Envirotyping within a multi-environment trial allowed identifying genetic determinants of winter oilseed rape yield stability.

KEY MESSAGE: A comprehensive environmental characterization allowed identifying stable and interactive QTL for seed yield: QA09 and QC09a were detected across environments; whereas QA07a was specifically detected on the most stressed environments. A main challenge for rapeseed consists in maintaining seed yield while adapting to climate changes and contributing to environmental-friendly cropping systems. Breeding for cultivar adaptation is one of the keys to meet this challenge. Therefore, we propose to identify the genetic determinant of seed yield stability for winter oilseed rape using GWAS coupled with a multi-environmental trial and to interpret them in the light of environmental characteristics. Due to a comprehensive characterization of a multi-environmental trial using 79 indicators, four contrasting envirotypes were defined and used to identify interactive and stable seed yield QTL. A total of four QTLs were detected, among which, QA09 and QC09a, were stable (detected at the multi-environmental trial scale or for different envirotypes and environments); and one, QA07a, was specifically detected into the most stressed envirotype. The analysis of the molecular diversity at QA07a showed a lack of genetic diversity within modern lines compared to older cultivars bred before the selection for low glucosinolate content. The results were discussed in comparison with other studies and methods as well as in the context of breeding programs.

Genomic and phenomic predictions help capture low-effect alleles promoting seed germination in oilseed rape in addition to QTL analyses.

KEY MESSAGE: Phenomic prediction implemented on a large diversity set can efficiently predict seed germination, capture low-effect favorable alleles that are not revealed by GWAS and identify promising genetic resources. Oilseed rape faces many challenges, especially at the beginning of its developmental cycle. Achieving rapid and uniform seed germination could help to ensure a successful establishment and therefore enabling the crop to compete with weeds and tolerate stresses during the earliest developmental stages. The polygenic nature of seed germination was highlighted in several studies, and more knowledge is needed about low- to moderate-effect underlying loci in order to enhance seed germination effectively by improving the genetic background and incorporating favorable alleles. A total of 17 QTL were detected for seed germination-related traits, for which the favorable alleles often corresponded to the most frequent alleles in the panel. Genomic and phenomic predictions methods provided moderate-to-high predictive abilities, demonstrating the ability to capture small additive and non-additive effects for seed germination. This study also showed that phenomic prediction estimated phenotypic values closer to phenotypic values than GEBV. Finally, as the predictive ability of phenomic prediction was less influenced by the genetic structure of the panel, it is worth using this prediction method to characterize genetic resources, particularly with a view to design prebreeding populations.

Identification of transcriptional modules linked to the drought response of Brassica napus during seed development and their mitigation by early biotic stress.

In order to capture the drought impacts on seed quality acquisition in Brassica napus and its potential interaction with early biotic stress, seeds of the 'Express' genotype of oilseed rape were characterized from late embryogenesis to full maturity from plants submitted to reduced watering (WS) with or without pre-occurring inoculation by the telluric pathogen Plasmodiophora brassicae (Pb + WS or Pb, respectively), and compared to control conditions (C). Drought as a single constraint led to significantly lower accumulation of lipids, higher protein content and reduced longevity of the WS-treated seeds. In contrast, when water shortage was preceded by clubroot infection, these phenotypic differences were completely abolished despite the upregulation of the drought sensor RD20. A weighted gene co-expression network of seed development in oilseed rape was generated using 72 transcriptomes from developing seeds from the four treatments and identified 33 modules. Module 29 was highly enriched in heat shock proteins and chaperones that showed a stronger upregulation in Pb + WS compared to the WS condition, pointing to a possible priming effect by the early P. brassicae infection on seed quality acquisition. Module 13 was enriched with genes encoding 12S and 2S seed storage proteins, with the latter being strongly upregulated under WS conditions. Cis-element promotor enrichment identified PEI1/TZF6, FUS3 and bZIP68 as putative regulators significantly upregulated upon WS compared to Pb + WS. Our results provide a temporal co-expression atlas of seed development in oilseed rape and will serve as a resource to characterize the plant response towards combinations of biotic and abiotic stresses.

Genetic control of root morphology in response to nitrogen across rapeseed diversity.

Rapeseed (Brassica napus L.) is an oil-containing crop of great economic value but with considerable nitrogen requirement. Breeding root systems that efficiently absorb nitrogen from the soil could be a driver to ensure genetic gains for more sustainable rapeseed production. The aim of this study is to identify genomic regions that regulate root morphology in response to nitrate availability. The natural variability offered by 300 inbred lines was screened at two experimental locations. Seedlings grew hydroponically with low or elevated nitrate levels. Fifteen traits related to biomass production and root morphology were measured. On average across the panel, a low nitrate level increased the root-to-shoot biomass ratio and the lateral root length. A large phenotypic variation was observed, along with important heritability values and genotypic effects, but low genotype-by-nitrogen interactions. Genome-wide association study and bulk segregant analysis were used to identify loci regulating phenotypic traits. The first approach nominated 319 SNPs that were combined into 80 QTLs. Three QTLs identified on the A07 and C07 chromosomes were stable across nitrate levels and/or experimental locations. The second approach involved genotyping two groups of individuals from an experimental F2 population created by crossing two accessions with contrasting lateral root lengths. These individuals were found in the tails of the phenotypic distribution. Co-localized QTLs found in both mapping approaches covered a chromosomal region on the A06 chromosome. The QTL regions contained some genes putatively involved in root organogenesis and represent selection targets for redesigning the root morphology of rapeseed.

Genetic basis of nitrogen use efficiency and yield stability across environments in winter rapeseed.

BACKGROUND: Nitrogen use efficiency is an important breeding trait that can be modified to improve the sustainability of many crop species used in agriculture. Rapeseed is a major oil crop with low nitrogen use efficiency, making its production highly dependent on nitrogen input. This complex trait is suspected to be sensitive to genotype × environment interactions, especially genotype × nitrogen interactions. Therefore, phenotyping diverse rapeseed populations under a dense network of trials is a powerful approach to study nitrogen use efficiency in this crop. The present study aimed to determine the quantitative trait loci (QTL) associated with yield in winter oilseed rape and to assess the stability of these regions under contrasting nitrogen conditions for the purpose of increasing nitrogen use efficiency. RESULTS: Genome-wide association studies and linkage analyses were performed on two diversity sets and two doubled-haploid populations. These populations were densely genotyped, and yield-related traits were scored in a multi-environment design including seven French locations, six growing seasons (2009 to 2014) and two nitrogen nutrition levels (optimal versus limited). Very few genotype × nitrogen interactions were detected, and a large proportion of the QTL were stable across nitrogen nutrition conditions. In contrast, strong genotype × trial interactions in which most of the QTL were specific to a single trial were found. To obtain further insight into the QTL × environment interactions, genetic analyses of ecovalence were performed to identify the genomic regions contributing to the genotype × nitrogen and genotype × trial interactions. Fifty-one critical genomic regions contributing to the additive genetic control of yield-associated traits were identified, and the structural organization of these regions in the genome was investigated. CONCLUSIONS: Our results demonstrated that the effect of the trial was greater than the effect of nitrogen nutrition levels on seed yield-related traits under our experimental conditions. Nevertheless, critical genomic regions associated with yield that were stable across environments were identified in rapeseed.

Regulation of FATTY ACID ELONGATION1 expression in embryonic and vascular tissues of Brassica napus.

The expression of the FATTY ACID ELONGATION1 genes was characterised to provide insight into the regulation of very long chain fatty acid (VLCFA) biosynthesis in Brassica napus embryos. Each of the two rapeseed homoeologous genes (Bn-FAE1.1 and Bn-FAE1.2) encoding isozymes of 3-keto-acylCoA synthase, a subunit of the cytoplasmic acyl-CoA elongase complex that controls the production of elongated fatty acids, are expressed predominantly in developing seeds. The proximal regions of the Bn-FAE1.1 and Bn-FAE1.2 promoters possess strong sequence identity suggesting that transcriptional control of expression is mediated by this region which contains putative cis-elements characteristic of those found in the promoters of genes expressed in embryo and endosperm. Histochemical staining of rapeseed lines expressing Bn-FAE1.1 promoter:reporter gene fusions revealed a strong expression in the embryo cotyledon and axis throughout the maturation phase. Quantitative analyses revealed the region, -331 to -149, exerts a major control on cotyledon specific expression and the level of expression. A second region, -640 to -475, acts positively to enhance expression levels and extends expression of Bn-FAE1.1 into the axis and hypocotyl but also acts negatively to repress expression in the root meristem. The expression of the Bn-FAE1.1 gene was not restricted to the seed but was also detected in the vascular tissues of germinating seedlings and mature plants in the fascicular cambium tissue present in roots, stem and leaf petiole. We propose that Bn-FAE1.1 expression in vascular tissue may contribute VLCFA for barrier lipid synthesis and reflects the ancestral function of FAE1 encoded 3-keto-acylCoA synthase.

The contrasting N management of two oilseed rape genotypes reveals the mechanisms of proteolysis associated with leaf N remobilization and the respective contributions of leaves and stems to N storage and remobilization during seed filling.

BACKGROUND: Oilseed rape is the third largest oleaginous crop in the world but requires high levels of N fertilizer of which only 50% is recovered in seeds. This weak N use efficiency is associated with a low foliar N remobilization, leading to a significant return of N to the soil and a risk of pollution. Contrary to what is observed during senescence in the vegetative stages, N remobilization from stems and leaves is considered efficient during monocarpic senescence. However, the contribution of stems towards N management and the cellular mechanisms involved in foliar remobilization remain largely unknown. To reach this goal, the N fluxes at the whole plant level from bolting to mature seeds and the processes involved in leaf N remobilization and proteolysis were investigated in two contrasting genotypes (Aviso and Oase) cultivated under ample or restricted nitrate supply. RESULTS: During seed filling in both N conditions, Oase efficiently allocated the N from uptake to seeds while Aviso favoured a better N remobilization from stems and leaves towards seeds. Nitrate restriction decreased seed yield and oil quality for both genotypes but Aviso had the best seed N filling. Under N limitation, Aviso had a better N remobilization from leaves to stems before the onset of seed filling. Afterwards, the higher N remobilization from stems and leaves of Aviso led to a higher final N amount in seeds. This high leaf N remobilization is associated with a better degradation/export of insoluble proteins, oligopeptides, nitrate and/or ammonia. By using an original method based on the determination of Rubisco degradation in the presence of inhibitors of proteases, efficient proteolysis associated with cysteine proteases and proteasome activities was identified as the mechanism of N remobilization. CONCLUSION: The results confirm the importance of foliar N remobilization after bolting to satisfy seed filling and highlight that an efficient proteolysis is mainly associated with (i) cysteine proteases and proteasome activities and (ii) a fine coordination between proteolysis and export mechanisms. In addition, the stem may act as transient storage organs in the case of an asynchronism between leaf N remobilization and N demand for seed filling.

The structural organization of seed oil bodies could explain the contrasted oil extractability observed in two rapeseed genotypes.

MAIN CONCLUSION: The protein, phospholipid and sterol composition of the oil body surface from the seeds of two rapeseed genotypes was compared in order to explain their contrasted oil extractability. In the mature seeds of oleaginous plants, storage lipids accumulate in specialized structures called oil bodies (OBs). These organelles consist of a core of neutral lipids surrounded by a phospholipid monolayer in which structural proteins are embedded. The physical stability of OBs is a consequence of the interactions between proteins and phospholipids. A detailed study of OB characteristics in mature seeds as well as throughout seed development was carried out on two contrasting rapeseed genotypes Amber and Warzanwski. These two accessions were chosen because they differ dramatically in (1) crushing ability, (2) oil extraction yield and, (3) the stability of purified OBs. Warzanwski has higher crushing ability, better oil extraction yield and less stable purified OBs than Amber. OB morphology was investigated in situ using fluorescence microscopy, transmission electron microscopy and pulsed field gradient NMR. During seed development, OB diameter first increased and then decreased 30 days after pollination in both Amber and Warzanwski embryos. In mature seeds, Amber OBs were significantly smaller. The protein, phospholipid and sterol composition of the hemi-membrane was compared between the two accessions. Amber OBs were enriched with H-oleosins and steroleosins, suggesting increased coverage of the OB surface consistent with their higher stability. The nature and composition of phospholipids and sterols in Amber OBs suggest that the hemi-membrane would have a more rigid structure than that of Warzanwski OBs.

Early osmotic adjustment responses in drought-resistant and drought-sensitive oilseed rape.

The impact of osmotic stress on growth, physiology, and metabolism of winter oilseed rape (Brassica napus L.) was investigated by detailed analysis of biomass traits, hormone metabolites and osmolytes in two genetically unrelated drought-tolerant genotypes and two unrelated drought-sensitive genotypes. Seedlings were grown in vitro under controlled conditions and osmotic stress was simulated by applying a gradual treatment with polyethylene glycol (PEG 6000), followed by hypo-osmotic treatment of variants used for metabolite determination. The results provide a basis for the identification of reliable selection criteria for drought resistance in oilseed rape. The in vitro cultivation system established during this study enabled effective discrimination of early osmotic stress responses between drought-resistant and -susceptible oilseed rape genotypes that also show large differences in relative seed yield under drought conditions in the field. Clear physiological and metabolic differences were observed between the drought-resistant and drought-sensitive genotypes, suggesting that osmotic adjustment is a key component of drought response in oilseed rape. Unexpectedly, however, the drought-resistant genotypes did not show typical hormonal adjustment and osmolyte accumulation, suggesting that they possess alternative physiological mechanisms enabling avoidance of stress symptoms.

Crop seed oil bodies: from challenges in protein identification to an emerging picture of the oil body proteome.

Oleaginous seeds store lipids in specialized structures called oil bodies (OBs). These organelles consist of a core of neutral lipids bound by proteins embedded in a phospholipid monolayer. OB proteins are well conserved in plants and have long been grouped into only two categories: structural proteins or enzymes. Recent work, however, which identified other classes of proteins associated with OBs, clearly shows that this classification is obsolete. Proteomics-mediated OB protein identification is facilitated in plants for which the genome is sequenced and annotated. However, it is not clear whether this knowledge can be dependably transposed to less well-characterized plants, including the well-established commercial sources of seed oil as well as the many others being proposed as novel sources for biodiesel, especially in Africa and Asia. Toward an update of the current data available on OB proteins this review discusses (i) the specific difficulties for proteomic studies of organelles; (ii) a 2012 census of the proteins found in seed OBs from various crops; (iii) the oleosin composition of OBs and their role in organelle stability; (iv) PTM of OB proteins as an emerging field of investigation; and finally we describe the emerging model of the OB proteome from oilseed crops.

Genetics and biochemistry of seed flavonoids.

Flavonoids are secondary metabolites that accumulate in most plant seeds and are involved in physiological functions such as dormancy or viability. This review presents a current view of the genetic and biochemical control of flavonoid metabolism during seed development. It focuses mainly on proanthocyanidin accumulation in Arabidopsis, with comparisons to other related metabolic and regulatory pathways. These intricate networks and their fine-tuned regulation, once they are determined, should contribute to a better understanding of seed coat development and the control of PA and flavonol metabolism. In addition, flavonoids provide an interesting model to study various biological processes and metabolic and regulatory networks.

RNA sequencing data for responses to drought stress and/or clubroot infection in developing seeds of Brassica napus.

Oilseed rape (Brassica napus L.) is the third largest oil crop worldwide. Like other crops, oilseed rape faces unfavorable environmental conditions resulting from multiple and combined actions of abiotic and biotic constraints that occur throughout the growing season. In particular drought severely reduces seed yield but also impacts seed quality in oilseed rape. In addition, clubroot disease, caused by the pathogen Plasmodiophora brassicae, limits the yield of the oilseed rape crops grown in infected areas. Clubroot induces swellings or galls on the roots that decrease the flow of water and nutrients within the plant. Furthermore, combinations of different stresses lead to complex plant responses that can not be predicted by the simple addition of individual stress responses. Indeed, an abiotic constraint can either reduce or stimulate the plant response to a pathogen or pest. Transcriptome datasets from different conditions are key resources to improve our knowledge of environmental stress-resistance mechanisms in plant organs. Here, we describe a RNA-seq dataset consisting of 72 samples of immature B. napus seeds from plants grown either under drought, infected with P. brassicae, or a combination of both stresses. A total of 67.6 Gb of transcriptome paired-end reads were filtered, mapped onto the B. napus reference genome Darmor-bzh and used for identification of differentially expressed genes and gene ontology enrichment. The raw reads are available under accession PRJNA738318 at NCBI Sequence Read Archive (SRA) repository. The dataset is a resource for the scientific community exploring seed plasticity.

Dataset for the metabolic and physiological characterization of seeds from oilseed rape (Brassica napus L.) plants grown under single or combined effects of drought and clubroot pathogen Plasmodiophora brassicae.

Faced with the challenges of adapting agriculture to climate change, seed production should have increased resilience to abiotic stress factors and the expected proliferation of pathogens. This concerns both the nutritional quality and seed vigor, two crucial factors in seedling establishment and yield. Both qualities are acquired during seed development, but how environment influences the genetic and physiological determinisms of these qualities remains to be elucidated. With a world production of 71 Mt of seeds per year, oilseed rape (Brassica napus) is the third largest oleaginous crop. But its productivity must cope with several abiotic stresses, among which drought is one of the main constraints in current and future climate scenarios. In addition, clubroot disease, caused by the pathogen Plasmodiophora brassicae, leads to severe yield losses for the Brassica crops worldwide. Clubroot provokes the formation of galls on the infected roots that can restrict the flow of water and nutrients within the plant throughout the growth cycle. In order to get new insights into the impact of single or combined constraints on seed qualities, metabolic profiling assays were run for a collection of 330 seed samples (including developing, mature and imbibed seeds) harvested from plants of two B. napus cultivars ("Express" and "Montego") that were grown under either drought conditions, the presence of P. brassicae, or a combination of both stresses. Metabolites were identified and quantified by UPLC or GC. In addition, monitoring germination traits was conducted for 60 mature seed lots under in vitro conditions using an automated phenotyping platform. The present dataset contains the raw contents for 42 metabolites (nmol.mg-1 of seed dry weight) filtered and analyzed with statistical tests as well as germination speed and percentages. This dataset is available under accession at Data INRAE. These data will contribute to a better understanding of the crosstalk between the plant responses to water deprivation and/or pathogen attack and how it compromises seed quality. A better understanding of the molecular and physiological responses of the seed to (a)biotic stress on a molecular and physiological will be a first step to meet scientific and technological challenges of adapting seeds to their environment.

Identifying and Isolating Meiotic Mutants in a Polyploid Brassica Crop.

This chapter provides a detailed description of TILLING and CRISPR-Cas9 approaches for the purpose of studying genes/factors involved in meiotic recombination in the polyploid species B. napus. The TILLING approach involves the screening and identification of EMS-mutagenized M2 B. napus plants. The strategy for high-throughput plant pooling, the set up for microfluidic PCR and sequencing is provided and the parameters for the analysis of sequence results and the detection of mutants are explained. The CRISPR-Cas system relies on the optimal design of guide RNAs and their efficient expression. The procedure for the generation and detection of knockout mutants is described with the aims to simultaneously target homologous genes.

Corrigendum: FANCM Limits Meiotic Crossovers in Brassica Crops.

[This corrects the article DOI: 10.3389/fpls.2018.00368.].

Protein composition of oil bodies from mature Brassica napus seeds.

Seed oil bodies (OBs) are intracellular particles storing lipids as food or biofuel reserves in oleaginous plants. Since Brassica napus OBs could be easily contaminated with protein bodies and/or myrosin cells, they must be purified step by step using floatation technique in order to remove non-specifically trapped proteins. An exhaustive description of the protein composition of rapeseed OBs from two double-zero varieties was achieved by a combination of proteomic and genomic tools. Genomic analysis led to the identification of sequences coding for major seed oil body proteins, including 19 oleosins, 5 steroleosins and 9 caleosins. Most of these proteins were also identified through proteomic analysis and displayed a high level of sequence conservation with their Arabidopsis thaliana counterparts. Two rapeseed oleosin orthologs appeared acetylated on their N-terminal alanine residue and both caleosins and steroleosins displayed a low level of phosphorylation.

Brassica orthologs from BANYULS belong to a small multigene family, which is involved in procyanidin accumulation in the seed.

As part of a research programme focused on flavonoid biosynthesis in the seed coat of Brassica napus L. (oilseed rape), orthologs of the BANYULS gene that encoded anthocyanidin reductase were cloned in B. napus as well as in the related species Brassica rapa and Brassica oleracea. B. napus genome contained four functional copies of BAN, two originating from each diploid progenitor. Amino acid sequences were highly conserved between the Brassicaceae including B. napus, B. rapa, B. oleracea as well as the model plant Arabidopsis thaliana. Along the 200 bp in 5' of the ATG codon, Bna.BAN promoters (ProBna.BAN) were conserved with AtANR promoter and contained putative cis-acting elements. In addition, transgenic Arabidopsis and oilseed rape plants carrying the first 230 bp of ProBna.BAN fused to the UidA reporter gene were generated. In the two Brassicaceae backgrounds, ProBna.BAN activity was restricted to the seed coat. In B. napus seed, ProBna.BAN was activated in procyanidin-accumulating cells, namely the innermost layer of the inner integument and the micropyle-chalaza area. At the transcriptional level, the four Bna.BAN genes were expressed in the seed. Laser microdissection assays of the seed integuments showed that Bna.BAN expression was restricted to the inner integument, which was consistent with the activation profile of ProBna.BAN. Finally, Bna.BAN genes were mapped onto oilseed rape genetic maps and potential co-localisations with seed colour quantitative trait loci are discussed.

The promoter of the Arabidopsis thaliana BAN gene is active in proanthocyanidin-accumulating cells of the Brassica napus seed coat.

As part of an ongoing research program dedicated to the understanding of proanthocyanidin (PA) accumulation in Brassica napus seed coat, transgenic rapeseed plants carrying a 2.3-kb fragment of the Arabidopsis thaliana BAN promoter (ProAtBAN) fused to the uidA reporter gene (GUS) were generated. Analysis of these plants revealed that ProAtBAN was activated in B. napus seed coat, following a spatio-temporal pattern that was very similar to the PA deposition profile in rapeseed and also to the one previously described in Arabidopsis. ProAtBAN activity occurred as soon as the early stages of embryogenesis and was restricted to the cells where PAs were shown to accumulate. Therefore, the Arabidopsis BAN promoter can be used to trigger gene expression in B. napus seed coat for both genetic engineering and functional validation of candidate genes. In addition, these data strongly suggest that the transcriptional regulatory network of the BAN gene is conserved between Arabidopsis and rapeseed. This is consistent with the fact that similarity searches of the public rapeseed sequence databases allowed recovering the rapeseed homologs for several BAN regulators, namely TT1, TT2, TT8, TT16 and TTG1, which have been previously described in Arabidopsis.

An Integrative Approach to Analyze Seed Germination in Brassica napus.

Seed germination is a complex trait determined by the interaction of hormonal, metabolic, genetic, and environmental components. Variability of this trait in crops has a big impact on seedling establishment and yield in the field. Classical studies of this trait in crops have focused mainly on the analyses of one level of regulation in the cascade of events leading to seed germination. We have carried out an integrative and extensive approach to deepen our understanding of seed germination in Brassica napus by generating transcriptomic, metabolic, and hormonal data at different stages upon seed imbibition. Deep phenotyping of different seed germination-associated traits in six winter-type B. napus accessions has revealed that seed germination kinetics, in particular seed germination speed, are major contributors to the variability of this trait. Metabolic profiling of these accessions has allowed us to describe a common pattern of metabolic change and to identify the levels of malate and aspartate metabolites as putative metabolic markers to estimate germination performance. Additionally, analysis of seed content of different hormones suggests that hormonal balance between ABA, GA, and IAA at crucial time points during this process might underlie seed germination differences in these accessions. In this study, we have also defined the major transcriptome changes accompanying the germination process in B. napus. Furthermore, we have observed that earlier activation of key germination regulatory genes seems to generate the differences in germination speed observed between accessions in B. napus. Finally, we have found that protein-protein interactions between some of these key regulator are conserved in B. napus, suggesting a shared regulatory network with other plant species. Altogether, our results provide a comprehensive and detailed picture of seed germination dynamics in oilseed rape. This new framework will be extremely valuable not only to evaluate germination performance of B. napus accessions but also to identify key targets for crop improvement in this important process.

Genetic and molecular approaches to improve nutritional value of Brassica napus L. seed.

Oilseed rape (Brassica napus L.) is a major oil crop that also supplies proteins for the feed industry. In order to reduce total cost production, the objective is to increase oil yield while reducing crop inputs (especially nitrogen and pesticides). Concomitantly, it is necessary to anticipate specific uses (e.g., fatty acid composition) and to ensure the valorisation of the by-products (rapeseed meal). By the past, improvement of seed quality focused on fatty acid balance and low seed glucosinolate content. Current goals include the breeding of yellow-seeded rapeseed lines with high content of seed oil. The use of molecular tools and the exploitation of Arabidopsis knowledge will be presented and discussed.