An Unexplored Diversity for Adaptation of Germination to High Temperatures in Species.

Elevated temperatures inhibit the germination of a concerning number of crop species. One strategy to mitigate the impact of warming temperatures is to identify and introgress adaptive genes into elite germplasm. Diversity must be sought in wild populations, coupled with an understanding of the complex pattern of adaptation across a broad range of landscapes.

Alternating between even and odd ploidy levels switches on and off the recombination control, even near the centromeres.

Meiotic recombination is a key biological process in plant evolution and breeding, as it generates genetic diversity in each generation through the formation of crossovers (COs). However, due to their importance in genome stability, COs are highly regulated in frequency and distribution. We previously demonstrated that this strict regulation of COs can be modified, both in terms of CO frequency and distribution, in allotriploid Brassica hybrids (2n = 3x = 29; AAC) resulting from a cross between Brassica napus (2n = 4x = 38; AACC) and Brassica rapa (2n = 2x = 20; AA).

A Modified Meiotic Recombination in Largely Improves Its Breeding Efficiency.

Meiotic recombination is the main tool used by breeders to generate biodiversity, allowing genetic reshuffling at each generation. It enables the accumulation of favorable alleles while purging deleterious mutations. However, this mechanism is highly regulated with the formation of one to rarely more than three crossovers, which are not randomly distributed.

Sequencing and Chromosome-Scale Assembly of Plant Genomes, as a Use Case.

With the rise of long-read sequencers and long-range technologies, delivering high-quality plant genome assemblies is no longer reserved to large consortia. Not only sequencing techniques, but also computer algorithms have reached a point where the reconstruction of assemblies at the chromosome scale is now feasible at the laboratory scale. Current technologies, in particular long-range technologies, are numerous, and selecting the most promising one for the genome of interest is crucial to obtain optimal results.

Long-read assembly of the Brassica napus reference genome Darmor-bzh.

Background: The combination of long reads and long-range information to produce genome assemblies is now accepted as a common standard. This strategy not only allows access to the gene catalogue of a given species but also reveals the architecture and organization of chromosomes, including complex regions such as telomeres and centromeres. The Brassica genus is not exempt, and many assemblies based on long reads are now available.

Cytonuclear interactions remain stable during allopolyploid evolution despite repeated whole-genome duplications in Brassica.

Several plastid macromolecular protein complexes are encoded by both nuclear and plastid genes. Therefore, cytonuclear interactions are held in place to prevent genomic conflicts that may lead to incompatibilities. Allopolyploidy resulting from hybridization and genome doubling of two divergent species can disrupt these fine-tuned interactions, as newly formed allopolyploid species confront biparental nuclear chromosomes with a uniparentally inherited plastid genome.

Chromosome-scale assemblies of plant genomes using nanopore long reads and optical maps.

Plant genomes are often characterized by a high level of repetitiveness and polyploid nature. Consequently, creating genome assemblies for plant genomes is challenging. The introduction of short-read technologies 10 years ago substantially increased the number of available plant genomes.

Multi-year linkage and association mapping confirm the high number of genomic regions involved in oilseed rape quantitative resistance to blackleg.

A repertoire of the genomic regions involved in quantitative resistance to Leptosphaeria maculans in winter oilseed rape was established from combined linkage-based QTL and genome-wide association (GWA) mapping. Linkage-based mapping of quantitative trait loci (QTL) and genome-wide association studies are complementary approaches for deciphering the genomic architecture of complex agronomical traits. In oilseed rape, quantitative resistance to blackleg disease, caused by L.

The Impact of Open Pollination on the Structural Evolutionary Dynamics, Meiotic Behavior, and Fertility of Resynthesized Allotetraploid L.

Allopolyploidy, which results from the merger and duplication of two divergent genomes, has played a major role in the evolution and diversification of flowering plants. The genomic changes that occur in resynthesized or natural neopolyploids have been extensively studied, but little is known about the effects of the reproductive mode in the initial generations that may precede its successful establishment. To truly reflect the early generations of a nascent polyploid, two resynthesized allotetraploid populations were obtained for the first time by open pollination.

Comparative genomic analysis of duplicated homoeologous regions involved in the resistance of Brassica napus to stem canker.

All crop species are current or ancient polyploids. Following whole genome duplication, structural and functional modifications result in differential gene content or regulation in the duplicated regions, which can play a fundamental role in the diversification of genes underlying complex traits. We have investigated this issue in Brassica napus, a species with a highly duplicated genome, with the aim of studying the structural and functional organization of duplicated regions involved in quantitative resistance to stem canker, a disease caused by the fungal pathogen Leptosphaeria maculans.

Homoeologous duplicated regions are involved in quantitative resistance of Brassica napus to stem canker.

Background: Several major crop species are current or ancient polyploids. To better describe the genetic factors controlling traits of agronomic interest (QTL), it is necessary to understand the structural and functional organisation of these QTL regions in relation to genome duplication. We investigated quantitative resistance to the fungal disease stem canker in Brassica napus, a highly duplicated amphidiploid species, to assess the proportion of resistance QTL located at duplicated positions.

High-density SNP-based genetic map development and linkage disequilibrium assessment in Brassica napus L.

Background: High density genetic maps built with SNP markers that are polymorphic in various genetic backgrounds are very useful for studying the genetics of agronomical traits as well as genome organization and evolution. Simultaneous dense SNP genotyping of segregating populations and variety collections was applied to oilseed rape (Brassica napus L.) to obtain a high density genetic map for this species and to study the linkage disequilibrium pattern.

A dominant point mutation in a RINGv E3 ubiquitin ligase homoeologous gene leads to cleistogamy in Brassica napus.

In the allopolyploid Brassica napus, we obtained a petal-closed flower mutation by ethyl methanesulfonate mutagenesis. Here, we report cloning and characterization of the Bn-CLG1A (CLG for cleistogamy) gene and the Bn-clg1A-1D mutant allele responsible for the cleistogamy phenotype. Bn-CLG1A encodes a RINGv E3 ubiquitin ligase that is highly conserved across eukaryotes.

Integration of linkage maps for the Amphidiploid Brassica napus and comparative mapping with Arabidopsis and Brassica rapa.

Background: The large number of genetic linkage maps representing Brassica chromosomes constitute a potential platform for studying crop traits and genome evolution within Brassicaceae. However, the alignment of existing maps remains a major challenge. The integration of these genetic maps will enhance genetic resolution, and provide a means to navigate between sequence-tagged loci, and with contiguous genome sequences as these become available.

A sequence-tagged genetic map for the brown alga Ectocarpus siliculosus provides large-scale assembly of the genome sequence.

• Ectocarpus siliculosus has been proposed as a genetic and genomic model for the brown algae and the 214  Mbp genome of this organism has been sequenced. The aim of this project was to obtain a chromosome-scale view of the genome by constructing a genetic map using microsatellite markers that were designed based on the sequence supercontigs. • To map genetic markers, a segregating F(2) population was generated from a cross between the sequenced strain (Ec 32) and a compatible strain from northern Chile.

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).

Molecular and phenotypic characterization of near isogenic lines at QTL for quantitative resistance to Leptosphaeria maculans in oilseed rape (Brassica napus L.).

The most common and effective way to control phoma stem canker (blackleg) caused by Leptosphaeria maculans in oilseed rape (Brassica napus) is by breeding resistant cultivars. Specific resistance genes have been identified in B. napus and related species but in some B.

A concise synthesis of 5-amino-5-deoxyaldonic acids as monomers for the preparation of nylon 5.

Saponification of 5-azido-5-deoxy-D-pentonolactones (ribo-, arabino-, xylo-) with NaOH gave the corresponding 5-azido-5-deoxyaldonic acids sodium salts which, after regeneration of the acid form followed by catalytic reduction, led to the target compounds in 98% overall yields.

Genetic control of oil content in oilseed rape (Brassica napus L.).

In oilseed rape (Brassica napus L.) like in most oleaginous crops, seed oil content is the main qualitative determinant that confers its economic value to the harvest. Increasing seed oil content is then still an important objective in oilseed rape breeding.