Submitted to: Plant Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/27/2006
Publication Date: 3/1/2007
Citation: Jan, C.C., Vick, B.A. 2007. Inheritance and allelic relationships of fertility restoration genes for seven new sources of male-sterile cytoplasm in sunflower. Plant Breeding. 126:213-217. Interpretive Summary: The use of a single cytoplasm male-sterile (cms) cms PET1 cytoplasm and the Rf1 fertility restoration gene for hybrid sunflower production since the early 1970s makes the crop genetically vulnerable. One reason for not having other cms-fertility restoration systems is the inability to find stable and complete cms sources and corresponding strong fertility restoration genes. Of the 70 sunflower cms sources, only 19 have been reported to have Rf genes and are supported with inheritance studies. This report characterized six selected mutant cms HA 89 lines in the cytoplasmic background of H. annuus resulted from induced mutation, and cms PI 432513 discovered in wild H. annuus. Inheritance study indicated these new cms sources are restored by the same single dominant gene, Rf1, used in all commercial sunflower hybrids, and the four new restoration genes identified are alleles of the classical Rf1 gene. These new cytoplasmic male-sterility sources have no adverse effect on plant performance, and will be preferred alternatives to the presently used cms PET1 because of the already available commercial restoration lines with Rf1 gene.
Technical Abstract: The inheritance of fertility restoration of six mitomycin C and streptomycin induced cytoplasmic male-sterile (cms) mutants and one cms line derived from Native American cultivar PI 432513 was evaluated. These cms sources were also compared with the commercially used cms PET1 (Helianthus petiolaris Nutt.) cytoplasm, using USDA inbred lines with restoration genes (Rf1) specific for cms PET1 and new restoration lines identified for cms PI 432513. Restoration genes for cms PI 432513 were found in 'Armavir', 'VNIIMK', 'P21', and male-fertile plants of PI 432513. F2 segregation ratios of crosses between cms PI 432513 and these restoration sources indicated a single dominant gene controlled fertility restoration. Progenies of cms PI 432513 testcrossed with F1's of half-diallel crosses among the respective four homozygous restoration lines and RHA 274 suggested that the restoration genes of RHA 274, VNIIMK, P21, and PI 432513 were at the same locus. Restoration genes from VNIIMK, P21, and PI 432513 satisfactorily restored pollen stainability in the heterozygous condition. Fertility restoration capability of these genes for the six mutant cms HA 89 and cms HA 89 (in PET1 cytoplasm) was observed. The mutant cms HA 89 lines were restored completely by RHA 266, RHA 274, RHA 280, and RHA 296, and F2's segregation ratios indicated single dominant gene control, implying a common cytoplasmic male sterility similarity in all lines. F1's of half-diallel crosses among RHA 266, RHA 273, RHA 274, RHA 280, and RHA 296 were testcrossed onto the cms lines, and their all male-fertile progenies among lines, except RHA 280, confirmed the single Rf1 gene locus for fertility restoration. The restoration gene in confection line RHA 280 was at a different locus than Rf1 and is equally capable of restoring all the lines. Cms HA 89 mutants and cms PI 432513 are in a H. annuus cytoplasm and are less likely to have adverse interaction with the nuclear genes of cultivated sunflower than the cms PET1, and will provide immediate alternative cms sources for reducing the genetic vulnerability resulting from the exclusive use of a single cms source in sunflower (H. annuus) hybrid production.