The identification and mapping of candidate genes and QTL involved in the fatty acid desaturation pathway in Brassica napus

Abstract

We constructed a linkage map for the population QDH, which was derived from a cross between an oilseed rape cultivar and a resynthesised Brassica napus. The linkage map included ten markers linked to loci orthologous to those encoding fatty acid biosynthesis genes in Arabidopsis thaliana. The QDH population contains a high level of allelic variation, particularly in the C genome. We conducted quantitative trait locus (QTL) analyses, using field data obtained over 3 years, for the fatty acid composition of seed oil. The population segregates for the two major loci controlling erucic acid content, on linkage groups A8 and C3, which quantitatively affect the content of other fatty acids and is a problem generally encountered when crossing "wild" germplasm with cultivated "double low" oilseed rape cultivars. We assessed three methods for QTL analysis, interval mapping, multiple QTL mapping and single marker regression analysis of the subset of lines with low erucic acid. We found the third of these methods to be most appropriate for our main purpose, which was the study of the genetic control of the desaturation of 18-carbon fatty acids. This method enabled us to decouple the effect of the segregation of the erucic acid-controlling loci and identify 34 QTL for fatty acid content of seed oil, 14 in the A genome and 20 in the C genome. The QTL indicate the presence of 13 loci with novel alleles inherited from the progenitors of the resynthesised B. napus that might be useful for modulating the content or extent of desaturation of polyunsaturated fatty acids, only one of which coincides with the anticipated position of a candidate gene, an orthologue of FAD2.

Seed Quality Traits Can Be Predicted with High Accuracy in Brassica napus Using Genomic Data

“…For instance, the major QTL located in A08 and C03 (Table 2) totally explained 76.66% of the phenotypic variance for erucic acid, which has been widely identified previously in TN DH population and other mapping populations of B . napus [21, 22, 24, 73]. The major QTL located on C03 and explaining 16.44% of the phenotypic variance for oil content was identified in both of TN DH population and KN DH population [74].…”

Quantitative trait loci (QTLs) analysis of palm oil fatty acid composition in an interspecific pseudo-backcross from Elaeis oleifera (H.B.K.) Cortés and oil palm (Elaeis guineensis Jacq.)

“…The phenotypic values of fatty acids in traces or in small amounts (C14:0, C16:1, C18:2, C18:3, C20:0, and C20:1) did not follow a normal distribution. The non-parametric Kruskal-Wallis (KW) test should be considered here as more accurate compared to the IM or MQM methods, as these latter are biased by deviations from normality (Smooker et al 2011).…”

“…The traits controlled by multiple genes such as palm oil composition can be deciphered using modern DNA marker technologies to implement a marker-assisted selection (MAS) for more desirable fatty acid composition, as it is already done for other oil crops like oilseed rape (Brassica napus) (Hu et al 1999(Hu et al , 2006Smooker et al 2011) soybean (Glycine max (L.) Merr.) (Wilson et al 2001;Monteros et al 2008;Ha et al 2010;Li et al 2011;Chen et al 2012) and olive (Olea europaea L.) (Poghosyan et al 1999;Hernández et al 2005;Banilas et al 2011).…”

Genome-Wide Association Study of Genetic Control of Seed Fatty Acid Biosynthesis in Brassica napus

“…Three of the major fatty acids (FAs) in oilseed rape oil are the monounsaturated FA oleic acid and the two polyunsaturated FAs linoleic acid and linolenic acid (Smooker et al, 2011). The high nutritional value of B. napus oil compared to other vegetable oils is attributed to a high level of oleic acid, as well as an optimal ratio (2:1) of the essential linoleic (omega 6) and linolenic (omega 3) FAs (Hu et al, 2006).…”