STEREOSPECIFIC ANALYSES OF SEED TRIACYLGLYCEROLS FROM HIGH-ERUCIC ACID BRASSICACEAE - DETECTION OF ERUCIC-ACID AT THE SN-2 POSITION IN BRASSICA-OLERACEA L GENOTYPES

Stereospecific analyses of triacylglycerols from selected high erucic acid breeding lines or cultivars of Brassica napus L. and B. oleracea L. have been performed. Initial lipase screening revealed that while all B. napus lines contained little or no erucic acid at the sn-2 position, several of the B. oleracea lines had significant proportions of erucic acid at this position. Detailed stereospecific analyses were performed on the triacylglycerols from these lines by using a Grignard-based deacylation, conversion of the sn-1, sn-2 and sn-3 monoacylglycerols to their di-dinitrophenyl methane (DNPU) derivatives, resolution of the di-DNPU-monoacylglycerols (MAGs) by high-performance liquid chromatography on a chiral column, transmethylation of each sn-di DNPU MAG fraction and analysis of the resulting fatty acid methyl esters by gas chromatography. The findings unequivocally demonstrate for the first time that, within the Brassicaceae, there exists B. oleracea germplasm containing seed oils with substantial erucic acid (30-35 mol%) at the sn-2 position. This has important implications for biotechnology and breeding efforts designed to increase the levels of erucic acid in rapeseed beyond 66 mol% to supply strategic industrial feedstocks. In the first instance, the germplasm will be of direct use in retrieving a gene encoding a Brassica lyso-phosphatidic acid acyltransferase with an affinity for erucoyl-CoA. In a breeding program, the germplasm offers promise for the introduction of this trait into B. napus by interspecific hybridization and embryo rescue.