Towards a Saturated Molecular Genetic Linkage Map for Cultivated Sunflower

The density and utility of the molecular genetic linkage map of cultivated sunflower (Helianthus annuus L.) has been greatly increased by the development and mapping of several hundred simple sequence repeat (SSR) markers. Of 1089 public SSR markers described thus far, 408 have been mapped in a recombinant inbred line (RIL) mapping population (RHA280 × RHA801). The goal of the present research was to increase the density of the sunflower map by constructing a new RIL map (PHA X PHB) based on SSRs, adding loci for newly developed SSR markers to the RHA280 × RHA801 RIL map, and integrating the restriction fragment length polymorphism (RFLP) and SSR maps of sunflower. The latter was accomplished by adding 120 SSR marker loci to a backbone of 80 RFLP marker loci on the HA370 x HA372 F 2 map. The map spanned 1275.4 centimorgans (cM) and had a mean density of 6.3 cM per locus. The PHA x PHB SSR map was constructed from 264 SSR marker loci, spanned 1199.4 cM, and had a mean density of 4.5 cM per locus. The RHA280 × RHA801 map was constructed by adding 118 new SSR and insertion-deletion (INDEL) marker loci to 459 previously mapped SSR marker loci. The 577-locus map spanned 1423.0 cM and had a mean density of 2.5 cM per locus. The three maps were constructed from 1044 DNA marker loci (701 unique SSR and 89 unique RFLP or INDEL marker loci) and supply a dense genome-wide framework of sequence-based DNA markers for molecular breeding and genomics research in sunflower.