Genetic Mapping of a Macromutation and Quantitative Trait Loci underlying Fatty Acid Composition Differences in Meadowfoam Oil

Abstract

The seed oil of meadowfoam (Limnanthes alba Hartw. ex Benth.) is a rich source of very long‐chain fatty acids (VLCs), primarily 20:1Δ5, 22:1Δ5, 22:1Δ13 (erucic acid), and 22:2Δ5Δ13 (dienoic acid). Wild‐type L alba ssp. versicolor populations produce more erucic and less dienoic acid than wild‐type L. alba ssp. alba populations, phenotypic differences that are caused by the macromutation E and possibly by quantitative trait loci (QTL). The aim of this study was to map the E locus and QTL affecting fatty acid concentrations among intersubspecific backcross progeny. The segregation ratio for the E locus (94 Ee to 86 ee progeny) was not significantly different from one to one (P = 0.84). The E locus was associated with 94 and 77% of the phenotypic variance for erucic and dienoic acid concentration, respectively. Erucic acid varied from 42 to 151 g kg−1 among Ee and 185 to 269 g kg−1 among ee progeny, while dienoic acid varied from 151 to 318 g kg−1 among Ee and 66 to 209 g kg−1 among ee progeny. The E locus mapped to Linkage Group 4 and pleiotropically affected every VLC. Composite interval mapping, performed with the E locus and 18 background markers as cofactors, was used to search the genome for QTL. Two significant QTL peaks were found for erucic and dienoic acid on Linkage Group 4. One QTL was centered on the E locus and produced a massive peak. The other QTL produced a marginally significant peak 30.4 cM downstream of the E locus and was associated with less than 1% of the phenotypic variance. The segregation of additional QTL in this population affecting dienoic acid cannot be ruled out.