Rapeseed Germplasm Research Articles

Genome assembly and genomic architecture of a prominent cold‐resistant rapeseed germplasm

Genome assembly and genomic architecture of a prominent cold‐resistant rapeseed germplasm

Root system architecture change in response to waterlogging stress in a 448 global collection of rapeseeds (Brassica napus L.).

A novel image-based screening method for precisely identifying genotypic variations in rapeseed RSA under waterlogging stress was developed. Five key root traits were confirmed as good indicators of waterlogging and might be employed in breeding, particularly when using the MFVW approach. Waterlogging is a vital environmental factor that has detrimental effects on the growth and development of rapeseed (Brassica napus L.). Plant roots suffer from hypoxia under waterlogging, which ultimately confers yield penalty. Therefore, it is crucially important to understand the genetic variation of root system architecture (RSA) in response to waterlogging stress to guide the selection of new tolerant cultivars with favorable roots. This research was conducted to investigate RSA traits using image-based screening techniques to better understand how RSA changes over time during waterlogging at the seedling stage. First, we performed a t-test by comparing the relative root trait value between four tolerant and four sensitive accessions. The most important root characteristics associated with waterlogging tolerance at 12 h are total root length (TRL), total root surface area (TRSA), total root volume (TRV), total number of tips (TNT), and total number of forks (TNF). The root structures of 448 rapeseed accessions with or without waterlogging showed notable genetic diversity, and all traits were generally restrained under waterlogging conditions, except for the total root average diameter. Additionally, according to the evaluation and integration analysis of 448 accessions, we identified that five traits, TRL, TRSA, TRV, TNT, and TNF, were the most reliable traits for screening waterlogging-tolerant accessions. Using analysis of the membership function value (MFVW) and D-value of the five selected traits, 25 extremely waterlogging-tolerant materials were screened out. Waterlogging significantly reduced RSA, inhibiting root growth compared to the control. Additionally, waterlogging increased lipid peroxidation, accompanied by a decrease in the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). This study effectively improves our understanding of the response of RSA to waterlogging. The image-based screening method developed in this study provides a new scientific guidance for quickly examining the basic RSA changes and precisely predicting waterlogging-tolerant rapeseed germplasms, thus expanding the genetic diversity of waterlogging-tolerant rapeseed germplasm available for breeding.

Identification of a major QTL and candidate genes analysis for branch angle in rapeseed (Brassica napus L.) using QTL-seq and RNA-seq.

Branching angle is an essential trait in determining the planting density of rapeseed (Brassica napus L.) and hence the yield per unit area. However, the mechanism of branching angle formation in rapeseed is not well understood. In this study, two rapeseed germplasm with extreme branching angles were used to construct an F2 segregating population; then bulked segregant analysis sequencing (BSA-seq) and quantitative trait loci (QTL) mapping were utilized to localize branching anglerelated loci and combined with transcriptome sequencing (RNA-seq) and quantitative real-time PCR (qPCR) for candidate gene mining. A branching angle-associated quantitative trait loci (QTL) was mapped on chromosome C3 (C3: 1.54-2.65 Mb) by combining BSA-seq as well as traditional QTL mapping. A total of 54 genes had SNP/Indel variants within the QTL interval were identified. Further, RNA-seq of the two parents revealed that 12 of the 54 genes were differentially expressed between the two parents. Finally, we further validated the differentially expressed genes using qPCR and found that six of them presented consistent differential expression in all small branching angle samples and large branching angles, and thus were considered as candidate genes related to branching angles in rapeseed. Our results introduce new candidate genes for the regulation of branching angle formation in rapeseed, and provide an important reference for the subsequent exploration of its formation mechanism.

Low CO2 concentration, a key environmental factor for developing plateau adapted rapeseed

BackgroundPhotosynthesis is a fundamental process that underlies the formation of crop yield, wherein light serves as the driving force and carbon dioxide (CO2) as the raw material. These two factors have a direct influence on the progress and efficiency of photosynthesis in crops. Rapeseed is one of the four major oilseed crops worldwide. Plateau rapeseed has now become a research hotspot. However, the lack of high-yielding rapeseed germplasm resources on the plateau and the highly efficient strategy for screening them severely affect the development of rapeseed industry in plateau.ResultsIn the rapeseed experimental fields located on the plateau (Lhasa, Tibet), we measured abundant sunlight, characterized by an average daily photosynthetically active radiation (PAR) of 1413 μmol m−2 s−1. In addition, the atmospheric CO2 concentrations range from 300 to 400 ppm, which is only two-thirds of that in the plain (Chengdu, Sichuan). We found that under different measurement conditions of light intensity and CO2 concentration, different rapeseed genotypes showed significant differences in leaf photosynthetic efficiency during the seedling stage. Moreover, the rapeseed materials with high photosynthetic efficiency under low CO2 concentrations rather than high light intensity, exhibited significant advantages in biomass, yield, and oil content when cultivated on the plateau, indicating that the CO2 is the key environmental factor which limited rapeseed production in plateau. Based on photosynthetic efficiency screening under low CO2 concentrations, six rapeseed varieties SC3, SC10, SC25, SC27, SC29 and SC37, shown significantly higher yields in plateau environment compared to local control variety were obtained. In addition, the adaptability of rapeseed to plateau was found to be related to the activities of key Calvin cycle enzymes and the accumulation of photosynthetic products.ConclusionsThis study established a screening strategy for plateau high-yielding rapeseed materials, obtained six varieties which were suitable for plateau cultivation, explored the mechanism of rapeseed response to the plateau environment, and thus provides a feasible strategy for plateau-adapted rapeseed breeding.

Segmentation and Phenotype Calculation of Rapeseed Pods Based on YOLO v8 and Mask R-Convolution Neural Networks.

Rapeseed is a significant oil crop, and the size and length of its pods affect its productivity. However, manually counting the number of rapeseed pods and measuring the length, width, and area of the pod takes time and effort, especially when there are hundreds of rapeseed resources to be assessed. This work created two state-of-the-art deep learning-based methods to identify rapeseed pods and related pod attributes, which are then implemented in rapeseed pots to improve the accuracy of the rapeseed yield estimate. One of these methods is YOLO v8, and the other is the two-stage model Mask R-CNN based on the framework Detectron2. The YOLO v8n model and the Mask R-CNN model with a Resnet101 backbone in Detectron2 both achieve precision rates exceeding 90%. The recognition results demonstrated that both models perform well when graphic images of rapeseed pods are segmented. In light of this, we developed a coin-based approach for estimating the size of rapeseed pods and tested it on a test dataset made up of nine different species of Brassica napus and one of Brassica campestris L. The correlation coefficients between manual measurement and machine vision measurement of length and width were calculated using statistical methods. The length regression coefficient of both methods was 0.991, and the width regression coefficient was 0.989. In conclusion, for the first time, we utilized deep learning techniques to identify the characteristics of rapeseed pods while concurrently establishing a dataset for rapeseed pods. Our suggested approaches were successful in segmenting and counting rapeseed pods precisely. Our approach offers breeders an effective strategy for digitally analyzing phenotypes and automating the identification and screening process, not only in rapeseed germplasm resources but also in leguminous plants, like soybeans that possess pods.

A novel type of Brassica napus with higher stearic acid in seeds developed through genome editing of BnaSAD2 family.

Modifications of multiple copies of the BnaSAD2 gene family with genomic editing technology result in higher stearic acid content in the seed of polyploidy rapeseed. Solid fats from vegetable oils are widely used in food processing industry. Accumulating data showed that stearic acid is more favorite as the major composite among the saturate fatty acids in solid fats in considerations of its effects on human health. Rapeseed is the third largest oil crop worldwide, and has potential to be manipulated to produce higher saturated fatty acids as raw materials of solid fats. Toward that end, we identified four SAD2 gene family members in B. napus genome and established spatiotemporal expression pattern of the BnaSAD2 members. Genomic editing technology was applied to mutate all the copies of BnaSAD2 in this allopolyploid species and mutants at multiple alleles were generated and characterized to understand the effect of each BnaSAD2 member on blocking desaturation of stearic acid. Mutations occurred at BnaSAD2.A3 resulted in more dramatic changes of fatty acid profile than ones on BnaSAD2.C3, BnaSAD2.A5 and BnaSAD2.C4. The content of stearic acid in mutant seeds with single locus increased dramatically with a range of 3.1-8.2%. Furthermore, combination of different mutated alleles of BnaSAD2 resulted in more dramatic changes in fatty acid profiles and the double mutant at BnaSAD2.A3 and BnaSAD2.C3 showed the most dramatic phenotypic changes compared with its single mutants and other double mutants, leading to 11.1% of stearic acid in the seeds. Our results demonstrated that the members of BnaSAD2 have differentiated in their efficacy as a Δ9-Stearoyl-ACP-Desaturase and provided valuable rapeseed germplasm for breeding high stearic rapeseed oil.

Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise, the threat of heat stress to rapeseed production is becoming more obvious. Exploring the response characteristics of two important biological pathways, oil accumulation and photosynthesis, to heat stress during B. napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed. The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B. napus germplasms with different oil content and environmental sensitivity, including 6 rapeseed varieties which exhibited environment-sensitive/insensitive and with high, medium or low oil content, were tested by whole plant heat stress or the in vitro silique culture system. Both assay exhibited similar trend on oil content of the rapeseed germplasms. The heat effect on the chlorophyll fluorescence kinetic parameters Fv/Fm, ETR and Y(II) were also consistent. Heat stress significantly decreased oil content, although there was abundant genetic variation on heat tolerance among the genotypes. Correlation analysis showed that the decrease rate of Fv/Fm of silique heat-stressed B. napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed (R = 0.9214, P-value < 0.01). Overall, the results indicated that heat stress inhibited oil accumulation and photosynthesis in B. napus developing seed. The decrease rate of chlorophyll fluorescence parameter Fv/Fm of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification. Further, two heat insensitive rapeseed varieties with high oil content were identified.

Comprehensive evaluation of high-oleic rapeseed (Brassica napus) based on quality, resistance, and yield traits: A new method for rapid identification of high-oleic acid rapeseed germplasm.

To scientifically evaluate and utilize high-oleic acid rape germplasm resources and cultivate new varieties suitable for planting in the Hunan Province, 30 local high-oleic acid rape germplasms from Hunan were used as materials. The 12 personality indices of quality, yield, and resistance were comprehensively evaluated by variability, correlation, principal component, and cluster analyses. The results of variability showed that except for oleic acid, the lowest coefficient of variation was oil content, which was 0.06. Correlation analysis showed that oil content was positively correlated with main traits such as yield per plant and oleic acid, which could be used in the early screening of high-oleic rape germplasm. The results of principal component analysis showed that the 12 personality indicators were integrated into four principal components, and the cumulative contribution rate was 62.487%. The value of comprehensive coefficient 'F' was positively correlated with the first, second, and fourth principal components and negatively correlated with the third principal component. Cluster analysis showed that 30 high-oleic rape germplasms could be divided into four categories consisting of 9 (30%), 6 (20%), 7 (23%), and 8 (27%) high-oleic rape germplasms, each with the characteristics of "high disease resistance", "high yield", "high protein", and "more stability". This study not only provides a reference basis for high-oleic rape breeding but also provides a theoretical basis for their early screening.

Screening of salt tolerance traits and the salt tolerance evaluation method in &lt;em&gt;Brassica napus&lt;/em&gt; at the seed germination stage

Soil salinity is one of the major abiotic stresses that negatively affect plant growth and agricultural productivity. For many crop species, the germination stage is one of the most sensitive stages to salinity stress. This study evaluated salt tolerance in 200 Brassica napus L. germplasms using hierarchical cluster analysis based on multiple morphological parameters, including germination rate, root length, fresh weight of root, shoot length, fresh weight of shoot, and total fresh weight. Membership function was used as a comprehensive index to select and evaluate salt tolerance of these germplasms, identifying 8 highly salt-tolerant germplasms, 40 salt-tolerant germplasms, 65 moderate salt-tolerant germplasms, 52 salt-sensitive germplasms, and 35 highly saltsensitive germplasms lines. The responses of rapeseed germplasm to salt stress indicate differences in morphological parameters. Furthermore, NaCl showed a positive effect on total fresh weight and biomass production of some germplasms at a concentration of 100 mmol L–1. Since the correlation value of salt tolerance with total fresh weight was highest under 200 mmol L–1 NaCl, it can be considered the most reliable parameter to evaluate salt tolerance. Therefore, the findings of this study can be applied as an effective and reliable method for mass screening and evaluation of Brassica napus germplasm at the germination stage for breeding salt-tolerant rapeseed genotypes. Highlights - The salinity tolerance of 200 varieties of B. napus germplasms was investigated. - B. napus is more vulnerable to saline conditions during the germination and early reproductive stages than the vegetative and flowering periods. - Based on hierarchical cluster analysis, there was a wide variability of salinity tolerance among rapeseed germplasm. - Low concentration of sodium chloride had a positive effect on shoot and root growth, germination and total weight in some B. napus seedlings. - Total fresh weight can be utilized as the most efficient index for mass screening of salt tolerance in B. napus germplasms at the germination stage.

Screening of rapeseed germplasms with low nitrogen tolerance and the evaluation of its potential application as green manure

<p id="C3">Rapeseed (<italic>Brassica napus</italic> L.) is the major edible oil crop in China, and it is also a kind of crop for land use and maintenance, crop rotation, and fallow. With the promotion of green development in agriculture, rapeseed is highlighted with its high quality as green manure due to the characteristics of great biomass and adaptability. For the different industrial objectives of rapeseed cultivation, the nutrient demand characteristics of the existing rapeseed varieties determine the high recommended fertilization levels, whereas it cannot meet the needs of green manure with low fertilizer input. Therefore, the evaluation and screening of rapeseed germplasms with low nitrogen (N) tolerance can provide material support for breeding rapeseed cultivars as green manure. In this study, 73 rapeseed germplasms were planted at two N levels (low N and normal N) in the field experiment, the potential application as green manure of different rapeseed germplasms were evaluated by fresh weight, nutrient accumulation, and tolerance index at full flowering stage. Results showed that the change of fresh weight per plant for 73 rapeseed germplasms under low N conditions ranged from 29.33 g to 199.33 g, and the variation coefficient was 30.0%. Meanwhile, under low N stress, the change of N accumulation in shoot and root of 73 rapeseed germplasms were ranged from 48.67-360.43 mg and 4.21-67.46 mg per plant, and the variation coefficient were 31.0% and 53.0%, respectively. This mean that there were certain genetic variations biomass and nutrient absorption and accumulation ability among different rapeseed germplasms. Therefore, it was feasible to select the rapeseed germplasm with superior advantages as green manure. According to the comprehensive analysis of N efficiency and tolerance index of different rapeseed germplasms at full-bloom stage, 25 of 73 rapeseed germplasms had relatively strong tolerance to low N, while 17 germplasms had relatively poor tolerance to low N, belonging to low N sensitive type. Further analysis revealed that the fresh weight per plant, N accumulation, and N uptake efficiency of low N tolerance germplasms were significantly greater than those of low N sensitive germplasms under two N treatments, it could be used as potential green manure for further application. According to the calculation, the maximum amount of N returned to the field in the low N tolerance rapeseed germplasm was 80.2 kg hm^-2. Above all, the selected germplasms with great low N tolerance could be used as potential green manure rapeseed resources to be reserved and applied. In actual production, to better realize the industrial application goal of “the few fertilizers convert into the more green manure”, the application of low N tolerant rapeseed as green fertilizer can reduce the input of chemical fertilizer.

Linkage disequilibrium and population structure in a core collection of Brassica napus (L.).

Estimation of genetic diversity in rapeseed is important for sustainable breeding program to provide an option for the development of new breeding lines. The objective of this study was to elucidate the patterns of genetic diversity within and among different structural groups, and measure the extent of linkage disequilibrium (LD) of 383 globally distributed rapeseed germplasm using 8,502 single nucleotide polymorphism (SNP) markers. We divided the germplasm collection into five subpopulations (P1 to P5) according to geographic and growth habit-related patterns. All subpopulations showed moderate genetic diversity (average H = 0.22 and I = 0.34). The pairwise Fst comparison revealed a great degree of divergence (Fst > 0.24) between most of the combinations. The rutabaga type showed highest divergence with spring and winter types. Higher divergence was also found between winter and spring types. Admixture model based structure analysis, principal component and neighbor-joining tree analysis placed all subpopulations into three distinct clusters. Admixed genotype constituted 29.24% of total genotypes, while remaining 70.76% belongs to identified clusters. Overall, mean linkage disequilibrium was 0.03 and it decayed to its half maximum within < 45 kb distance for whole genome. The LD decay was slower in C genome (< 93 kb); relative to the A genome (< 21 kb) which was confirmed by availability of larger haplotype blocks in C genome than A genome. The findings regarding LD pattern and population structure will help to utilize the collection as an important resource for association mapping efforts to identify genes useful in crop improvement as well as for selection of parents for hybrid breeding.

Synergistic/antagonistic interactions between Neopseudocercosporella, Alternaria, Leptosphaeria, and Hyaloperonospora determine aggregate foliar disease severity in rapeseed

AbstractWhite leaf spot (Neopseudocercosporella capsellae), Alternaria leaf spot (Alternaria brassicae), blackleg (Leptosphaeria maculans), and downy mildew (Hyaloperonospora brassicae) commonly co‐occur on rapeseed (Brassica napus). In controlled environment studies, the synergistic/antagonistic interactions between these four pathogens were determined using two cultivars (Surpass 400, Thunder TT) with contrasting susceptibilities/resistances towards these pathogens. A spectrum of significant (p &lt; 0.001) contrasting synergistic/antagonistic interactions between the four pathogens was observed and specific pathogen–pathogen interaction outcomes were determined by sequence of inoculation of different pathogens on each cultivar. On Thunder TT, Alternaria leaf spot was more severe (p &lt; 0.001) when A. brassicae was applied prior to N. capsellae, but was reduced (p &lt; 0.001) when A. brassicae was applied following N. capsellae. On Surpass 400, Alternaria leaf spot was enhanced (p &lt; 0.001) when A. brassicae was applied following N. capsellae. For interactions involving H. brassicae on Thunder TT, downy mildew was reduced (p &lt; 0.001) when co‐inoculated with N. capsellae, A. brassicae, or L. maculans, irrespective of co‐inoculating pathogen application sequence. This study highlights how disease severity of one or more co‐occurring pathogens is enhanced/decreased in the presence of other co‐occurring pathogens and emphasizes the importance of both pathogen inoculation sequence and relative host plant resistances/susceptibilities to different pathogens in together determining the total disease burden from these co‐occurring rapeseed diseases. Clearly, there is a need for rapeseed germplasm selection and breeding programmes to seriously consider the implications of co‐occurring pathogen complexes rather than solely relying upon single‐pathogen screening tests.

Genetic segregation analysis of unsaturated fatty acids content in the filial generations of high-linolenic-acid rapeseed (Brassica napus)

Alpha linolenic acid (ALA) is an essential polyunsaturated fatty acids that can improve human health. Rapeseed is the second largest oil crop in the world but the ALA content in its seed fatty acids is only about 10%. Two rapeseed germplasms YH25005 and R8Q10 with high content (up to 21%) ALA were developed by intervarietal crossing. They were used as the maternal parent (P1) when crossed with a low ALA parent SW (P2) to produce the seeds of the F1 hybrid, F2, and backcrosses to P1 (BCP1) and P2 (BCP2). A multigeneration joint segregation analysis was conducted to determine major gene ​+ ​polygene effects of the content of three major unsaturated fatty acids including oleic (OA), linoleic (LA) and ALA. The results showed that, although some genes favorable to ALA accumulation were not allelic in R8Q10 and YH25005, all the inheritances of OA, LA and ALA in YH25005 ​× ​SW and R8Q10 ​× ​SW followed a genetic model of ‘two pairs of additive major genes ​+ ​additive-dominant polygenes’. It is suggested that the contents of OA, LA and ALA are closely related and the major genes in the parent SW containing loss-of-function mutations in FAD2 and FAD3 loci had strong effect to reduce ALA and elevate OA. However, total genetic effect of the polygenes was greater than that of the two major genes, especial on ALA content. It indicated that it is necessary to employ a larger F2 population to find the plant that accumulate enough minor-effect polygenes for high ALA content. The results are useful for high ALA rapeseed breeding and future work of gene mapping.

Transcriptome analysis reveals gene responses to herbicide, tribenuron methyl, in Brassica napus L. during seed germination

BackgroundTribenuron methyl (TBM) is an herbicide that inhibits sulfonylurea acetolactate synthase (ALS) and is one of the most widely used broad-leaved herbicides for crop production. However, soil residues or drifting of the herbicide spray might affect the germination and growth of rapeseed, Brassica napus, so it is imperative to understand the response mechanism of rape to TBM during germination. The aim of this study was to use transcriptome analysis to reveal the gene responses in herbicide-tolerant rapeseed to TBM stress during seed germination.Results2414, 2286, and 1068 differentially expressed genes (DEGs) were identified in TBM-treated resistant vs sensitive lines, treated vs. control sensitive lines, treated vs. control resistant lines, respectively. GO analysis showed that most DEGs were annotated to the oxidation-reduction pathways and catalytic activity. KEGG enrichment was mainly involved in plant-pathogen interactions, α-linolenic acid metabolism, glucosinolate biosynthesis, and phenylpropanoid biosynthesis. Based on GO and KEGG enrichment, a total of 137 target genes were identified, including genes involved in biotransferase activity, response to antioxidant stress and lipid metabolism. Biotransferase genes, CYP450, ABC and GST, detoxify herbicide molecules through physical or biochemical processes. Antioxidant genes, RBOH, WRKY, CDPK, MAPK, CAT, and POD regulate plant tolerance by transmitting ROS signals and triggering antioxidant enzyme expression. Lipid-related genes and hormone-related genes were also found, such as LOX3, ADH1, JAZ6, BIN2 and ERF, and they also played an important role in herbicide resistance.ConclusionsThis study provides insights for selecting TBM-tolerant rapeseed germplasm and exploring the molecular mechanism of TBM tolerance during germination.

BnaGVD: A genomic variation database of rapeseed (Brassica napus).

Rapeseed (Brassica napus L.) is a typical polyploid crop and one of the most important oilseed crops worldwide. With the rapid progress on high-throughput sequencing technologies and the reduction of sequencing cost, large-scale genomic data of a specific crop have become available. However, raw sequence data are mostly deposited in the sequence read archive of the National Center of Biotechnology Information (NCBI) and the European Nucleotide Archive (ENA), which is freely accessible to all researchers. Extensive tools for practical purposes should be developed to efficiently utilize these large raw data. Here, we report a web-based rapeseed genomic variation database (BnaGVD, http://rapeseed.biocloud.net/home) from which genomic variations, such as single nucleotide polymorphisms (SNPs) and insertions/deletions (InDels) across a world-wide collection of rapeseed accessions, can be referred. The current release of the BnaGVD contains 34,591,899 high-quality SNPs and 12,281,923 high-quality InDels and provides search tools to retrieve genomic variations and gene annotations across 1,007 accessions of worldwide rapeseed germplasm. We implement a variety of built-in tools (e.g., BnaGWAS, BnaPCA, and BnaStructure) to help users perform in-depth analyses. We recommend this web resource for accelerating studies on the functional genomics and screening of molecular markers for rapeseed breeding.

Identification and evaluation of high nitrogen nutrition efficiency in rapeseed (Brassica napus L.) germplasm

To establish identification and evaluation methods of N (nitrogen) absorption and utilization of rapeseed (Brassica napus L.), difference of N nutrition efficiency (NNE) among rapeseed germplasms and relationship between NNE and plant traits under various N application rates were analyzed in this research. Pot cultivating experiments were conducted to investigate NNE with 3 ​N application rates in soil (0.05, 0.2 and 0.3 ​g/kg). A total of 12 rapeseed germplasms were planted, nitrogen absorption efficiency (NAE) and nitrogen utilization efficiency (NUE) in seedling stage, bolting stage, initial flowering stage, final flowering stage, and maturity stage were obtained. Results showed that bolting stage was the best period for NAE identification and evaluation. Low N application rate in soil (0.05 ​g/kg) was the best for NAE, and the indirect indexes were basal stem diameter, plant root dry weight and above ground plant dry weight. Maturity stage was the best period for NUE identification and evaluation. High N application rate in soil (0.3 ​g/kg) was the best for NUE, and indirect indexes were above ground plant dry weight and basal stem diameter. N application rates of 0.05 ​g/kg in soil was the best for nitrogen harvest index at maturity stage, and indirect indexes was number of pods per plant. Plant traits of rapeseed germplasms affected NNE. Higher basal stem diameter, plant root dry weight and above ground plant dry weight at bolting stage under low N application rate were important characteristics of N absorption in rapeseed. Higher above ground plant dry weight and basal stem diameter at maturity stage under high N application rate were important characteristics of N utilization. Higher number of pods per plant at maturity stage under lowe N application rate was an important characteristic of N harvest index. These results provided a reliable index for N management and provided theoretical basis for guiding rapeseed breeding.

WITHDRAWN: Identification and evaluation method of high nitrogen nutrition efficiency in rapeseed (Brassica napus L.) germplasms

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.ocsci.2020.07.004 . The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

Comparative Study of Fatty Acid Composition, Total Phenolics, and Antioxidant Capacity in Rapeseed Mutant Lines

AbstractThere is limited variability within rapeseed germplasm in Morocco. Induced mutation was recently used to generate novel genetic variability and develop mutant lines combining desirable traits. In this context, nine promising advanced rapeseed M2 mutant lines and the wild‐type variety “INRA‐CZH2” were evaluated for their seed oil content, fatty acid composition, total phenolic content (TPC), and free‐radical scavenging activity (FRSA) by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) and 3‐ethylbenzothiazoline‐6‐sulfonic acid (ABTS) methods. The results showed significant variability among all mutants in seed oil content (38.14–42.04%) and fatty acids (SAFA = 5.49–10.99%, MUFA = 50.33–71.62%, PUFA = 22.89–8.68%). The mutant H2M‐5 exhibited the highest fraction of MUFA and the lowest proportion of SAFA and PUFA, while the mutant H2M‐4 showed the highest SAFA and PUFA amounts and the lowest MUFA level. TPC varied from 2.16 to 4.35 mg GAE/100 g. The highest amount was found in the mutant H2M‐1, which is about twice that of other mutants and the wild‐type variety. FRSA differed significantly among the samples, and the variations observed for DPPH and ABTS methods were 40.5–59.28% and 40.31–59.86%, respectively. FRSA was positively correlated to TPC in the sampled oils (r = 0.801 and 0.802, P &lt; 0.01). This is the first report emphasizing the biochemical potential of rapeseed varieties and novel mutants in Morocco. H2M‐1, H2M‐4, and H2M‐5 were proposed for the Rapeseed National Breeding Program, as they showed higher levels in some biochemical traits of interest.

BnaSNPDB: An interactive web portal for the efficient retrieval and analysis of SNPs among 1,007 rapeseed accessions

The rapid development of high-throughput sequencing technology and the decrease in sequencing costs provide valuable resources and great opportunities for researchers to investigate genomic variations across hundreds or even thousands of accessions in the post-genomic era. The management and exploration of these large-scale genomic variations heavily rely on programming and command-line environments, which are challenging and time-consuming for most experimental biologists and plant breeders. Here, we present BnaSNPDB, an interactive web portal with a user-friendly interface that provides multiple analysis modules for retrieving, analyzing, and visualizing single nucleotide polymorphisms among 1,007 accessions of worldwide rapeseed germplasm. It is compatible, extendable, and portable to be easily set up on different operating systems, and can be accessed at http://121.41.229.126:3838/bnasnpdb and http://rapeseed.zju.edu.cn:3838/bnasnpdb. Its whole dataset and code are available at https://github.com/YTLogos/BnaSNPDB. This database is essential for accelerating studies on the functional genomics and screening of the molecular markers of molecular-assisted breeding in rapeseed.

A systematic dissection of the mechanisms underlying the natural variation of silique number in rapeseed (Brassica napus L.) germplasm.

SummarySilique number is the most important component of yield in rapeseed (Brassica napus L.). To dissect the mechanism underlying the natural variation of silique number in rapeseed germplasm, a series of studies were performed. A panel of 331 core lines was employed to genome‐wide association study (GWAS), and 27 loci (including 20 novel loci) were identified. The silique number difference between the more‐ and fewer‐silique lines can be attributed to the accumulative differences in flower number and silique setting rate. Each of them accounted for 75.2% and 24.8%, respectively. The silique number was highly associated with the total photosynthesis and biomass. Microscopic analysis showed that the difference between extremely more‐ and fewer‐silique lines normally occurred at the amount of flower bud but not morphology. Transcriptome analysis of shoot apical meristem (SAM) suggested that most of enriched groups were associated with the auxin biosynthesis/metabolism, vegetative growth and nutrition/energy accumulation. By integrating GWAS and RNA‐seq results, six promising candidate genes were identified, and some of them were related to biomass accumulation. In conclusion, the natural variation of silique number is largely affected by the biomass and nutrition accumulation, which essentially reflects the positive regulatory relationship between the source and sink. Our study provides a comprehensive and systematic explanation for natural variation of silique number in rapeseed, which provides a foundation for its improvement.