Biochemical and molecular analyses of flavonoid metabolism in Brassica napus seed: identification of key factors for seed coat pigmentation

Introduction Oilseed rape is a worldwide major oil crop that also supplies oil-free meal with high protein content (38-40%) and well-balanced amino acid composition. Currently, the quality of oilseed rape meal is still altered by secondary metabolites such as procyanidins. These compounds are flavonoid end-products that accumulate specifically in the seed coat during seed embryogenesis and maturation as colorless polymers that turn to brown-to-dark upon oxidations during seed desiccation (Nesi et al., 2009). Despite their biological effects in seed sheltering, they are considered as anti-nutritionals since they impact negatively on animal production (especially for non-ruminant livestock) by altering feed intake and/or by lowering live weight gains. Yellow seediness, which is thought to be associated with a reduction of procyanidin content, represents a major agronomic trait for Brassica crop improvement and has concentrated important research efforts over the last two decades. Indeed, the yellow-seed trait is linked to increased seed oil content and lower dietary fibre content associated with a thinner seed coat (Simbaya et al., 1995; Slominski et al., 1999). Therefore, the resulting meal has an improved energy value. Such yellowseeded lines naturally exist for several Brassica spp., but not for B. napus. Breeding of B. napus yellow-seeded lines through interspecific crosses often results in unstable lines with poor agronomic properties. Therefore, development of yellow-seeded lines requires better knowledge of the seed flavonoid pathway in blackand yellow-seeded B. napus lines. The present work aimed to identify the biochemical determinants linked to the yellow color of B. napus seed coat.