Secondary seed dormancy in oilseed rape is a phenomenon that allows seeds to survive in the soil for many years without germination. Following soil cultivation, dormant seeds may germinate in subsequent years, and they are the main reason for the occurrence of volunteer oilseed rape plants in successive crops. Inheritance of secondary dormancy may be related to seed longevity (SL) in the soil. Genetic reduction in secondary dormancy and SL could provide a mean to reduce the frequency of volunteer plants and especially the dispersal of transgenic oilseed rape. The aim of the present study was to analyse secondary dormancy, germination rate and SL of 28 black‐seeded winter oilseed rape cultivars using in vitro laboratory tests. The material was tested in field experiments at six different locations in Germany in 2008/2009. Significant effects of the genotype and the location on all traits were found. Heritability was high for secondary dormancy (0.97) and moderate for germination rate (0.70) and SL (0.71). Results indicate that a selection for low secondary dormancy would be effective.

Abstract. Light leaf spot, caused by Pyrenopeziza brassicae, is the most damaging disease problem in oilseed rape (Brassica napus) in the United Kingdom. According to recent survey data, the severity of epidemics has increased progressively across the UK, with yield losses of up to £160M per annum in England and more severe epidemics in Scotland. Light leaf spot is a polycyclic disease, with primary inoculum consisting of airborne ascospores produced on diseased debris from the previous cropping season. Splash-dispersed conidia produced on diseased leaves are the main component of the secondary inoculum. Pyrenopeziza brassicae is also able to infect and cause considerable yield losses on vegetable brassicas, especially Brussels sprouts. There may be spread of light leaf spot among different Brassica species. Since they have a wide host range and frequent occurrence of sexual reproduction, P. brassicae populations are likely to have considerable genetic diversity, and evidence suggests population variations between different geographic regions, which need further study. Available disease-management tools are not sufficient to provide adequate control of the disease. There is a need to identify new sources of resistance, which can be integrated with fungicide applications to achieve sustainable management of light leaf spot. Several major resistance genes and quantitative trait loci have been identified in previous studies, but rapid improvements in the understanding of molecular mechanisms underpinning B. napus-P. brassicae interactions can be expected through exploitation of novel genetic and genomic information for brassicas and extracellular fungal pathogens.