration and mapping of a novel male fertility restoration gene

Authors
item Liu, Zhao -
item Wang, Dexing -
item Feng, Jiuhuan -
item SEILER, GERALD
item Cai, Xiwen -
item JAN, CHAO-CHIEN

Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 22, 2012
Publication Date: March 1, 2013
Citation: Liu, Z., Wang, D., Feng, J., Seiler, G.J., Cai, X., Jan, C. 2013. Diversifying sunflower germplasm by integration and mapping of a novel male fertility restoration gene. Genetics. 193:727-737.

Interpretive Summary: Cytoplasmic male sterility (CMS) is caused by aberrant mitochondrial genes that prevent pollen development. Nuclear fertility restoration (Rf) genes in fertility restorer lines compensate the CMS gene effects and thus produce a male-fertile phenotype. The combination of CMS PET-1, originating from wild Helianthus petiolaris subsp. petiolaris Nutt., and the corresponding Rf1 gene, has been exclusively used for commercial sunflower hybrid seed production since the early 1970s. A new CMS line 514A was developed recently with H. tuberosus cytoplasm. Thirty-three maintainers and restorers for CMS PET-1 and 20 additional tester lines, failed to restore its fertility. In this study, five interspecific amphiloids and a hexaploid H. californicus accession were used for further screening for its Rf gene. We report the detection of the Rf gene in one amphiploid (Amp H. angustifolius/P 21, 2n=68), and its characterization and molecular mapping. Crossing and backcrossing were conducted in order to integrate the Rf gene into cultivated sunflower. Genetic analysis of three male-fertile plants (2n=35) suggested that this gene, designated as Rf6, was located on one alien chromosome. Genomic in situ hybridization (GISH) analysis in 23 F2 plants suggested the Rf6 gene located on a chromosome with a translocation on the long arm. The Rf6 gene was mapped on LG 3 of the public sunflower SSR map, with eight markers linked to it, covering a genetic distance of 17.3 and 10.8 cM in the two mapping populations, respectively. The closest markers to it were ORS13 and ORS1114, at a distance of 1.6 cM. Severe deviations were detected for both the fertility trait and the linked marker loci, suggesting recombination suppression or gamete selection in this region. The results provide a new alternative CMS/Rf gene system, which will expand the diversity of sunflower germplasms for breeding, and help to understand the interaction between the cytoplasm and nuclear genes. The materials developed within the process will be evaluated and released as germplasms in the next experiments.

Technical Abstract: The combination of a single cytoplasmic male-sterile (CMS) PET-1, originating from wild Helianthus petiolaris subsp. petiolaris Nutt., and the corresponding fertility restoration gene Rf1, has been used for commercial sunflower hybrid seed production worldwide since the early 1970s. A new CMS line 514A was developed recently with H. tuberosus cytoplasm. Thirty-three maintainers and restorers for CMS PET-1 and 20 additional tester lines, failed to restore its fertility. In this study, we report the detection of the Rf gene in one amphiploid (Amp H. angustifolius/P 21, 2n=68), and its characterization and molecular mapping. Crossing and backcrossing were conducted to incorporate the Rf gene into cultivated sunflower. Genetic analysis of three male-fertile plants (2n=35) suggested that this gene, designated as Rf6, was located on the single alien chromosome. Genomic in situ hybridization (GISH) analysis suggested the Rf6 gene located on a chromosome with a translocation on the long arm. The Rf6 gene was mapped on LG 3 of the public sunflower SSR map. Eight markers were linked to this gene, covering a genetic distance of 17.3 and 10.8 cM in the two mapping populations, respectively, with the closest markers ORS13 and ORS1114 at a distance of 1.6 cM. Severe deviations were detected for both the fertility trait and the linked marker loci, suggesting recombination suppression or gamete selection in this region. The results provide a new alternative CMS/Rf gene system, which will expand the diversity of sunflower germplasms for breeding, and help to understand the interaction between the cytoplasm and nuclear genes.

Last Modified: 9/29/2014
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