Association mapping can quickly and efficiently dissect complex agronomic traits. Rapeseed is one of the most economically important polyploid oil crops, although its genome sequence is not yet published. In this study, a recently developed 60K Brassica Infinium® SNP array was used to analyse an association panel with 472 accessions. The single-nucleotide polymorphisms (SNPs) of the array were in silico mapped using ‘pseudomolecules’ representative of the genome of rapeseed to establish their hypothetical order and to perform association mapping of seed weight and seed quality. As a result, two significant associations on A8 and C3 of Brassica napus were detected for erucic acid content, and the peak SNPs were found to be only 233 and 128 kb away from the key genes BnaA.FAE1 and BnaC.FAE1. BnaA.FAE1 was also identified to be significantly associated with the oil content. Orthologues of Arabidopsis thaliana HAG1 were identified close to four clusters of SNPs associated with glucosinolate content on A9, C2, C7 and C9. For seed weight, we detected two association signals on A7 and A9, which were consistent with previous studies of quantitative trait loci mapping. The results indicate that our association mapping approach is suitable for fine mapping of the complex traits in rapeseed.

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Preterm neonates are exposed to extrauterine environmental Ags during the time period that corresponds to the last trimester of normal intrauterine development. To study whether this precocious exposure to Ags accelerates the Ig repertoire diversification, we compared IgH chain genes of preterm neonates (gestational age, 25–29 wk) during their first postnatal months with those of term neonates. Preterm infants approaching their expected date of delivery after 8–13 wk of extrauterine life used a similar VH, DH, and JH gene segment repertoire as term neonates born after intrauterine development. Furthermore, the length increase of the NDN region between VH and JH by 0.25 nt per gestational week (r = 0.556, p < 0.0001) was not accelerated. Thus, the generation of the VH region gene repertoire is developmentally controlled and independent of environmental influences. However, exposure to extrauterine Ags induced class switch and somatic mutations in IgH chain genes within 2 wk after premature birth and IgG transcript diversity and mutational frequency increased with the duration of extrauterine life. Three-month-old preterm infants expressed a heterogeneous IgG repertoire at their expected date of delivery with VH region genes carrying significant numbers of somatic mutations with evidence for Ag selection. Term neonates, however, had no such IgG repertoire. We conclude that restrictions in the neonatal Ig VH region gene repertoire persist until term despite exposure to environmental Ags. Yet, many weeks before term the immune system of the preterm neonate can already support germinal center reactions in response to environmental Ags.