Quantitative genetic analysis of condensed tannins in oilseed rape meal

Condensed tannins (proanthocyanidins, PAs) in the seed meal of oilseed rape can potentially have a negative impact on non-ruminant livestock nutrition, particularly because of their ability to form indigestible, astringent or bitter-tasting complexes with proteins. One option to overcome this problem is the breeding of oilseed rape varieties with reduced condensed tannins in the seed coat. This might be achievable via selection of genotypes with thinner seed coats and consequently reduced condensed tannin accumulation (seed coat structural cell mutants), or alternatively by selection of genotypes with reduced biosynthesis of condensed tannins (flavonoid biosynthesis mutants). Both types of transparent testa (TT) mutants are well-characterised in Arabidopsis; however the genetic basis of the yellow-seed trait in the polyploid genome of rapeseed is still not completely understood. In this study, genetic and chemical analyses of PAs were performed in 166 doubled haploid (DH) rapeseed lines from the segregating Brassica napus doubled haploid population YE2-DH(black seed 9 yellow seed). Using these analyses, the relationship between seed colour and PA fractions in B. napus was investigated with a view to improving the rapeseed meal quality. Proanthocyanidin contents were estimated by vanillin and HPLC assays and the obtained values were used to identify quantitative trait loci. Closely linked molecular markers that were identified during this study for the target traits (seed colour, condensed tannins) can be valuable tools for breeding of new oilseed rape cultivars with reduced levels of antinutritive PA compounds.