Tocopherols are natural antioxidants found in all vegetable oils. They are important dietary nutrients and thus breeding for increased tocopherol content is a new and important objective in canola (Brassica napus L.). Tocopherols exist in four forms (α‐, β‐, γ‐, and δ‐tocopherol) differing in molecular structure and biological effectiveness. In the seed oil of canola, mainly α‐ and γ‐tocopherol are found with an α/γ‐tocopherol ratio of about 0.5. Three canola populations of doubled haploid lines were grown in three to four field environments to analyze genetic variance and genotype × environment interactions as well as heritability of tocopherols and correlations with other seed components. Significant genotypic differences occur, but large genotype × environment interactions are the major source of variation. Heritability of tocopherol was low in all three populations; the estimates ranged from 0.23 to 0.44 for α‐tocopherol and from 0.33 to 0.50 for γ‐tocopherol. Heritability for tocopherol content is considerably lower than heritability of oil content (0.56–0.90), protein content (0.43–0.76), or glucosinolate content (0.91–0.95). No correlation between α‐ and γ‐tocopherol or between tocopherol and oil, protein, and glucosinolate content was detected. Individual tocopherols can be increased independently of each other and without affecting other major quality traits.

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Genetic variation in N uptake and utilization was investigated in a set of geneticaliy diverse oilseed rape {Brassica napus L.) genotypes, including hybrid, modern, and old cultivars and resynthesized lines. A total of 36 genotypes were grown at seven locations with two levels of N supply: no fertilization and optinnal fertilization (between 160 and 220 kg ha"^ N, depending on regional recomnnendations). The hybrid cultivars had the highest yields and the old land races and resynthesized lines had the lowest yields. This ranking of the various groups was consistent and independent of the N level. Genetic variation exists for both the uptake efficiency and the utilization efficiency. In the presence of low N levels, variation in N use efficiency is mainly due to differences in uptake efficiency whereas differences in utilization efficiency were more important in the presence of high N fertilization.

Resynthesized (Resyn) Brassica napus L. can be used to broaden the genetic diversity and to develop a heterotic genepool for rapeseed hybrid breeding. Domesticated vegetable types are usually employed as B. oleracea parents. We sought to evaluate the potential of wild species as parents for Resyn lines. Fifteen Resyn lines were derived by crossing wild B. oleracea ssp. oleracea and oilseed B. rapa, and 29 Resyn lines were generated from 10 wild Brassica species (B. bourgaei, B. cretica, B. incana, B. insularis, B. hilarionis, B. macrocarpa, B. montana, B. rupestris, B. taurica, B. villosa). Genetic distances were analyzed with AFLP markers for 71 Resyn lines from wild and domesticated B. oleracea, and compared with 55 winter, spring, vegetable, and Asian B. napus genotypes. The genetic distances clearly showed that Resyn lines with wild species provide a genetic diversity absent from the breeding material or Resyn lines from domesticated species. Forty-two Resyn lines were crossed with one or two winter oilseed rape testers, resulting in 64 hybrids that were grown in one year and four locations in Germany and France. The correlation between hybrid yield and genetic distance was slightly negative (r = −0.29). Most of the hybrids with Resyn lines from wild B. oleracea were lower in yield than hybrids with Resyn lines from domesticated B. oleracea. It is promising that Resyn lines descending from unselected wild B. oleracea accessions produced high-yielding hybrids when crossed with adapted genotypes: these Resyn lines would be suited to develop heterotic pools in hybrid breeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-2036-y) contains supplementary material, which is available to authorized users.

Hybrid breeding relies on the combination of parents from two differing heterotic groups. However, the genetic diversity in adapted oilseed rape breeding material is rather limited. Therefore, the use of resynthesized Brassica napus as a distant gene pool was investigated. Hybrids were derived from crosses between 44 resynthesized lines with a diverse genetic background and two male sterile winter oilseed rape tester lines. The hybrids were evaluated together with their parents and check cultivars in 2 years and five locations in Germany. Yield, plant height, seed oil, and protein content were monitored, and genetic distances were estimated with molecular markers (127 polymorphic RFLP fragments). Resynthesized lines varied in yield between 40.9 dt/ha and 21.5 dt/ha, or between 85.1 and 44.6% of check cultivar yields. Relative to check cultivars, hybrids varied from 91.6 to 116.6% in yield and from 94.5 to 103.3% in seed oil content. Mid-parent heterosis varied from −3.5 to 47.2% for yield. The genetic distance of parental lines was not significantly correlated with heterosis or hybrid yield. Although resynthesized lines do not meet the elite rapeseed standards, they are a valuable source for hybrid breeding due to their large distance from present breeding material and their high heterosis when combined with European winter oilseed rape.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-011-1765-7) contains supplementary material, which is available to authorized users.