Cultivated meadowfoam (Limnanthes alba Benth.) is an annual oil seed crop native to southern Oregon. California and British Columbia. The genus Limnanthes is composed of nine species and divided into two sections, Inflexae and Reflexae. The seed oil of meadowfoam is a rich source of erucic acid and several novel very long-chain fatty acids (VLCs). The former has been linked to increased risk of heart disease. The safe limit of erucic acid for human consumption is up to 5% of total fatty acids. Because the erucic acid concentrations of wildtype lines typically range from 9 to 23% and low erucic acid variants have not been discovered, chemical mutagenesis was used to develop a mutant line (LE76) with greatly reduced erucic acid (3%). The phenotypic distributions of F��� progeny from crosses between wildtype and mutant lines were continuous and differed across genetic backgrounds. Quantitative trait loci (QTL) affecting erucic and dienoic acid were mapped using F���:��� progeny from a cross between LE76 and Wheeler (a wildtype line) and a simple sequence repeat (SSR) map spanning the meadowfoam genome. The domestication of meadowfoam was based on L. alba, belonging to section Inflexac. The secondary and tertiary gene pools have not been important to the domestication process and have not supplied diversity for meadowfoam breeding. With the objectives of introgressing genes from wild relatives and also producing cytoplasmic male sterile lines by inserting the nuclear genome of L. alba into wild cytoplasm, inter-sectional crosses involving L. alba and three subspecies of L. douglasii and intra-sectional crosses involving L. alba and two subspecies of L. floccosa were carried out. The isolation mechanisms involved in keeping species apart from each other were found to be different within and between sections. The study of partially fertile intra-sectional hybrids showed that the reduced pollen viability (30-33%) was not due to structural differences between the chromosomes of the two species, as normal meiotic behavior was observed in PMCs. The inter-sectional crosses were found to be incompatible and various abnormalities during pollen tube growth were observed. / Graduation date: 2002

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 (C������ and C������) 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 peta1 area (pa), seeds per plant (spp) and seeds per flower (spf)I 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". / Graduation date: 2002