Mapping quantitative trait loci underlying genome-wide recombination rate and mating system differences in meadowfoam

Meadowfoam (Limnanthes alba Bentham; Order: Brassicales; Family: Limnanthaceae) is a self-compatible, predominantly allogamous, insect pollinated species. Meadowfoam oil is a source of novel unsaturated very-long-chain (VLC) seed oils (C₂₀ and C₂₂) with low concentrations of saturated fatty acids (typically less than 2%) and outstanding oxidative stability. Here we report the development of 389 SSR markers for meadowfoam. All the 389 SSRs were screened on 14 meadowfoam germplasm accessions to assess their utility and efficiency. Ninety-six percent of the SSR markers (373 out of 389) were polymorphic among the 14-germplasm accessions (from nine taxa) with a mean heterozygosity of 0.63.; We also report that the physical size of the meadowfoam genome was estimated to be 5.52 pg using flow cytometry; thus, the meadowfoam genome is ca. 16 times larger than the Arabidopsis genome. Karyotype analyses revealed that the meadowfoam genome is made up of two metacentric and three submetacentric chromosomes. Meadowfoam has two pairs of chromosomes with subterminal nucleolar organizing regions (NOR's). A genetic map comprised of 84 SSR loci dispersed among five linkage groups with 11 to 22 SSR loci per linkage (6 SSR loci segregated independently) was constructed. The map was 988.7 cM long with a mean density of 11.8 cM and minimal clustering of loci.; A total of 20 quantitative trait loci (QTL) were identified for five mating system characters in meadowfoam, using the SSR linkage map of meadowfoam. Individual QTL for mating system traits [petal area (pa), seeds per plant (spp) and seeds per flower (spf)] account for up to 20% of the backcross phenotypic variance, with most traits showing QTL effects of 5–15%. The QTL for protandry and chiasma frequency were adjacent to the QTL for spp and spf. This study has provided evidence that the correlation between the chiasma frequency and the type of mating system is not a direct developmental relationship between these factors, but is due to a selective advantage of the combination of the characters found. The speculation that the genetic factors underlying chiasma frequency and autonomous seed set have co-evolved during evolution negates the self-fertilization as an “evolutionary dead end”.