Influence of seed colour on seed vigour in Brassica napus

Yellow seed colour in Brassica napus is a desired trait and has a strong impact on the quality of Canola and the processed products from the seed. The trait is accompanied with a thinner seed coat when compared to black seeds. For the model plant Arabidopsis thaliana, different mutants have been characterised showing the transparent testa phenotype to be associated with light seed colour due to the lack of anthocyanins. Regarding dormancy, viability and germination, the function of the seed coat has been investigated based on Arabidopsis mutants affected in seed pigmentation and/or testa structure (Debeaujon et al. 2000, Plant Physiol. 122, 403-413). In rapeseed (B. napus) the same effects are of interest, as in breeding nurseries reduced field emergence of yellow-seeded genotypes has often been observed. In relation to reduced thickness of the seed coat and altered pigmentation, this effect of impaired seed vigour may be explained differently: 1) reduction of resistance against mechanical injury caused by threshing and seed processing, 2) decrease of resistance against fungal pathogens due to seed injury, breakage and altered pigmentation, 3) increase of sensitivity against agrochemicals, 4) alteration in secondary plant metabolism, e.g. flavonoids, 5) reduced seed-coat related dormancy.