Construction of a genetic map and localization of major traits in sunflower, Helianthus annuus L

Abstract

We developed a segregating mapping population from the cross RHA325(cms) × HA342 comprising 183 F2 individuals. RHA325 is an open American inbred line based on the PET1 cytoplasm, while HA342 is a maintainer line for this cytoplasm. The F2 and derived populations segregate for male fertility vs. sterility, downy mildew (Plasmopara halstedii) resistance (Pl2) vs. susceptibility and oleic vs. linoleic acid content. A genetic map was developed covering 1751.5 cM with 202 AFLP and 19 SSR markers in 18 linkage groups. Thirteen linkage groups contain one or more SSR markers and are numbered according to Tang et al. see Theoretical and Applied Genetics (2002) 105, 1124-1136]. A segregation ratio of 1 (male fertile, Rf1Rf1):2 (male fertile, Rf1rf1):1 (male sterile, rf1rf1) was observed in the F2 population as expected for one segregating restorer gene (χ2=2.83, P=0.24). In F3, 14 progeny plants of each fertile F2 individual were evaluated for male fertility to distinguish between F2 plants being homozygous or heterozygous for the restorer gene. The data obtained from the F3 progenies were confirmed by segregation analyses in an F2BC1 population. The Rf1 locus was shown to be located on linkage group 13, containing the SSR markers ORS388 and ORS1030. Using a whole-seedling-immersion test by Gulya et al. see Helia (1991) 14, 11-20] applied to F3 progeny plants, we found that the F2 population RHA325(cms) × HA342 segregated for P. halstedii reaction at a ratio of 1 (Pl2Pl2):2 (Pl2pl2):1 (pl2pl2); χ2=0.83 (P=0.65). The Pl2 gene was demonstrated to be located on linkage group 8 together with the SSR marker ORS599. Furthermore, quantitative trait loci for oleic vs. linoleic acid contents (LOD>3) could be localized on linkage group A. Future work will concentrate on marker saturation of the genetic map.