Heterogeneous expression of stearoyl-acyl carrier protein desaturase genes SAD1 and SAD2 from Linum usitatissimum enhances seed oleic acid accumulation and seedling cold and drought tolerance in Brassica napus

Flax(Linum usitatissimum L.)is a versatile crop and its seeds are a major source of unsaturated fatty acids.Stearoyl-acyl carrier protein desaturase(SAD)is a dehydrogenase enzyme that plays a key role in oleic acid biosynthesis as well as responses to biotic and abiotic stresses.However,the function of SAD orthologs from L.usitatissimum has not been assessed.Here,we found that two LuSAD genes,LuSAD1 and LuSAD2,are present in the genome of L.usitatissimum cultivar‘Longya 10’.Heterogeneous expression of either LuSAD1 or LuSAD2 in Arabidopsis thaliana resulted in higher contents of total fatty acids and oleic acid in the seeds.Interestingly,ectopic expression of LuSAD2 in A.thaliana caused altered plant architecture.Similarly,the overexpression of either LuSAD1 or LuSAD2 in Brassica napus also resulted in increased contents of total fatty acids and oleic acid in the seeds.Furthermore,we demonstrated that either LuSAD1 or LuSAD2 enhances seedling resistance to cold and drought stresses by improving antioxidant enzyme activity and nonenzymatic antioxidant levels,as well as reducing membrane damage.These findings not only broaden our knowledge of the LuSAD functions in plants,but also offer promising targets for improving the quantity and quality of oil,and the abiotic stress tolerance of oil-producing crops,through molecular manipulation.

BnaC03.BIN2 regulates plant height by affecting the main inflorescence length and first effective branch height in Brassica napus L.

Rapeseed(Brassica napus L.)is one of the main oil crops in the world,and increasing its yield is of great significance for ensuring the safety of edible oil.Presently,improving rapeseed plant architecture is an effective way to increase rapeseed yield with higher planting density.However,the regulatory mechanism of rapeseed plant architecture is poorly understood.In this study,a dwarf rapeseed mutant dwarf08(df08)is obtained by ethyl methane sulfonate(EMS)-mutagenesis.The decrease in plant height of df08 is mainly caused by the reduction in main inflorescence length and first effective branch height and controlled by a single semi-dominant gene.The hybrid plants(F1)show a semi-dwarf phenotype.Through map-based cloning and transgenic assay,we confirm that the nonsynonymous single nucleotide variant(SNV)(C to T)in BnaC03.BIN2,which is homologous with Arabidopsis(Arabidopsis thaliana)BIN2,is responsible for the dwarfism of df08.BnaC03.BIN2 interacts with BnaBZR1/BES1 and involves in brassinosteroids(BRs)signal transduction.Proline to Leucine substitution in 284(P284L)enhances the protein stability of BnaC03.bin2-D,disrupts BRs signal transduction and affects the expression of genes regulating cell division,leading to dwarfism of df08.This study provides a new insight for the mechanism of rapeseed plant height regulation and creates an elite germplasm that can be used for genetic improvement of rapeseed architecture.

Utilizing resequencing big data to facilitate Brassica vegetable breeding:tracing introgression pedigree and developing highly specific markers for clubroot resistance

Clubroot caused by Plasmodiophora brassicae is a devastating disease of Cruciferous crops.Developing cultivars with clubroot resistance(CR)is the most effective control measure.For the two major Brassica vegetable species B.rapa and B.oleracea,several commercial cultivars with unclear CR pedigrees have been intensively used as CR donors in breeding.However,the continuous occurrence of CR-breaking makes the CR pedigree underlying these cultivars one of the breeders'most urgent concerns.The complex intraspecific diversity of these two major Brassica vegetables has also limited the applicability of CR markers in different breeding programs.Here we first traced the pedigree underlying two kinds of CR that have been widely applied in breeding by linkage and introgression analyses based on public resequencing data.In B.rapa,a major locus CRzi8 underlying the CR of the commercial CR donor‘DegaoCR117’was identified.CRzi8 was further shown to have been introgressed from turnip(B.rapa ssp.rapifera)and that it carried a potential functional allele of Crr1a.The turnip introgression carried CRb^(c),sharing the same coding sequence with the CRb that was also identified from chromosome C07 of B.oleracea CR cultivars with different morphotypes.Within natural populations,variation analysis of linkage intervals of CRzi8,PbBa8.1,CRb,and CRb^(c)yielded easily resolved InDel markers(>20 bp)for these fundamental CR genes.The specificity of these markers was tested in diverse cultivars panels,and each exhibited high reliability in breeding.Our research demonstrates the value of the practice of applying resequencing big data to solve urgent concerns in breeding programs.

Molecular mechanism of flowering time regulation in Brassica rapa:similarities and differences with Arabidopsis

Properly regulated flowering time is pivotal for successful plant reproduction.The floral transition from vegetative growth to reproductive growth is regulated by a complex gene regulatory network that integrates environmental signals and internal conditions to ensure that flowering takes place under favorable conditions.Brassica rapa is a diploid Cruciferae species that includes several varieties that are cultivated as vegetable or oil crops.Flowering time is one of the most important agricultural traits of B.rapa crops because of its influence on yield and quality.The transition to flowering in B.rapa is regulated by several environmental and developmental cues,which are perceived by several signaling pathways,including the vernalization pathway,the autonomous pathway,the circadian clock,the thermosensory pathway,and gibberellin(GA)signaling.These signals are integrated to control the expression of floral integrators BrFTs and BrSOC1s to regulate flowering.In this review,we summarized current research advances on the molecular mechanisms that govern flowering time regulation in B.rapa and compare this to what is known in Arabidopsis.

Turnip mosaic virus pathogenesis and host resistance mechanisms in Brassica

Turnip mosaic virus(TuMV)is a devastating potyvirus pathogen that infects a wide variety of both cultivated and wild Brassicaceae plants.We urgently need more information and understanding of TuMV pathogenesis and the host responses involved in disease development in cruciferous crops.TuMV displays great versatility in viral pathogenesis,especially in its replication and intercellular movement.Moreover,in the coevolutionary arms races between TuMV and its hosts,the virus has evolved to co-opt host factors to facilitate its infection and counter host defense responses.This review mainly focuses on recent advances in understanding the viral factors that contribute to the TuMV infection cycle and the host resistance mechanism in Brassica.Finally,we propose some future research directions on TuMV pathogenesis and control strategies to design durable TuMV-resistant Brassica crops.

BnaWRKY75 positively regulates the resistance against Sclerotinia sclerotiorum in ornamental Brassica napus

With the development of tourism at home and abroad,Rapeseed(Brassica napus)has become an important ornamental plant.However,its ornamental value at the inflorescence stage is greatly reduced by Sclerotinia sclerotiorum.Identification of important genes in the defense responses is critical for molecular breeding,which is an important strategy for controlling the disease.In this study,we isolated a B.napus WRKY transcription factor gene,BnaWRKY75.BnaWRKY75 was found to encode a nucleus-localized protein and exhibited relatively high expression in the stems.Arabidopsis thaliana transgenic plants expressing BnaWRKY75 showed enhanced resistance to S.sclerotiorum,and both ProBnaWRKY75:GUS and gene expression analyses showed that BnaWRKY75 was highly responsive to S.sclerotiorum infection,indicating the involvement of BnaWRKY75 in response to this infection.Furthermore,overexpression(OE)of BnaWRKY75 in B.napus significantly enhanced the resistance to S.sclerotiorum,whereas the resistance was reduced in RNAi transgenic B.napus plants.Moreover,the BnaWRKY75-OE B.napus plants exhibited constitutive activation of salicylic acid-,jasmonic acid-,and ethylene-mediated defense responses and the inhibition of both H_(2)O_(2)and O_(2)·^(-)accumulation in response to this pathogen.By contrast,BnaWRKY75-RNAi plants showed a reverse pattern,suggesting that BnaWRKY75 is involved in hormonal signaling pathways and in the control of reactive oxygen species accumulation.In conclusion,these data indicate that BnaWRKY75,a regulator of multiple defense responses,positively regulates resistance against S.sclerotiorum,which may guide the improvement of resistance in rapeseed.

Improved genome annotation of Brassica oleracea highlights the importance of alternative splicing

Brassica oleracea has been developed into many important crops,including cabbage,kale,cauliflower,broccoli and so on.The genome and gene annotation of cabbage(cultivar JZS),a representative morphotype of B.oleracea,has been widely used as a common reference in biological research.Although its genome assembly has been updated twice,the current gene annotation still lacks information on untranslated regions(UTRs)and alternative splicing(AS).Here,we constructed a high-quality gene annotation(JZSv3)using a full-length transcriptome acquired by nanopore sequencing,yielding a total of 59452 genes and 75684 transcripts.Additionally,we re-analyzed the previously reported transcriptome data related to the development of different tissues and cold response using JZSv3 as a reference,and found that 3843 out of 11908 differentially expressed genes(DEGs)underwent AS during the development of different tissues and 309 out of 903 cold-related genes underwent AS in response to cold stress.Meanwhile,we also identified many AS genes,including BolLHCB5 and BolHSP70,that displayed distinct expression patterns within variant transcripts of the same gene,highlighting the importance of JZSv3 as a pivotal reference for AS analysis.Overall,JZSv3 provides a valuable resource for exploring gene function,especially for obtaining a deeper understanding of AS regulation mechanisms.

Knock-out of BnHva22c reduces the susceptibility of Brassica napus to infection with the fungal pathogen Verticillium longisporum

Verticillium longisporum(Vl43)is a soilborne hemibiotrophic fungal pathogen causing stem striping on oilseed rape(OSR)and severe yield losses.Breeding for resistant varieties is the most promising approach to control this disease.Here,we report the identification of Hva22c as a novel susceptibility factor and its potential for improving OSR resistance.Hva22c is a member of the Hva22 gene family,originally described for barley(Hordeum vulgare).Several Hva22 members have been located at the endoplasmic reticulum.Hva22c is up-regulated in response to Vl43 in both Arabidopsis and OSR.We demonstrate that knock-out of Hva22c in OSR by CRISPR/Cas9 and its homolog in Arabidopsis by T-DNA insertion reduced plants’susceptibility to Vl43 infection and impaired the development of disease symptoms.To understand the underlying mechanism,we analysed transcriptomic data from infected and non-infected roots of hva22c knock-out and wild type plants.We identified a homozygous mutant with frame-shifts in all four BnHva22c loci displaying a vastly altered transcriptional landscape at 6 dpi.Significantly,a large set of genes was suppressed under mock conditions including genes related to the endomembrane systems.Among the up-regulated genes we found several defense-related and phytohormone-responsive genes when comparing mutant to the wild type.These results demonstrate that Hva22c is functionally required for a fully compatible plant-fungus interaction.Its loss of function reduces plant susceptibility,most likely due to endoplasmatic reticulum and Golgi dysfunction accompanied by additionally activated defense responses.These findings can help improve OSR resistance to V.longisporum infection.

Landscape of Sequence Variations in Homologous Copies of FAD2 and FAD3 in Rapeseed(Brassica napus L.)Germplasm with High/Low Linolenic Acid Trait

Genetic manipulation(either restraint or enhancement)of the biosynthesis pathway ofα-linolenic acid(ALA)in seed oil is an important goal in Brassica napus breeding.B.napus is a tetraploid plant whose genome often har-bors four and six homologous copies,respectively,of the two fatty acid desaturases FAD2 and FAD3,which con-trol the last two steps of ALA biosynthesis during seed oil accumulation.In this study,we compared their promoters,coding sequences,and expression levels in three high-ALA inbred lines 2006L,R8Q10,and YH25005,a low-ALA line A28,a low-ALA/high-oleic-acid accession SW,and the wildtype ZS11.The expression levels of most FAD2 and FAD3 homologs in the three high-ALA accessions were higher than those in ZS11 and much higher than those in A28 and SW.The three high-ALA accessions shared similar sequences with the pro-moters and CDSs of BnFAD3.C4 and BnFAD3.A3.In A28 and SW,substitution of three amino acid residues in BnFAD2.A5 and BnFAD2.C5,an absence of BnFAD2.C1 locus,and a 549 bp long deletion on the BnFAD3.A3 promoter were detected.The profile of BnFAD2 mutation in the two low-ALA accessions A28 and SW is different from that reported in previous studies.The mutations in BnFAD3 in the high-ALA accessions are reported for thefirst time.In identifying the sites of these mutations,we provide detailed information to aid the design of mole-cular markers for accelerated breeding schemes.

Editing of eIF(iso)4E.c confers resistance against Turnip mosaic virus in Brassica rapa

Turnip mosaic virus(TuMV)constitutes one of the primary diseases affecting Brassica rapa,severely impacting its production and resulting in crop failures in various regions worldwide.Recent research has demonstrated the significance of plant translation initiation factors,specifically the eIF4E and eIF4G family genes,as essential recessive disease resistance genes.In our study,we conducted evolutionary and gene expression studies,leading us to identify e IF(iso)4E.c as a potential TuMV-resistant gene.Leveraging CRISPR/Cas9 technology,we obtained mutant B.rapa plants with edited eIF(iso)4E.c gene.We confirmed eIF(iso)4E.c confers resistance against TuMV through phenotypic observations and virus content evaluations.Furthermore,we employed ribosome profiling assays on eif(iso)4e.c mutant seedlings to unravel the translation landscape in response to TuMV.Interestingly,we observed a moderate correlation between the fold changes in gene expression at the transcriptional and translational levels(R^(2)=0.729).Comparative analysis of ribosome profiling and RNA-seq data revealed that plant-pathogen interaction,and MAPK signaling pathway-plant pathways were involved in eIF(iso)4E.c-mediated TuMV resistance.Further analysis revealed that sequence features,coding sequence length,and normalized minimal free energy,influenced the translation efficiency of genes.Our study highlights that the loss of e IF(iso)4E.c can result in a highly intricate translation mechanism,acting synergistically with transcription to confer resistance against TuMV.

The influence of Lactobacillus plantarum fermentation in selenium-enriched Brassica napus L.:changes in the nutritional constituents,bioactivities and bioaccessibility

Selenium(Se)-enriched Brassica napus L.is a valuable organic Se supplement.In this study,the fermentation broth enriched with organic Se(FFS)was prepared using Lactobacillus plantarum to ferment the substrate of Se-enriched Brassica napus L.Significant increases were observed after fermentation in total sugars,reducing sugars,soluble proteins,total phenolic content(TPC),and total flavonoid content(TFC).The organic Se was retained at a concentration of 54.75 mg/g in the freeze-dried sample.Principal component analysis and cluster analysis showed good separation between the FFS and unfermented(FS)groups.Fragrant 2-ethyloxetane had the highest content among all volatiles,while sinapine had the highest content among all phenolic compounds.The fermentation process showed remarkable improvement in the abundance and concentration of volatile compounds and phenolic contents,making FFS exhibit strong antioxidant activity and inhibitory capacity againstα-glucosidase activity.The bioaccessibility of phenolic compounds was significantly greater in FFS compared to FS.ADMET analysis revealed that the majority of phenolic compounds contained in FFS did not exhibit mutagenicity toxicity,hepatotoxicity,skin sensitization,or blood-brain barrier penetration,indicating a favorable level of biosafety.Overall,our study provides a new insight into the further utilization of Se-enriched Brassica napus L.in foods.

Effect of Foliar Fertilizer Spraying at Seedling Stage on the Growth Physiological Characteristics and Yield of Brassica napus L.

In order to select a suitable foliar fertilizer for Brassica napus L.at the seedling stage,using‘Fengyou 958’as the material,different foliar fertilizers including BR,Se,Si,BR+Si,BR+Se,Se+Si and BR+Se+Si were sprayed at the seedling stage to study their effect on the physiological characteristics,growth and yield of Brassica napus L..The results showed that the growth,chlorophyll content,soluble sugar content,soluble protein content,and yield of different treatments at the budding stage improved compared with the control.The effect of the Si+Se treatment was the best,followed by the Se and Si treatments.The chlorophyll content of the flower decreased continuously during the whole flowering period,and the chlorophyll content of the mature silique peel was higher than that of the seed.The content of soluble sugar in flowers was the highest in the early flowering stage,and the content of soluble sugar in leaves at the flowering stage was higher than that at the budding stage.The soluble sugar content in the harvested silique peel decreased gradually with the increase of time,and that in the silique peel and seed was similar at 35 d after pollination.The soluble protein content in the silique peel and seed decreased gradually at the mature stage,and the soluble protein content in the silique peel was higher than that in the seed at the same stage.Si+Se foliar fertilizer spraying at the seedling stage can promote the growth and yield of Brassica napus L.and can be applied in Brassica napus L.production.

Development of a KASP Marker on Chromosome A05 for Seed Oil Content of Brassica napus

In order to identify the molecular markers that can be widely used in the breeding of Brassica napus L.varieties with high seed oil content under different genetic backgrounds,we developed a Kompetitive Allele Specific PCR(KASP)marker for seed oil content on the basis of the results from available studies.The verification in the F_(2) population showed that the marker was closely linked to the quantitative trait locus(QTL)for oil content on chromosome A05.The findings helped to breed the‘Fengyou’varieties with high seed oil content in the middle reaches of the Yangtze River.

油菜(Brassica napus)β-1,4-木糖基转移酶基因BnIRX14克隆、序列分析及亚细胞定位

糖基转移酶(Glycosyltransferase,GTs)广泛参与植物次生物质的代谢及生物和非生物胁迫,β-1,4-木糖基转移酶属于糖基转移酶GT43家族成员。为了探究油菜β-1,4-木糖基转移酶对油菜次生物质的代谢和逆境调控,利用5′RACE和3′RACE方法从甘蓝型油菜中扩增获得油菜β-1,4-木糖基转移酶基因BnIRX14全长cDNA,该cDNA具有1566 bp的完整开放阅读框,编码522个氨基酸,分子质量约58.92 ku,由8315个原子组成,分子式为C_(2631)H_(4168)N_(742)O_(753)S_(21),具有多个磷酸化位点和糖基化修饰位点,属非分泌性单次跨膜蛋白。结构域分析表明,BnIRX14具有GTs家族保守的DxD保守结构域和UGT糖基转移酶PSPG特征结构域,属于糖基转移酶GT43家族成员。BiFC亚细胞定位初步显示BnIRX14定位于细胞质中,蛋白互作预测表明BnIRX14与各类糖合成和转运蛋白高度互作。结构域预测和互作分析初步表明,BnIRX14属于油菜糖基转移酶GT43家族成员,可能通过与糖合成和转运相关蛋白互作参与油菜木糖的合成代谢进而参与生长发育及逆境响应。

Dissecting the genetic architecture of glucosinolate compounds for quality improvement in flowering stalk tissues of Brassica napus

Glucosinolates(GSLs) and their hydrolytic products contribute to the quality traits of rapeseed flowering stalk tissues, such as taste, flavor and anticarcinogenic properties(Glucoraphanin). However, little is known about the genetic mechanisms of GSL accumulation in rapeseed flowering stalks. In this study, the variation and genetic architecture of GSL metabolites in flowering stalk tissues were investigated for the first time among a panel of 107 accessions. All GSL compounds exhibited continuous and wide variations in the present population. Progoitrin,glucobrassicanapin and gluconapin were the most abundant GSL compounds. Five quantitative trait loci(QTL) significantly associated with three GSL compounds were identified by genome-wide association study. GRA_C04 was under selected during modern breeding, in which the ratio of lower GSL haplotype(HAP2) in the accessions bred before 1990(52.56%) was significantly lower than that after 1990(78.95%). Four candidate genes, BnaA01. SOT16, BnaA06. SOT17, Bna A06. MYB51a, and Bna A06. MYB51b, were identified in the GTL_A01 and 4OH_A06 regions.These findings provide new insights into GSL biosynthesis in flowering stalk tissues and facilitate quality improvement in rapeseed flowering stalks.

BnaUBP15s positively regulates seed size and seed weight in Brassica napus

Brassica napus(B.napus)is a globally significant oilseed crop,making a substantial contribution to both human oil and livestock feed production.Enhancing seed weight is crucial for improving rapeseed yield;however,only a limited number of seed weight-related genes have been functionally validated in B.napus thus far.UBIQUITINSPECIFIC PROTEASE 15(UBP15)belongs to the ubiquitin protease pathway and plays a maternal role in prolonging seed development in Arabidopsis.The potential utilization of UBP15 for enhancing seed yield in B.napus has remained unexplored until now.In this study,we identified the orthologs of UBP15 in B.napus and investigated its functionality using the CRISPR-Cas9 system.We generated mutant plants with multiple editing types targeting Bnaubp15s and successfully isolated T-DNA-free homozygous mutant lines that exhibited edits across four homologs of BnaUBP15 in T2 generation plants.Our preliminary data demonstrated that mutation of BnaUBP15s significantly reduced seed size,seed weight,and plant height while noticeably increasing the number of primary branches.These findings not only provide crucial evidence for further elucidating the molecular mechanism underlying the regulation of seed weight and size by BnaUBP15s but also offer promising novel germplasm for enhancing plant architecture.

First report of Leptosphaeria sclerotioides on Brassica napus in Northwestern China

In 2020,diseased seedlings of winter oilseed rape(Brassica napus)with cankered taproots as well as abundant sclerotium-like structures in the soil surrounding the roots were found in Longxi County of Gansu province of northwestern China.A fungus with production of pycnidia was isolated from the diseased roots,and it was identified based on morphological characteristics,molecular phylogeny(ITS,LSU)and PCR detection with the specific primers.The fungus was identified as Leptosphaeria sclerotioides Gruyter,Aveskamp&Verkley[anamorph:Phoma sclerotioides(Preuss)ex Sacc.].Re-inoculation of isolates of P9 and P10 of L.sclerotioides on winter oilseed rape(B.napus cultivar‘Zhongshuang No.9’)in Wuhan caused formation of abundant sclerotium-like structures in soil surrounding the roots,but failed to produce root cankers as those observed in Gansu possibly due to lack of long peroid of low-temperature conditioning in Wuhan.In spite of this,plant height,pod number and seed yield of oilseed rape were significantly reduced in the treatment with L.sclerotioides P9 and P10,compared to the control treatment.To the best of our knowledge,this is the first report of L.sclerotioides on B.napus in China and the finding broadened our understanding about the natural distribution of this psychrophilic fungus.

BnbHLH92a negatively regulates anthocyanin and proanthocyanidin biosynthesis in Brassica napus

Yellow seed trait is a desirable characteristic with potential for increasing seed quality and commercial value in rapeseed,and anthocyanin and proanthocyanidins(PAs)are major seed-coat pigments.Few transcription factors involved in the regulation of anthocyanin and PAs biosynthesis have been characterized in rapeseed.In this study,we identified a transcription factor gene BnbHLH92a(BnaA06T0441000ZS)in rapeseed.Overexpressing BnbHLH92a both in Arabidopsis and in rapeseed reduced levels of anthocyanin and PAs.Correspondingly,the expression profiles of anthocyanin and PA biosynthesis genes(TT3,BAN,TT8,TT18,and TTG1)were shown by quantitative real-time PCR to be inhibited in BnbHLH92a-overexpressing Arabidopsis seeds,indicating that BnbHLH92a represses the anthocyanin and PA biosynthesis pathway in Arabidopsis.BnbHLH92a physically interacts with the BnTTG1 protein and represses the biosynthesis of anthocyanins and PAs in rapeseed.BnbHLH92a also binds directly to the BnTT18 promoter and represses its expression.These results suggest that BnbHLH92a is a novel upstream regulator of flavonoid biosynthesis in B.napus.

Genome-wide recombination variation in biparental segregating and reciprocal backcross populations provides information for introgression breeding in Brassica napus

Variation in patterns of recombination in plant genomes provides information about species evolution,genetic diversity and crop improvement. We investigated meiotic crossovers generated in biparental segregating and reciprocal backcross populations of the allopolyploid genome of rapeseed(Brassica napus)(AACC, 2n = 38). A structured set of 1445 intercrossed lines was derived from two homozygous de novo genome-assembled parents that represented the major genetic clusters of semi-winter Chinese and winter European rapeseeds, and was used to increase QTL resolution and achieve genomic reciprocal introgression. A high-density genetic map constructed with 6161 genetic bins and anchored centromere regions was used to establish the pattern of recombination variation in each chromosome. Around 93%of the genome contained crossovers at a mean rate of 3.8 c M Mb^(-1), with the remaining 7% attributed to centromeres or low marker density. Recombination hotspots predominated in the A genome, including two-thirds of those associated with breeding introgression from B. rapa. Genetic background might affect recombination variation. Introgression of genetic diversity from European winter to Chinese semi-winter rapeseed showed an increase in crossover rate under the semi-winter environment. Evidence for an elevated recombination rate having historically contributed to selective trait improvement includes accumulation of favorable alleles for seed oil content on hotspots of chromosome A10. Conversely, strong artificial selection may affect recombination rate variation, as appears to be the case with a coldspot resulting from strong selection for glucosinolate alleles on A09. But the cold region would be promptly reactivated by crossing design indicated by the pedigree analysis. Knowledge of recombination hotspots and coldspots associated with QTL for 22 traits can guide selection strategies for introgression breeding between the two gene pools. These results and rich genomic resources broaden our understanding of recombination behavior in allopolyploids and may advance rapeseed genetic improvement.

BnaSD.C3 is a novel major quantitative trait locus affecting semi-dwarf architecture in Brassica napus L.

Plant height is a key plant architectural trait that affects the seed yield,harvest index and lodging resistance in Brassica napus L.,although the genetic mechanisms affecting plant height remain unclear.Here,a semi-dwarf mutant,df34,was obtained by ethyl methanesulphonate-induced mutagenesis.Genetic analysis showed that the semi-dwarf phenotype is controlled by one semi-dominant gene,which was located on chromosome C03 using a bulked segregant analysis coupled with whole-genome sequencing,and this gene was named BnaSD.C3.Then BnaSD.C3 was fine-mapped to a 297.35-kb segment of the“Darmor-bzh”genome,but there was no potential candidate gene for the semi-dwarf trait underlying this interval.Furthermore,the interval was aligned to the Zhongshuang 11 reference genome.Finally,combining structural variation analysis,transcriptome sequencing,phytohormone analyses and gene annotation information,BnaC03G0466900ZS and BnaC03G0478900ZS were determined to be the most likely candidate genes affecting the plant height of df34.This study provides a novel major locus for breeding and new insights into the genetic architecture of plant height in B.napus.