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Germination, the process whereby a dry, quiescent seed springs to life, has been a focus of plant biologist for many years, yet the early events following water uptake, during which metabolism of the embryo is restarted, remain enigmatic. Here, the nature of the cues required for this restarting in oilseed rape (Brassica napus) seed has been investigated. A holistic in vivo approach was designed to display the link between the entry and allocation of water, metabolic events and structural changes occurring during germination. For this, we combined functional magnetic resonance imaging with Fourier transform infrared microscopy, fluorescence-based respiration mapping, computer-aided seed modeling and biochemical tools. We uncovered an endospermal lipid gap, which channels water to the radicle tip, from whence it is distributed via embryonic vasculature toward cotyledon tissues. The resumption of respiration is initiated first in the endosperm, only later spreading to the embryo. Sugar metabolism and lipid utilization are linked to the spatiotemporal sequence of tissue rehydration. Together, this imaging study provides insights into the spatial aspects of key events in oilseed rape seeds leading to germination. It demonstrates how seed architecture predetermines the pattern of water intake, which sets the stage for the orchestrated restart of life.

This chapter contains sections titled: Introduction Pathways of Gene Flow in Oilseed Rape Managing Gene Flow in Oilseed Rape Combining Biological Measures Package for Gene Containment Conclusion Acknowledgments References

The effects of intense heat during the reproductive phase of two Brassica species-B. napus and C. sativa-could be alleviated by a prior gradual increase exposure and/or PGPR inoculation. Abct. Among extreme weather events caused by climate change, heat waves are one of the most threatening issues for food security. Heat stress is known to be particularly penalizing at the reproductive stage for oleaginous crops, such as oilseed rape and camelina, and is responsible for crop failures as a consequence of yield losses and lower quality of harvest plants parts. In this context, our study aims to analyze two acclimation strategies that rely on the induction of signals prior to an intense heat stress event, i.e., thermopriming (herein, a gradual increase in temperature) and bacteria inoculations (herein, two Plant Growth-Promoting Rhizobacteria (PGPR) were tested). In the two experiments, we assessed the expected beneficial effects of these two acclimation strategies on yield components, seed quality criteria (nutritional and related to dormancy). While thermopriming improved heat stress tolerance in B. napus cv Aviso by maintaining yield, seed nutritional quality and seed dormancy, the effects of the gradual increase prior to the heat stress were even more negative than the later intense heat stress event in C. sativa cv Calena which resulted in cumulated negative effects. The experimentation based on PGPR inoculation highlighted similar trends to thermopriming in B. napus cv Aviso but to a lesser extent. However, in C. sativa cv Calena, very weak effects of PGPR inoculation upon heat stress were observed. Finally, these two acclimation strategies were shown to help alleviate the impacts of intense heat stress but in a species-dependent manner. This study should be deepened by exploring the behaviors of more cultivars of oilseed rape and camelina in the perspective to generalize these results at the species scale.

The seed germination and seedling growth of rapeseed are crucial stages in plant life, especially when facing abiotic stresses. In the present work, the effects of water and temperature on seed germination and seedling growth were investigated in a rapeseed crop (Brassica napus L.). The plants were examined under different temperature levels (5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C) and water levels (twenty-nine levels based on either one-milliliter intervals or as a percentage of the thousand-kernel weight (TKW)). Moreover, planting densities and antifungal application techniques were investigated in the study. The findings demonstrated substantial variations between all the growth parameters investigated at all the tested temperatures, and 20 °C was considered the optimum within a broad range of 15–25 °C. Water availability plays a significant role in germination, which can be initiated at 0.65 mL, corresponding to 500% of the TKW. The method of TKW is a more accurate aspect of water application because of the consideration of the seed weight and size. The optimal water range for the accumulation of dry weight, 3.85–5.9 mL (2900–4400% of TKW), was greater than that required for seedling growth, 1.45–3.05 mL (1100–2300% of TKW). Twenty to twenty-five seeds per 9 cm Petri dish exhibited the most outstanding values compared to the others, which provides an advantage in breeding programs, especially when there are seed limitations. Seed priming is a more effective antifungal application strategy. These data can be incorporated into future rapeseed germination in vitro studies, breeding programs, and sowing date predictions.

Yellow seed is a desirable trait with great potential for improving seed quality in Brassica crops. Unfortunately, no natural or induced yellow seed germplasms have been found in Brassica napus, an important oil crop, which likely reflects its genome complexity and the difficulty of the simultaneous random mutagenesis of multiple gene copies with functional redundancy. Here, we demonstrate the first application of CRISPR/Cas9 for creating yellow‐seeded mutants in rapeseed. The targeted mutations of the BnTT8 gene were stably transmitted to successive generations, and a range of homozygous mutants with loss‐of‐function alleles of the target genes were obtained for phenotyping. The yellow‐seeded phenotype could be recovered only in targeted mutants of both BnTT8 functional copies, indicating that the redundant roles of BnA09.TT8 and BnC09.TT8b are vital for seed colour. The BnTT8 double mutants produced seeds with elevated seed oil and protein content and altered fatty acid (FA) composition without any serious defects in the yield‐related traits, making it a valuable resource for rapeseed breeding programmes. Chemical staining and histological analysis showed that the targeted mutations of BnTT8 completely blocked the proanthocyanidin (PA)‐specific deposition in the seed coat. Further, transcriptomic profiling revealed that the targeted mutations of BnTT8 resulted in the broad suppression of phenylpropanoid/flavonoid biosynthesis genes, which indicated a much more complex molecular mechanism underlying seed colour formation in rapeseed than in Arabidopsis and other Brassica species. In addition, gene expression analysis revealed the possible mechanism through which BnTT8 altered the oil content and fatty acid composition in seeds.

Oilseed rape (Brassica napus L.) was formed ~7500 years ago by hybridization between B. rapa and B. oleracea, followed by chromosome doubling, a process known as allopolyploidy. Together with more ancient polyploidizations, this conferred an aggregate 72× genome multiplication since the origin of angiosperms and high gene content. We examined the B. napus genome and the consequences of its recent duplication. The constituent An and Cn subgenomes are engaged in subtle structural, functional, and epigenetic cross-talk, with abundant homeologous exchanges. Incipient gene loss and expression divergence have begun. Selection in B. napus oilseed types has accelerated the loss of glucosinolate genes, while preserving expansion of oil biosynthesis genes. These processes provide insights into allopolyploid evolution and its relationship with crop domestication and improvement.

Key message A set of additive loci for seed oil content were identified using association mapping and one of the novel loci on the chromosome A5 was validated by linkage mapping. Increasing seed oil content is one of the most important goals in the breeding of oilseed crops including Brassica napus , yet the genetic basis for variations in this important trait remains unclear. By genome-wide association study of seed oil content using 521 B. napus accessions genotyped with the Brassica 60K SNP array, we identified 50 loci significantly associated with seed oil content using three statistical models, the general linear model, the mixed linear model and the Anderson–Darling test. Together, the identified loci could explain approximately 80 % of the total phenotypic variance, and 29 of these loci have not been reported previously. Furthermore, a novel locus on the chromosome A5 that could increase 1.5–1.7 % of seed oil content was validated in an independent bi-parental linkage population. Haplotype analysis showed that the favorable alleles for seed oil content exhibit cumulative effects. Our results thus provide valuable information for understanding the genetic control of seed oil content in B. napus and may facilitate marker-based breeding for a higher seed oil content in this important oil crop.

Drought poses serious threats to global crop production and its intensity is continuously soaring due to global warming. Brassica napus L. is an essential oilseed crop with an important place in global edible oil production. Drought-induced yield reduction is a big problem that needs to be addressed by knowing the targeted pathways and processes. Drought stress adversely affects germination, seedling establishment, photosynthetic efficiency, mineral uptake, shoot elongation, seed development, yield and quality in rapeseed. Plants attain various physiological and molecular protective approaches for tolerance under drought stress. The currently existing agronomic, breeding and biotechnological approaches can increase the adaptability provision of a conducive environment to Brassica plants facing drought stress. In the present review, we addressed the possible cross-talk among various responses of rapeseed under drought stress and discussed the potential management strategies for regulating the drought tolerance-related mechanisms. To date, various novel approaches have been tested to minimize the adverse effects of environmental stresses in B. napus . Despite the main improvements, there is still a big room for improvement in the drought tolerance of rapeseed cultivars. Thus, future research mainly using biotechnological and molecular approaches should be carried out to develop genetically engineered rapeseed plants with enhanced drought tolerance.

Seed yield is a complex trait for many crop species including oilseed rape (OSR) ( Brassica napus ), the second most important oilseed crop worldwide. Studies have focused on the contribution of distinct factors in seed yield such as environmental cues, agronomical practices, growth conditions, or specific phenotypic traits at the whole plant level, such as number of pods in a plant. However, how female reproductive traits contribute to whole plant level traits, and hence to seed yield, has been largely ignored. Here, we describe the combined contribution of 33 phenotypic traits within a B. napus diversity set population and their trade-offs at the whole plant and organ level, along with their interaction with plant level traits. Our results revealed that both Winter OSR (WOSR) and Spring OSR (SOSR); the two more economically important OSR groups in terms of oil production; share a common dominant reproductive strategy for seed yield. In this strategy, the main inflorescence is the principal source of seed yield, producing a good number of ovules, a large number of long pods with a concomitantly high number of seeds per pod. Moreover, we observed that WOSR opted for additional reproductive strategies than SOSR, presenting more plasticity to maximise seed yield. Overall, we conclude that OSR adopts a key strategy to ensure maximal seed yield and propose an ideal ideotype highlighting crucial phenotypic traits that could be potential targets for breeding.

The introduction of high-yielding and hybrid cultivars and the opening of new markets in the food and feed sector have steadily increased rapeseed production since the 1980s in the main production regions, Canada, Europe, China, India, and Australia. Since the 1990s, however, the average growth rate of yields has declined in Europe and Australia, which has been associated with a less effective control of biotic stresses. A global survey including the knowledge of 22 experts from 10 countries revealed a total of 16 diseases, 37 insect pests, several species of nematodes, and slugs currently affecting rapeseed production globally. A ranking of the top 10 most important biotic stresses in the four global regions where Brassica napus is grown (Canada, China, Europe, Australia) indicated an increase in several important stresses and distinct regional differences in the priority of prevailing diseases and pests. A stronger overlap exists among diseases, with Sclerotinia stem rot, Phoma stem canker, and clubroot occurring in all the four global regions on the top 10 list, while the range of prevailing insect pests was more diverse among the regions, with no top 10 insect playing an equally important role worldwide. Management options are substantially broader in disease than in pest control, making the latter the larger challenge. Since common integrated pest management (IPM) tools such as crop rotation, soil management, resistant cultivars or biocontrol are ineffective or not available, insect control largely relies on insecticides. Increasing restrictions on insecticide use, particularly in Europe, and losses in insecticide efficacy threaten the profitability of oilseed rape production and its role as an important break crop in cereal dominated cropping systems. Since the survival time of insects in the absence of their main host is relatively short (<1 year), a regional synchronization of cropping schemes resulting in one or more years without the crop could lead to a substantial disruption of regional insect populations. If rotation schemes were implemented on the landscape instead the farm level, by coordination among growers in zones covering the range distances of insect pests, an efficient and chemical low management strategy could be established and enable a more sustainable rapeseed production in the future.