Genetics of low erucic acid and cytological analyses of wide hybrids in meadowfoam

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 F2 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 F2:3 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 Inflexae. 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.