Florin Daniel Lipsa, R. J. Snowdon, W. Friedt
Oilseed rape/canola (Brassica napus) represents a potentially valuable source of vegetable protein due to its favourable composition of essential amino acids. However, the use of rapeseed protein for human nutrition is presently not possible due to the presence of major anti-nutritive compounds, which also reduce the value of rapeseed meal as a source of animal feed. Especially relevant in this regard are dietary fibre, dark-coloured tannins and bitter-tasting sinapate esters. Yellow coloured seeds are of particular interest for oilseed rape breeding because of their association with a thinner seed coat resulting in reduced dietary fibre and condensed tannin content. This considerably improves the feed and protein quality of rapeseed meal after oil extraction. Plant tannins make up a distinctive group of high molecular weight phenolic compounds that have the ability to complex strongly with proteins, starch, cellulose and minerals. Chemically three groups of tannins are distinguishable: phlorotannins, hydrolysable and condensed tannins (syn. proanthocyanidins, PAs). In rapeseed (Brassica napus L.) condensed tannins are largely responsible for the dark colour of the seed coat, where they accumulate predominantly in the endothelium cell layer between the outer integument and the aleuronic layer. Whereas the proportion of condensed tannins in the cotyledons of B. napus seeds is comparatively low (0.1-0.5% of dry weight), condensed tannins in dark-seeded B. napus can comprise up to 6% of the seed coat. The objective of this study was to identify quantitative trait loci (QTL) for seed colour, individual and total condensed tannins (syn. proanthocyanidine, PAs) content in a winter rapeseed doubled haploid (DH) population. The plant material consisted of 166 DH lines derived from a cross between an inbred line of the black-seeded German winter oilseed rape cultivar ‘Express’ and the true-breeding, yellow-seeded line ‘1012/98’, both with 00-seed quality. The QTL were mapped using the software PLABQTL based on seed analyses of DH lines grown on field trials in Rauischholzhausen and Gross-Gerau (Germany). Seed colour was measured quantitatively based on digital reflectance values. Individual PAs and total flavonoid content were quantified via HPLC (High Performance Liquid Chromatography) using internal standards for quantification.
Brassica napus; seed colour; condensed tannins; QTL mapping
Presentation: oral