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Cytokinins are a class of phytohormones that promote cell division and differentiation and are thought to affect plant immunity to multiple pathogens. However, a comprehensive analysis of cytokinin dehydrogenase/oxidase (CKX) family genes in cabbage has not been reported. In this study, a total of 36 CKX genes were identified using a genome-wide search method. Phylogenetic analysis classified these genes into three groups. They were distributed unevenly across nine chromosomes in B. oleracea, and 15 of them did not contain any introns. The results of colinearity analysis showed that 36 CKX gene in Arabidopsis was present in several copies in the Brassica oleracea genome. An analysis of cis-acting elements indicated that all genes possessed at least one stress or hormone responsive cis-acting element. A heatmap of CKX gene expression showed the patterns of expression of these genes in various tissues and organs. Three genes (Bol028363, Bol031036 and Bol018140) were relatively highly expressed in all of the investigated tissues under normal conditions, showing the expression profile of housekeeping genes. Generally, the expression patterns of CKX genes in Jingfeng 1 and Xiangan 336 were quite different under the same treatment. Notably, three genes (Bol020547, Bol028392 and Bol045724) were significantly down-regulated and up-regulated in the susceptible and resistant material, respectively, after inoculation, which may indicate their crucial roles in resistance to clubroot disease. The results provide insights for better understanding the roles of CKX genes in the B. oleracea–P. brassicae interaction.

To better understand the genetic diversity and population structure of broccoli cultivars planted in China, a total of 161 representative broccoli cultivars in the past 25 years were collected and analysed based on single nucleotide polymorphism (SNP) markers. Ten pairs of primers with good polymorphism and high resolution were screened from 315 pairs of SNP primers by 3 broccoli accessions (inbred lines) with different phenotypes and maturity. The 10 pairs of SNP primers were selected, producing 78 alleles. The diversity analysis indicated that the polymorphism information content (PIC) of SNP primer ranged from 0.64 to 0.90. The observed number of alleles (Na) was 2.00, the effective number of alleles (Ne) was 1.11–2.00, the Nei's gene diversity (H) was 0.10–0.50, and Shannon information index (I) was 0.20–0.70 using PopGene32 software. The clustering results showed that the 161 broccoli cultivars could be divided into 4 major subgroups (A, B, C and D), foreign cultivars were all assigned to subgroup A, and domestic cultivars were assigned to 3 subgroups of B, C, and D. This study indicated that some domestic cultivars and foreign cultivars were similar in genetic background, but most domestic cultivars were still different from the Japanese cultivars. When K = 2, the population structure result presented that 161 broccoli cultivars could be divided into 1 simple group (2 groups) and 1 mixed group. When Q ≥ 0.6, 143(88.82%) broccoli cultivars belonged to the simple groups. In simple groups 68 (42.24%) broccoli cultivars of group 1 were derived from Japan, the United States, Switzerland, the Netherlands, China-Taiwan, and China-Mainland; 75 (46.58%) broccoli cultivars belonged to group 2; when Q

Cabbage (Brassica oleracea var. capitata) is an important vegetable crop widely grown throughout the world, providing plentiful nutrients and health-promoting substances. To facilitate further genetics and genomic studies and crop improvement, we present here a high-quality reference genome for cabbage. We report a de novo genome assembly of the cabbage double-haploid line D134. A combined strategy of single-molecule real-time (SMRT) sequencing, 10× Genomics and chromosome conformation capture (Hi-C) produced a high quality cabbage draft genome. The chromosome-level D134 assembly is 529.92 Mb in size, 135 Mb longer than the current 02-12 reference genome, with scaffold N50 length being raised as high as 38 times. We annotated 44,701 high-quality protein-coding genes, and provided full-length transcripts for 45.59% of the total predicted gene models. Moreover, we identified novel genomic features like underrated TEs, as well as gene families and gene family expansions and contractions during B. oleracea evolution. The D134 draft genome is a cabbage reference genome assembled by SMRT long-read sequencing combined with the 10× Genomics and Hi-C technologies for scaffolding. This high-quality cabbage reference genome provides a valuable tool for improvement of Brassica crops.

Key messageOgura CMS fertility-restored materials, with 18 chromosomes, normal seed setting, stable fertility and closer genetic background to the parent Chinese kale, were successfully developed inB. oleraceavia a triploid strategy for the first time.AbstractOgura cytoplasmic male sterility (CMS) is the most widely used sterile type in seed production for commercial hybrids ofBrassica oleraceavegetables. However, the natural Ogura CMS restorer line has not been found inB. oleraceacrops. In this study, the triploid strategy was used with the aim to create euploidB. oleraceaprogenies with theRfogene. The allotriploid AAC hybrid YL2 was used as a male parent to backcross with Ogura CMS Chinese kale. After successive backcrosses, the BC2Rfo-positive individual 16CMSF2-11 and its BC3progenies, with 18 chromosomes, were developed, which were morphologically identical to the parent Chinese kale. Compared with F1and BC1plants, it showed stable fertility performance, and regular meiosis behavior and could produce seeds normally under natural pollination. The genomic composition analysis ofRfo-positive progenies by using molecular markers showed that more than 87% of the C-genome components of BC3Rfo-progenies recovered to the parent Chinese kale, while most or all of theAn-genome segments were lost in 16CMSF2-11 and its progenies. The results suggested that the genetic background ofRfo-positive individuals was closer to that of the parent Chinese kale along with backcrossing. Hereof, the Ogura CMS fertility-restored materials of Chinese kale were successfully created via triploid strategy for the first time, providing a bridge for utilizing the Ogura CMSB. oleraceagermplasm in the future. Moreover, our study indicates that the triploid strategy is effective for transferring genes fromB. napusintoB. oleracea.

Ornamental kale is popular because of its colorful leaves and few studies have investigated the mechanism of color changes. In this study, an ornamental kale line (S2309) with three leaf colors was developed. Analysis of the anthocyanin, chlorophyll, and carotenoid contents and RNA-seq were performed on the three leaf color types. There was less chlorophyll in the white leaves and purple leaves than in the green leaves, and the anthocyanin content was greatest in the purple leaves. All the downregulated DEGs related to chlorophyll metabolism were detected only in the S2309_G vs. S2309_W comparison, which indicated that the decrease in chlorophyll content was caused mainly by the inhibition of chlorophyll biosynthesis during the leaf color change from green to white. Moreover, the expression of 19 DEGs involved in the anthocyanin biosynthesis pathway was upregulated. These results provide new insight into the mechanisms underlying the three-color formation.

Cabbage Fusarium wilt (CFW) disease, caused by the soil-borne fungus Fusarium oxysporum f. sp. conglutinans (Foc), threatens cabbage production worldwide. We aimed to explore the molecular mechanism of CFW resistance and the avirulence/virulence factors of Foc. The resistant ‘96–100’ and susceptible ‘01–20’ cabbage lines were examined histologically and in RNA-seq analyses. The key differentially expressed genes (DEGs) and pathways of both the host and fungus were determined via bioinformatics databases and tools. After inoculation, Foc began to colonize in the root of 01–20 at approximately 3 dpi and almost covered the root at 9 dpi, while the colonization was inhibited in 96–100. 96,142 and 3152 unigenes were generated for cabbage and Foc, respectively, by de novo assembly. For cabbage, there were 42,056 and 37,346 DEGs in 01–20 and 96–100 at all time points. Plant-pathogen interaction (map04626) was the major enrichment pathway among the DEGs. Many NBS-LRR genes and WRKY transcription factors were identified with different expression levels between 96 and 100 and 01–20. For Foc, 977 upregulated genes and 113 downregulated genes were identified, and the pathway of ribosome (map03010) was greatly enriched. There were 1 potential effectors, 2 elicitors and 6 virulence factors with increased or decreased transcript abundance among Foc DEGs, which deserved further functional validation. The RNA-seq data were further validated by qRT-PCR. Our results provide a distinct dual transcriptomic landscape to reveal the molecular mechanisms of cabbage resistance to Foc, and expand our understanding of the interaction between plant hosts and their fungal pathogens.

As a promising component for body sensor networks, the wearable sensors for hand gesture recognition have increasingly received great attention in recent years. By interpreting human intentions through hand gestures, the natural human–robot interaction can be realized in the smart home where the youth and the elderly can perform hand gestures to control the household robot or the robotic wheelchair. Here, a wearable wrist-worn camera sensor was shown to recognize hand trajectory gestures. The moving velocity of the user’s hand was deduced from the matched speeded up robust features keypoints of the moving background of the video sequence. Furthermore, the segmentation of continuous gestures was achieved by detecting the predefined gesture starting signal from the hand region of the image, which was segmented by the lazy snapping algorithm. In this paper, 10 types of gestures and 1350 gesture samples collected from 15 subjects at three different scenes were classified by the dynamic time warping algorithm and the results achieved an average recognition accuracy up to 97.6%. Moreover, the practicability of the proposed system was further demonstrated by controlling a cooperative robot to draw letters on paper.

Clubroot, caused by the soil-borne protist Plasmodiophora brassicae, is one of the most destructive disease for Brassica oleracea worldwide. However, the molecular mechanism of clubroot resistance still remains poorly elucidated. Therefore, we aim at identifying key genes responsive to P. brassicae infection and deducing possible molecular mechanism regulating clubroot resistance in cabbage. A clubroot-resistant line (XG) and a clubroot-susceptible line (JF) were employed to conduct histological observation and transcriptome analysis at 7 and 28 DAI (days after inoculation) following inoculation with P. brassicae. Differentially expressed genes (DEGs) obtained by comparing infected roots with mock-infected roots were assigned to Gene Ontology (GO) functions and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for enrichment analysis. TEM observation showed obvious histological differences of root cells between JF and XG after inoculation with P. brassicae. At 7 DAI, the number of DEGs identified in JF was much higher than that of XG, and most of them were enriched in metabolic pathways, metabolites biosynthesis and starch, sucrose metabolism. More DEGs were identified at 28 DAI compared to 7 DAI in XG, and most of these DEGs involved in biosynthesis of secondary metabolites, plant-pathogen interaction and plant hormone transduction. Genes related to cell wall biosynthesis, pattern recognition receptors (PRRs), disease resistance proteins, SA signal transduction, calcium influx, respiratory burst oxidase homolog (RBOH), MAPK cascades, transcription factors and chitinase were mainly up-regulated in XG at 28 DAI, while most of them were repressed in JF. Our research work suggest drastic and complex defense response to P. brassicae infection at 28 DAI (secondary infection stage) at transcriptional level. Results generated in the present study could provide comprehensive insights into the transcriptomic landscape for better understanding of molecular regulatory mechanism of clubroot resistance in cabbage.

Broccoli is a worldwide vegetable famous for good nutrition that is particularly rich in sulforaphane. The evolution of 95 broccoli cultivars that were widely collected and cultivated in China since 1980 was evaluated using 35 pairs of SSR markers. Thirty-five markers were selected from 960 pairs of SSR markers designed from Brassica oleracea, rapa and napus by two resources with different maturity periods. The results revealed that all 35 pairs of SSR markers were polymorphic, and 167 alleles were amplified with an average of 4.8 per marker. The mean content was 0.79 for polymorphism information, with a range from 0.48 to 0.99. The genetic diversity indexes ranged from 0.6909 to 0.8969, with an average of 0.7809. Genetic diversity analysis indicated the 95 genotypes could be separated into five primary sub-groups at a 0.72 distance. Sub-group A included more than 70% of genotypes with early and mid-early maturating cultivars, and the cultivars covered more than 87% of the genotypes of the 95 materials, including the primary cultivars widely planted that directed the domestication of broccoli in China in the past 37 years. Sub-groups B and C contained one inbred line with high generation and one DH line, respectively, suggesting both were innovative resources in cultivation. Sub-groups D and E were all inbred lines, and sub-group D had six members with similar characteristics: small florets, high-domed head, tall plants with nearly no lateral branches and good heat tolerance. Sub-group E had five members that presented similar wrinkle leaf morphology, and most matured at an intermediate rate, except IVF-B18. In this study, the evolution of broccoli cultivars in China was first summarized overall, together with their characteristics and distributions in China. Our study provides important information on genetic diversity and for cultivar replacement of broccoli in China, in addition to two new germplasms and polymorphism markers for research and molecular breeding.

Background Brassica oleracea exhibits extensive phenotypic diversity. As an important trait, petal color varies among different B. oleracea cultivars, enabling the study of the genetic basis of this trait. In a previous study, the gene responsible for petal color in B. oleracea was mapped to a 503-kb region on chromosome 3, but the candidate gene has not yet been identified. Results In the present study, we report that the candidate gene was further delineated to a 207-kb fragment. BoCCD4, a homolog of the Arabidopsis carotenoid cleavage dioxygenase 4 (CCD4) gene, was selected for evaluation as the candidate gene. Sequence analysis of the YL-1 inbred line revealed three insertions/deletions and 34 single-nucleotide polymorphisms in the coding region of BoCCD4. Functional complementation showed that BoCCD4 from the white-petal inbred line 11–192 can rescue the yellow-petal trait of YL-1. Expression analysis revealed that BoCCD4 is exclusively expressed in petal tissue of white-petal plants, and phylogenetic analysis indicated that CCD4 homologs may share evolutionarily conserved roles in carotenoid metabolism. These findings demonstrate that BoCCD4 is responsible for white/yellow petal color variation in B. oleracea. Conclusions This study demonstrated that function loss of BoCCD4, a homolog of Arabidopsis CCD4, is responsible for yellow petal color in B. oleracea. Electronic supplementary material The online version of this article (10.1186/s12864-019-5596-2) contains supplementary material, which is available to authorized users.

Glucoraphanin is a major secondary metabolite found in Brassicaceae vegetables, especially broccoli, and its degradation product sulforaphane plays an essential role in anticancer. The fine mapping of sulforaphane metabolism quantitative trait loci (QTLs) in broccoli florets is necessary for future marker-assisted selection strategies. In this study, we utilized a doubled haploid population consisting of 176 lines derived from two inbred lines (86,101 and 90,196) with significant differences in sulforaphane content, coupled with extensive genotypic and phenotypic data from two independent environments. A linkage map consisting of 438 simple sequence repeats markers was constructed, covering a length of 1168.26 cM. A total of 18 QTLs for sulforaphane metabolism in broccoli florets were detected, 10 were detected in 2017, and the other 8 were detected in 2018. The LOD values of all QTLs ranged from 3.06 to 14.47, explaining 1.74–7.03% of the biochemical variation between two years. Finally, 6 QTLs (qSF-C3-1, qSF-C3-2, qSF-C3-3, qSF-C3-5, qSF-C3-6 and qSF-C7) were stably detected in more than one environment, each accounting for 4.54–7.03% of the phenotypic variation explained (PVE) and a total of 30.88–34.86% of PVE. Our study provides new insights into sulforaphane metabolism in broccoli florets and marker-assisted selection breeding in Brassica oleracea crops.

Comparative morphological, transcriptomic and phytohormone analyses reveal a defence network leading to PCD involved in cabbage hybrid lethality. Hybrid lethality (HL) plays an essential role in the stability of a population by blocking gene exchange between species, but the molecular mechanism remains largely undetermined. In this study, we performed phenotype, transcriptome and plant hormone analyses of HL in cabbage. Phenotype analysis confirmed that HL is characterised by a typical programmed cell death (PCD) process. A time-resolved RNA-Seq identified 2724 differentially expressed genes (DEGs), and functional annotations analyses revealed that HL was closely associated with the defence response. A defence regulation network was constructed based on the plant–pathogen interaction pathway and MAPK signalling pathway, which comprised DEGs related to Ca2+ and hydrogen peroxide (H2O2) leading to PCD. Moreover, important DEGs involved in hormone signal transduction pathways including salicylic acid (SA) and jasmonic acid (JA) were identified, which were further confirmed by endogenous and exogenous SA and JA measurements. Our results identified key genes and pathways in the regulating network of HL in cabbage, and might open the gate for revealing the molecular mechanism of HL in plants.

With the development of smart sensing and the aging trend of the society, telerobot is playing an increasingly important role in the field of homecare service. In this article, we present the design, implementation, and evaluation of a wearable sensor glove. The sensor glove is based on inertial measurement units (IMUs) with 9 axes. We put 6 nodes on the glove and calculate the quaternions of all the orientations of the knuckles with fusion algorithm and interpolation algorithm. The main goal of this research is to develop a human-robot interface in order to help to control the telerobot remotely. This paper mainly deals with three issues: 1) designing a simple and extensible motion capture system architecture, 2) choosing a simple but effective fusion algorithm for motion capture, 3) performance evaluation of the sensor glove based on IMUs. The experimental results suggest that the sensor glove we designed can meet the requirements of speed and accuracy. Furthermore, the architecture we designed can not only be used on the sensor glove, it can also be extended to up to 128 nodes to capture the motion of the hole body.

With the development of intelligent sensing and human-robot interaction technology, homecare robots play an increasingly important role in the field of homecare services. At the same time, the interaction between the operator and the homecare robot is particularly valued. This paper proposed a homecare robot interaction system based on a wearable inertial motion capture device. In this system, the wearable motion capture device is used to capture the operator’s motion signals. After processing the motion signals and recognizing the corresponding motion poses, the system controls the homecare robot to imitate the intention of the operator. In this paper, we focused on controlling the movement of the homecare robot through the operator’s lower limb motion data and designed a novel gait recognition algorithm. The proposed system was evaluated experimentally, proving that the system has strong performance and practicality.

Cabbage is a globally cultivated vegetable with obvious heterosis. The main method used for cabbage breeding is the creation of hybrid combinations with inbred lines, and how to combine the parents plays a crucial role in cabbage breeding. Therefore, it is urgent to classify heterotic groups by molecular markers. In this study, single nucleotide polymorphism (SNP) markers were developed on the basis of whole-genome resequencing data of 50 inbred lines. A total of 2.54 × 106 SNP loci were obtained by aligning resequencing data to the reference genome of cabbage. Finally, five hundred SNP markers among 50 re-sequenced genotypes were further selected on the basis of a high polymorphism information content, a high minor allele frequency, a wide average distribution and low heterozygosity. Then, 442 SNP markers were successfully converted into kompetitive allele-specific PCR (KASP) markers, accounting for 88.4% of all 500 SNP markers. The cabbage inbred lines included three ecotypes: spring cabbage, autumn cabbage and winter cabbage. Based on the KASP genotyping data, the genetic similarity among inbred lines was analyzed, and the heterotic groups within each ecotype were classified. Seven heterotic groups were identified for spring cabbage (77); six, for autumn cabbage (70); and five, for winter cabbage (97). In addition, we found parents of 48 developed elite combinations were all from different heterotic groups or subgroups, which verified that the group classification was accurate and useful. Therefore, we suggest that the parents of combinations should be selected from different heterotic groups or subgroups, which will guide parental selection in cabbage breeding and improve breeding efficiency.

Background: Virus-induced gene silencing (VIGS), a posttranscriptional gene silencing method, represents an effective technology for the analysis gene functions in plants. However, no VIGS vectors are available for Brassica oleracea till now. The gene silencing vectors TRV, pTYs and CaLCuV were chose to improve the VIGS system in cabbage, using phytoene desaturase (PDS) gene as an efficient visual indicator for VIGS.Results: We successfully silenced the expression of PDS and observed the photobleaching phenomenon in cabbage by pTYs and CaLCuV, with the latter displaying higher efficiency and lower cost. Then, the factors potentially affecting the silencing efficiency of VIGS by CaLCuV in cabbage, including targeting fragment strategy, inoculation method and incubation temperature, were compared. The optimized CaLCuV-based VIGS system is as follows: approximately 500 bp insert sequence, Agrobacterium OD600=1.0, vacuum osmosis method at the bud stage, and the incubation temperature of 22 °C, through which we achieved a stable silencing efficiency of 65%. To further test the effectiveness of the system, we selected two other genes in cabbage including Mg-chelataseH subunit (ChlH) and lobed-leaf 1 (LL1) to knock down their expression, and we observed the expected yellow or lobed leaves. In addition, we successfully applied the CaLCuV-based VIGS system in two other representative Brassica crops including B. rapa and B. nigra and thus expanded its application scope.Conclusion: These results demonstrate that CaLCuV-based VIGS effectively work in cabbage and can be used for analyzing gene function. Our VIGS system described here will contribute to efficient functional genomics research in Brassica crops.

Clubroot disease, a major plant root disease caused byPlasmodiophora brassicae, has become one of the most destructive diseases among cultivated cruciferous vegetables. However, clubroot-resistantBrassica oleraceamaterials are rare. A few clubroot-resistant cabbage varieties are available on the market, but all are Ogura cytoplasmic male sterile (CMS) types. Therefore, in this study, to reutilize the clubroot-resistant Ogura CMS germplasm of cabbage, a new fertility-restored Ogura CMS material, 16Q2-11, was used as a bridge to transfer the clubroot resistance (CR) gene from the Ogura CMS cytoplasm to the normal cytoplasm by a two-step method (a fertility restoration and cytoplasm replacement method). In the first cross for fertility restoration of Ogura CMS clubroot-resistant cabbage (FRCRC), 16Q2-11 was used as a restorer to cross with Ogura CMS materials containing the CR geneCRb2. ElevenRfo-positive progenies were generated, of which four containedCRb2: F8-514, F8-620, F8-732 and F8-839. After inoculation with race 4 ofP. brassicae, these fourCRb2-positive individuals showed resistance. Furthermore, F8-514 and F8-839 were then used as male parents in the second cross of FRCRC to cross with cabbage inbred lines, resulting in the successful introgression of theCRb2gene into the inbred lines. All offspring produced from this step of cross, which had a normal cytoplasm, showed a high resistance to race 4 ofP. brassicaeand could be utilized for the breeding of clubroot-resistant cabbage varieties in the future. This is the first time that the Ogura CMS restorer has been used to restore the fertility of Ogura CMS clubroot-resistant cabbages, which could improve germplasm diversity in cabbage and provide a reference method for using CMS germplasm inBrassicacrops.

Microspore embryogenesis (ME), a widely used haploid breeding method that can considerably shorten the breeding cycle, provides an efficient mean of cultivating many important Brassica crops, such as cabbage, Chinese cabbage, and oilseed rape. For cabbage, in many cases, short-term heat shock treatment can strongly increase the embryogenesis rate, however, the underlying mechanism of this effect has not been elucidated. In this study, we compared the proteomics of isolated microspores with samples pretreated at 32 °C for 24 h and 25 °C for 24 h using two cabbage accessions (Zhonggan 628 and 87–534) showing highly different embryogenic rates. The embryo yield was 19.7 embryos/bud in Zhonggan 628 after 32 °C treatment, while no embryoid was observed in Zhonggan 628 after 25 °C treatment as well as in 87–534 at both temperatures. We identified a total of 363 and 282 differentially expressed proteins (DEPs) for Zhonggan 628 and 87–534 via a label-free proteomics technology. There were 97 DEPs specifically identified only in Zhonggan 628 but not in 87–534 after 32 °C heat-shock treatment that may be related to heat shock-induced embryogenesis in vitro culture. These DEPs were primarily enriched in carbon metabolic process, protein synthesis and degradation process, and signal transduction. Based on protein-protein interaction and pathway enrichment analyses, we proposed that SGT1 homolog A and B(SGT1), heat shock 70 kDa protein 5 (HSP70), cell division control protein 48 homolog A (CDC48) and fatty acyl-CoA reductase (FAR) might play important roles in microspore embryogenesis. This proteomic study may contribute to our molecular understanding of cabbage microspore embryogenesis and help to build a high-efficiency haploid breeding system.

Brassica species include many economically important crops that provide nutrition and health-promoting substances to humans worldwide. However, as with all crops, their production is constantly threatened by emerging viral, bacterial, and fungal diseases, whose incidence has increased in recent years. Traditional methods of control are often costly, present limited effectiveness, and cause environmental damage; instead, the ideal approach is to mine and utilize the resistance genes of the Brassica crop hosts themselves. Fortunately, the development of genomics, molecular genetics, and biological techniques enables us to rapidly discover and apply resistance (R) genes. Herein, the R genes identified in Brassica crops are summarized, including their mapping and cloning, possible molecular mechanisms, and application in resistance breeding. Future perspectives concerning how to accurately discover additional R gene resources and efficiently utilize these genes in the genomic era are also discussed.

TIFY, a plant-specific gene family with the conserved motif TIF[F/Y]XG, plays important roles in various plant biological processes. Here, a total of 36 TIFY genes were identified in the Brassica oleracea genome and classified into JAZ (22 genes), TIFY (7 genes), ZML (5 genes), and PPD (2 genes) subfamilies based on their conserved motifs, which were distributed unevenly across nine chromosomes with different lengths (339&ndash, 1077 bp) and exon numbers (1&ndash, 8). Following phylogenetic analysis with A. thaliana and B. rapa TIFY proteins, ten clades were obtained. The expression of these TIFY genes was organ-specific, with thirteen JAZ genes and two PPD genes showing the highest expression in roots and leaves, respectively. More importantly, the JAZs showed divergent responses to various pathogen infections and different phytohormone treatments. Compared with the susceptible line, most JAZs were activated after Plasmodiophora brassicae infection, while there were both induced and inhibited JAZs after Fusarium oxysporum or Xanthomonas campestris infection in the resistance line, indicating their probably distinct roles in disease resistance or susceptibility. Further, the JAZs were all upregulated after MeJA treatment, but were mostly downregulated after SA/ET treatment. In summary, these results contribute to our understanding of the TIFY gene family, revealing that JAZs may play crucial and divergent roles in phytohormone crosstalk and plant defense.

The ms3 gene responsible for a male-sterile phenotype in cabbage was mapped to a 187.4-kb genomic fragment. The gene BoTPD1, a homolog of Arabidopsis TPD1, was identified as a strong candidate gene. Cabbage 51S is a spontaneous male-sterile mutant. Phenotypic investigation revealed defects in anther cell differentiation, with failure to form the tapetum layer and complete abortion of microsporocytes before the tetrad stage. Genetic analysis indicated that this male sterility was controlled by a single recessive gene, ms3. Using an F2 population, we mapped ms3 to a 187.4-kb interval. BoTPD1 was identified as a candidate from this interval. Sequence analysis revealed an intronic 182-bp insertion in 51S that interrupted the conserved motif at the 5′ splicing site of the third intron, possibly resulting in a truncated transcript. Analyses of BoTPD1 homologous proteins revealed evolutionarily conserved roles in anther cell fate determination during reproductive development. RT-PCR showed that BoTPD1 was expressed in various tissues, excluding the root, and high expression levels were detected in anthers and buds. A BoTPD1-specific marker based on the 182-bp insertion cosegregated with male sterility and can be used for marker-assisted selection.

Cabbage is one of the most important cruciferous vegetables worldwide including China. Clubroot, caused by Plasmodiophora brassicae, occurs on most cruciferous crops and causes great yield losses. Utilization of resistant cultivar is the principal way to combat clubroot. To provide resistant sources for breeding, 102 cabbage genotypes were evaluated for seedling resistance to P. brassicae race 4, which is the predominant race in China. Results of repetitive identifications showed that Xiangan336 was highly resistant to clubroot, and four resistant genotypes including Verheul, Bindsachsener, Zhouyebai and 2358 were identified as resistant. Marker analysis suggested that Xiangan336 carried the clubroot resistance gene CRb. To clarify the infection characteristic of P. brassicae and deduce the resistance mechanism of cabbage, the infection process in Xiangan336 and Jingfeng No.1 (highly susceptible) were observed and compared. The significantly lower level of primary infection in Xiangan336 than that in Jingfeng No.1 at 4 dai (days after inoculation) indicated the early defense against P. brassicae in resistant genotype. However, the accumulated secondary plasmodia in Xiangan336 were more abundant than in Jingfeng No.1 from 7 to 21 dai and then declined significantly after 28 dai, suggesting that the clubroot-specific resistance mechanism may restrict the proliferation of P. brassicae after 28 dai. Histological observation verified that the development of P. brassicae from secondary plasmodia to resting spores was restricted within cortex cells in Xiangan336. The identified resistant genotypes will be of great value for resistance breeding and the analysis of infection process will further improve our understanding of resistance mechanism.

Winter cabbage is an important crop cultivated through winter in the region near the Yangtze River, enabling the supply of fresh cabbage there at that time of year. However, a problem has emerged regarding the newly developed parents of winter cabbage, which is completely different from spring and autumn cabbage, namely, how to combine these parents to breed an elite hybrid. To classify the heterotic groups and improve the efficiency of parent selection in winter cabbage breeding, 20 polymorphic SSR markers were selected to screen 63 winter cabbage inbred lines. Seventeen pairs among the 20 SSR markers amplified polymorphic bands. These primers amplified two to six bands, with an average of 2.8 bands per primer, and a total of 47 polymorphic bands were generated in the 63 inbred lines. These lines included flat-headed morphotype and round-headed morphotype, thus they were separately classified into heterotic groups based on the SSR markers. The flat-headed morphotype contained 21 inbred lines and was classified into three heterotic groups, named Hanchun 4, Jiali, and Dongsheng, in accordance with the representative germplasm contained in each group. The round-headed morphotype contained 42 inbred lines and was classified into five heterotic groups, named Parte, Bejo1039, YK-143, SCA002, and Golden B90. Meanwhile, parent analysis of 20 developed elite combinations showed that their parents were all distributed in different heterotic groups, indicating that the group classification was reasonable, which can provide a basis for further parent selection in winter cabbage breeding. Furthermore, polymorphic SSR primers were successfully used to identify the hybrid purity of three elite varieties. Keywords: winter cabbage, head morphotype, SSR marker, heterotic group, hybrid purity identification

Plant male reproductive development is a very complex biological process that involves multiple metabolic pathways. To reveal novel insights into male reproductive development, we conducted an integrated profiling of gene activity in the developing buds of a cabbage recessive genetic male sterile mutant. Using RNA-Seq and label-free quantitative proteomics, 2881 transcripts and 1245 protein species were identified with significant differential abundance between the male sterile line 83121A and its isogenic maintainer line 83121B. Analyses of function annotations and correlations between transcriptome and proteome and protein interaction networks were also conducted, which suggested that the male sterility involves a complex regulatory pattern. Moreover, several key biological processes, such as fatty acid metabolism, tapetosome biosynthesis, amino acid metabolism and protein synthesis and degradation were identified as being of relevance to male reproductive development. A large number of protein species involved in sporopollenin synthesis, amino acid synthesis, ribosome assembly, protein processing in endoplasmic reticulum and lipid transfer were observed to be significantly down-accumulated in 83121A buds, indicating their potential roles in the regulation of cabbage microspore abortion. In summary, the conjoint analysis of the transcriptome and proteome provided a global picture regarding the molecular dynamics in male sterile buds of 83121A. Biological significance Male sterile mutants are excellent materials for the study of plant male reproductive development. This study revealed the molecular dynamics of recessive male sterility in cabbage at the transcriptome and proteome levels, which deepens our understanding of the metabolic pathways involved in male development. Moreover, the male sterility-related genes identified in this study could provide a reference for the artificial regulation of cabbage fertility by using genetic engineering technology, which may result in potential applications in agriculture such as production of hybrid seeds using male sterility.

s Xanthomonas campestris pv. campestris (Xcc) is the causal agent of cabbage (Brassica oleracea var. capitata) black rot (BR) that leads to severe yield losses worldwide. Cultivation and application of resistant cultivars is the most desirable way to control BR. However, due to the lack of BR-resistant germplasm resources and an unclear understanding of the resistance inheritance as well as the controlling gene, the breeding process has been seriously hindered. To identify new BR resistance sources to Xcc race 1, 162 cabbage accessions collected worldwide were evaluated using the spray inoculation method. In total, 64.2% of them were susceptible, and only four germplasms were highly resistant, including two inbred lines (‘05-574-323’ and ‘MD219’) and two hybrids (‘Qinglian’ and ‘Dadilv 2’). Further, to define the genetic characteristics of resistance, a mixed major gene plus polygene inheritance model was used to analyze BR resistance in six populations (P1, P2, F1, B1, B2, and F2) derived from the resistant parent ‘05-574-323’ and the susceptible parent ‘02-359’. The results showed that BR resistance was controlled by a pair of additive major genes and additive-dominant multiple genes (D-2 model), and the main gene heritabilities of B1, B2, and F2 were 49.29%, 43.53%, and 50.35%, respectively. The resistant accessions obtained in this study provide new resources for cabbage BR-resistance breeding, and the inheritance analysis opens the gate for further mapping and application of the resistance gene.

Plant cytochrome P450 monooxygenases (CYPs) make up a large superfamily of heme-thiolate enzymes involving in many primary and secondary metabolism reactions. In this study, a total of 279 Brassica oleracea CYP (BoCYP) genes were identified in the cabbage genome. These BoCYPs were classified into eight distinct clans with 44 families. Expression analyses of the BoCYP genes of different cabbage tissues suggested that some BoCYPs may play significant roles in reproduction. Recently, BoCYP704B1 has been identified as a candidate gene associated with male sterility in the cabbage line 83121A. Here, the functional mechanism of BoCYP704B1 was explored. Subcellular localization showed that BoCYP704B1 is located in the endoplasmic reticulum. RNA in situ hybridization indicated that BoCYP704B1 is predominantly expressed in the tapetum of cabbage anther, and the expression was maximal at the tetrad and early monocyte stage and weakened to the termination. Furthermore, functional complementation test results showed that BoCYP704B1 from wild type could rescue the male sterility of 83121A mutant. The results of this study increase our understanding of the functional mechanism of cabbage CYP genes and will facilitate the application of the BoCYP704B1 gene in cabbage molecular breeding.

Indole-3-carbinol is a potential anti-cancer agent, and it has been found rich in Brassica vegetables. However, there was few good extraction method of indole-3-carbinol in cabbage and broccoli. In this work, the wavelength and the ration of mobile phase in determination method, as well as different temperature and pH values in extraction method were all investigated some cultivars of cabbage and broccoli were collected and validated the determination method. A sensitive and rapid high-performance liquid chromatography method has been established and used for the determination of indole-3-carbinol in cabbage (Brassica oleracea L. var. capitata) and broccoli (Brassica oleracea L. var. italica). The method was proved to be sensitive, selective, rapid and reproducible, with a good recovery of 99.25%. There was a fast retention time (4.88 min) and good linearity (R2=0.9991) in the system. Meanwhile, significant differences of indole-3-carbinol contents were detected among all the materials (P

Brassica oleracea comprises several important subspecies, including cabbage, broccoli, cauliflower, Chinese kale, and kohlrabi. The petal color of Chinese kale is mostly white and sometimes yellow. To explore the genetic basis of petal color variation in Chinese kale, F2 and BC1 (backcross) populations were constructed from the cross of two inbred lines, 2114 (yellow petal) and 2116 (white petal). Genetic analysis of the F2 and BC1 populations demonstrated that yellow petal color was controlled by a single recessive nuclear gene, termed cpc-2. Insertion-deletion (InDel) markers, designed based on the parental resequencing data, were used to map cpc-2. The fine mapping results indicated that the cpc-2 gene was located in a 569-kb interval on chromosome C03 flanked by InDel markers ZB636 and ZB692, with genetic distances of 0.3 cM and 0.6 cM, respectively. By analyzing the nucleotide variations and annotations of the genes in this interval, a CCD4 family gene was predicted to be a candidate for cpc-2 and renamed BoCCD4.2. In addition, insertion of the CACTA-like transposable element (TE3) interrupted the function of the BoCCD4 gene, which may have resulted in the loss of function of BoCCD4 and the petal color transition from white to yellow. The TE3 insertion in the BoCCD4 gene was also present in 63 cabbage inbred lines among 159 accessions, which revealed that the TE3-type null allele of BoCCD4 formed before the divergence of the two subspecies cabbage and Chinese kale and that Chinese kale evolved much earlier than cabbage. This study lays the foundation for cloning BoCCD4.2 and revealing the molecular mechanism underlying petal color formation in Chinese kale.

Plant dwarf mutants generally exhibit delayed growth, delayed development, short internodes, and abnormal leaves and flowers and are ideal materials to explore the molecular mechanism of plant growth and development. In the current study, we first discovered a spontaneous cabbage (Brassica oleracea) dwarf mutant 99–198dw, which exhibits a dwarf stature, wrinkled leaves, non-heading, and substantially reduced self-fertility compared with the wild-type 99–198; however, the underlying molecular mechanism of its dwarfism is unknown. Here, we performed comparative phenotype, transcriptome and phytohormone analyses between 99–198 and 99–198dw. Cytological analysis showed that an increase in cell size, a reduction in cell layers, chloroplast degradation and a reduction in mitochondria were observed in 99–198dw. RNA-Seq showed that a total of 3801 differentially expressed genes (DEGs) were identified, including 2203 upregulated and 1598 downregulated genes in the dwarf mutant. Key genes in stress-resistant pathways were mostly upregulated, including salicylic acid (SA), jasmonic acid (JA), abscisic acid (ABA), ethylene (ET), etc., while the DEGs reported to be related to plant height, such as those involved in the gibberellin (GA), brassinolide (BR), indole-3-acetic acid (IAA), and strigolactone (SL) pathways were mostly downregulated. In addition, the DEGs in the cell division pathway were all downregulated, which is consistent with the cytokinesis defects detected by cytological analysis. The changes in the GA4, JA, ET, SA and ABA contents measured by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) absolute quantification were consistent with the transcriptome analysis. Further hormone treatment tests showed that the exogenous application of GA, BR, 6BA, paclobutrazol (PC), etc. did not rescue the phenotype, implying that the change in phytohormones is due to but not the cause of the dwarf trait. It was speculated that mutation of certain DEG related to cell division or participating in signalling pathway of phytohormones like GA, BR, IAA, and SL were the cause of dwarf. These results are informative for the elucidation of the underlying regulatory network in 99–198dw and enrich our understanding of plant dwarf traits at the molecular level.

Seed number per silique is a major factor that affects cabbage seed yield. To identify quantitative trait loci (QTL) related to seed number per silique and develop linked markers for cabbage molecular marker-assisted breeding, a double haploid (DH) population with 100 individuals, derived from two founder parents (01-20 and 96-100) with notable differences in seed number per silique, was subjected to whole-genome resequencing. Genotyping by sequencing (GBS) technology was applied to construct a high-density SNP-based genetic linkage group with 1465 bin markers, covering 1285.77 cM of genome length, with an average genetic distance of 0.88 cM between adjacent bin markers. Finally, one significant QTL, qSNS6.1, on chromosome 6 was repeatedly detected in two experimental years, with a mean contribute rate of 15.2% and LOD value of 3.1. The major QTL qSNS6.1 will facilitate further understanding of the genetic basis of seed number per silique, and the development of genetic markers linked with seed number per silique would save time and reduce labor intensity by allowing selection of this trait at the seeding stage of cabbage.

Broccoli is an important Brassica vegetable that shows obvious heterosis. The main method for hybrid broccoli production is to use cytoplasmic male sterility (CMS) and pollination by bees. Therefore, the evaluation and selection of high quality sources of CMS is important for broccoli breeding. We aimed to evaluate the effects of different CMS sources on the morphology and size of floral organs, the attractiveness to pollinators and yield of hybrid seeds. Using broccoli CMS lines generated from different CMS sources with the same maintainer lines, we studied morphophysiological characteristics of flowers, such as flower shape and size, nectar production and sugar content, as well as the number of bee visits and seed yield. The degree of bud abortion, floral organs shape, degree of flower opening, nectar production, bee visits, and hybrid yield differed in CMS lines with same recurrent parent. When the CMS source was same and the recurrent parents were different, the degrees of bud abortion were different among the CMS lines, while the flowering characteristics were similar. Generally, larger floral organs and higher volumes of nectar were associated with higher frequency of bee visits and higher seed yield. Based on the morphological characteristics and size of floral organs, nectar secretion, bee-attracting ability and hybrid yield, we selected four CMS sources suitable for future use in broccoli breeding. Our results will provide an important reference for breeding high-quality CMS lines in broccoli and provide valuable CMS sources for breeding other cruciferous crops.

Cabbage 79-399-3 is a spontaneous male-sterile mutant controlled by the dominant genic gene (DGMS) Ms-cd1. Dozens of DGMS lines in cabbage, broccoli, kohlrabi, and Chinese kale have been created using 79-399-3 as a donor. To realize fast and accurate marker-assisted selection (MAS) and build a high-efficiency breeding system based on DMGS, a high-throughput, user-friendly marker is needed. In this study, we resequenced the DGMS line DGMS01-20 (backcross lines with over 20 generations) and its maintainer line 01-20 and developed four markers linked to Ms-cd1 using a segregating population of DGMS01-20. Kompetitive allele specific PCR (KASP) markers K13 and K23 were the flanking markers with genetic distances of 0.76 cM and 1.09 cM, respectively. K6 cosegregated with Ms-cd1 in all 919 individuals of the population. K13 and K6 were tested for their accuracy and applicability using 18 different DGMS lines. K13 was not applicable in five broccoli, kohlrabi, and Chinese kale DGMS lines, resulting in 72.2% accuracy, whereas K6 showed 100% accuracy in these DGMS lines and in an additional assessment using 35 inbred lines. Moreover, K6 can be used to genotype the self-pollination progenies of heterozygous plants (heterozygous means one Ms-cd1 allele and one wild-type allele; such plants produce pollen grains in very rare cases). The results showed that K6 is a reliable marker for accurately and rapidly identifying Ms-cd1 loci in Brassica oleracea; thus, it is beneficial for the DGMS-based breeding program in B. oleracea.

Background Heat shock proteins have important functions in regulating plant growth and response to abiotic stress. HSP70 family genes have been described in several plant species, but a comprehensive analysis of the HSP70 family genes in cabbage has not been reported to date, especially their roles in floral development. Results In this study, we identified 52 BoHSP70 genes in cabbage. The gene structures, motifs, and chromosome locations of the BoHSP70 genes were analyzed. The genes were divided into seven classes using a phylogenetic analysis. An expression analysis showed that the BoHSP70 genes were highly expressed in actively growing tissues, including buds and calluses. In addition, six BoHSP70 genes were highly expressed in the binuclear-pollen-stage buds of a male fertile line compared with its near isogenic sterile line. These results were further verified using qRT-PCR. Subcellular localization analysis of the bud-specific gene BoHSP70–5 showed that it was localized in the cytoplasm. Conclusions Our results help to elucidate the involvement of the BoHSP70 family genes in cabbage floral development and establish the groundwork for future research on the functions of these genes. Electronic supplementary material The online version of this article (10.1186/s12864-019-5757-3) contains supplementary material, which is available to authorized users.

Cabbage hybrids, which clearly present heterosis vigor, are widely used in agricultural production. We compared two S5 haplotype (Class II) cabbage inbred-lines 87–534 and 94–182: the former is highly SC while the latter is highly SI; sequence analysis of SI-related genes including SCR, SRK, ARC1, THL1, and MLPK indicates the some SNPs in ARC1 and SRK of 87–534; semi-quantitative analysis indicated that the SI-related genes were transcribed normally from DNA to mRNA. To unravel the genetic basis of SC, we performed whole-genome mapping of the quantitative trait loci (QTLs) governing self-compatibility using an F2 population derived from 87–534 × 96–100. Eight QTLs were detected, and high contribution rates (CRs) were observed for three QTLs: qSC7.2 (54.8%), qSC9.1 (14.1%) and qSC5.1 (11.2%). 06–88 (CB201 × 96–100) yielded an excellent hybrid. However, F1 seeds cannot be produced at the anthesis stage because the parents share the same S-haplotype (S57, class I). To overcome crossing incompatibility, we performed rapid introgression of the self-compatibility trait from 87–534 to 96–100 using two self-compatibility-QTL-specific markers, BoID0709 and BoID0992, as well as 36 genome-wide markers that were evenly distributed along nine chromosomes for background analysis in recurrent back-crossing (BC). The transfer process showed that the proportion of recurrent parent genome (PRPG) in BC4F1 was greater than 94%, and the ratio of individual SC plants in BC4F1 reached 100%. The newly created line, which was designated SC96–100 and exhibited both agronomic traits that were similar to those of 96–100 and a compatibility index (CI) greater than 5.0, was successfully used in the production of the commercial hybrid 06–88. The study herein provides new insight into the genetic basis of self-compatibility in cabbage and facilitates cabbage breeding using SC lines in the male-sterile (MS) system.

Cabbage (Brassica oleracea) is an important vegetable crop that is cultivated worldwide. Previously, we reported the identification of two dominant complementary hybrid lethality (HL) genes in cabbage that could result in the death of hybrids. To avoid such losses in the breeding process, we attempted to develop molecular markers to identify HL lines. Among 54 previous mapping markers closely linked to BoHL1 or BoHL2, only six markers for BoHL2 were available in eight cabbage lines (two BoHL1 lines, three BoHL2 lines, three lines without BoHL), however, they were neither universal nor user-friendly in more inbred lines. To develop more accurate markers, these cabbage lines were resequenced at an ~20× depth to obtain more nucleotide variations in the mapping regions. Then, an InDel in BoHL1 and a single-nucleotide polymorphism (SNP) in BoHL2 were identified, and the corresponding InDel marker MBoHL1 and the competitive allele-specific PCR (KASP) marker KBoHL2 were developed and showed 100% accuracy in eight inbred lines. Moreover, we identified 138 cabbage lines using the two markers, among which one inbred line carried BoHL1 and 11 inbred lines carried BoHL2. All of the lethal line genotypes obtained with the two markers matched the phenotype. Two markers were highly reliable for the rapid identification of HL genes in cabbage.

The planting density of broccoli can directly affect the yield and overall health of plants. Nonetheless, studies on the genetic base of planting density in broccoli are rather limited. In this study, the important planting density-dependent factors of broccoli, plant height (PH), maximum outer petiole length (PL) and leaf width (LW), were investigated during 2017 and 2018. In this study, mapping of QTL for PH, PL and LW based on a DH population in broccoli, and as well as the interaction between QTLs and the environment. The DH population was constructed with 176 genotypes obtained from F1 hybrid produced by crossing two different inbred lines 86101 (P1) and 90196 (P2). In our study, a linkage group including a total of 438 SSR markers were constructed covering a length of 1168.26 cM using QTL IciMapping 4.0 software. Finally, there were mainly four QTLs (phc1, phc2, phc4−2, phc4−3), one QTL (plc6−2), and two QTLs (lwc1, lwc3−1) corresponding for PH, PL and LW recurred during the two years. In three environments, inclusive composite interval mapping (ICIM) analysis showed that there was a major QTL for PH at 7.20 cM on chromosome 1 with a high explanatory contribution rate of 20.05 %. The QTL at the 11.10 cM position of chromosome 6 was located for the PL with a high explanatory contribution rate of 20.02 %. The QTL at the 147.00 cM position of chromosome 3 was located on LW with a high explanatory contribution rate of 19.97 %. Interestingly, we found an overlap region (pplc4) in the chromosome 4 containing three QLTs for traits PH, PL, and LW (phc4−2, plc4−3, and lwc4−2). According to this study, the possible positions of candidate genes were screened to provide a basis for further locating and cloning genes for plant height, maximum outer petiole and leaf width, which would be beneficial to breeding of broccoli and the Brassica crops, especially in high planting density.

We aimed to characterize and quantify glucosinolate compounds and contents in broccoli, and a total of 80 genotypes and eight developmental organs were analyzed with UHPLC-Triple-TOF-MS. The method was validated in terms of performance, and the coefficients of determination (R2) were 0.97 and 0.99 for glucoraphanin and gluconapin, respectively. In 80 genotypes, twelve glucosinolates were found in broccoli florets ranging from 0.467 to 57.156 µmol/g DW, with the highest glucosinolate content being approximately 122-fold higher than the lowest value. The principal component of glucobrassicin, neoglucobrassicin and glucoraphanin explained 60.53% of the total variance. There were positive correlations among hydroxyglucobrassicin, methoxyglucobrassicin, glucobrassicin, glucoerucin, gluconasturtiin, glucoraphanin, and glucotropaeolin (P

Brassica oleracea is an important vegetable species which belongs to the genus Brassica and the mustard family Brassicaceae Burnett. Strong heterosis in B. oleracea is displayed in yield, quality, disease resistance, and stress tolerance. Heterosis breeding is the main way to improve B. oleracea varieties. Male sterile mutants play an important role in the utilization of heterosis and the study of development and regulation in plant reproduction. In this paper, advances in the research and application of male sterility in B. oleracea were reviewed, including aspects of the genetics, cytological characteristics, discovery of genes related to male sterility, and application of male sterility in B. oleracea. Moreover, the main existing problems and prospect of male sterility application in B. oleracea were addressed and a new hybrids’ production strategy with recessive genic male sterility is introduced.

Traits related to head shape, including Hvd (head vertical diameter), Htd (head transverse diameter), and Hsi (head shape index, the ratio of Hvd/Htd), are very important agronomic traits associated with both yield and quality in cabbage (Brassica oleracea var. capitata L.). However, reports of inheritance analysis and quantitative trait locus (QTL) mapping of these traits remain rare. In this study, a double haploid (DH) population with 130 lines constructed from a cross between 24-5 (inbred line, oblate head) × 01-88 (inbred line, round head) was used to analyze inheritance and to detect QTLs related to Htd and Hsi using major gene plus polygene mixed inheritance analysis and inclusive composite interval mapping (ICIM). The results indicated that Htd was controlled by two independent major genes and polygenes with recessive-epistatic effects. Hsi was controlled by two linkage major genes and polygenes with cumulative effects. A genetic linkage map with 48 insertions or deletions (InDel) and 149 simple sequence repeat (SSR) markers was constructed based on the DH population, with a total length of 866.2 cM and an average interval length of 4.40 cM. Fourteen QTLs for Htd and Hsi were identified on six chromosomes based on two years of phenotypic data with ICIM. Ten of the QTLs explained greater than 10.0% of the phenotypic variance, and five QTLs could be repeatedly detected in two years. For Htd, two major QTLs, Htd 3.1 and Htd 8.1, explained 19.16–24.56% and 11.25–21.55% of the phenotypic variation in the two years, respectively. For Hsi, two major QTLs, Hsi 7.1 and Hsi 7.2, explained 22.30–24.93% and 14.85–16.79% of phenotypic variation in the two years, respectively. The results from QTL mapping and genetic analysis in both years were partially consistent and complemented each other. Our results provide a foundation for further research on genetic regulation, gene cloning and molecular marker-assisted selection (MAS) for head shape in cabbage.

Bright green of leaf head is an important characteristic in cabbage breeding. Wax-less cabbage shows glossy phenotype on leaf surface, which facilitates the brilliant green cabbage breeding. In this study, we identified a spontaneous glossy mutant g21-3 in cabbage. Genetic analyses showed that its glossy phenotype is controlled by a single recessive gene. Further analysis indicated that the glossy phenotype of g21-3 and a known glossy cabbage mutant 10Q-961 was controlled by a same locus. According to the fine-mapping of glossy-controlled gene in 10Q-961, BoCER1 was identified as a candidate gene which was found to be closely related to the glossy phenotype in g21-3. Sub-cellular localization showed that BoCER1 protein is localized to the endoplasmic reticulum. Sequence analysis revealed that a 252-bp insertion was included in the fourth intron of BoCER1 in g21-3, but not in the wild-type 21-3. The insertion significantly inhibited the expression of BoCER1. A marker designed to distinguish between the BoCER1 alleles in g21-3 and wild-type cabbage co-segregated perfectly with glossy/waxy phenotypes in backcross population, confirming that the insertion mutation of BoCER1 is responsible for the glossy phenotype. The allele-specific marker is effective for marker-assisted selection of the glossy cabbage.

The great majority of terrestrial plants produce epicuticular wax that is used to protect plants from a variety of biotic and abiotic stresses. Cabbage epicuticular wax is a white crystalline compound of various lipids. Wax-less cabbage has the characteristics of lustrous green leaves and beautiful exterior, which facilitates the brilliant green cabbage breeding. CGL-3 is a spontaneous wax-less mutant identified from cabbage. Genetic analysis indicated that the waxy deficiency of the mutant was controlled by a single dominant gene. To clarify the mechanism of the waxy deficiency, fine-mapping and transcriptome analysis of the wax-less gene, BoGL-3, were carried out in this study. The result of fine mapping showed that the wax-less gene, BoGL-3, was delimited in a 33.5-kb interval which is between the flanking marker C08-98 and the end of chromosome 8. Two cDNA libraries, constructed with wax-less cabbage CGL-3 and the wild-type cabbage WT, were sequenced for screening of the target gene BoGL-3. A total of 8340 genes were identified with significant differential expression between CGL-3 and WT. Among these genes, 3187 were up-regulated and 5153 were down-regulated in CGL-3. With homologous analysis, four differential expressed genes related to wax metabolism were obtained. Among these four genes, only Bol018504 is located within the region of fine-mapping. Bol08504 is homologous to CER1, which encodes fatty acid hydroxylase and plays an important role in wax synthesis in Arabidopsis. However, there was no difference of Bol08504 sequence between CGL-3 and WT. We suggested that Bol018504 was regulated by BoGL-3. The suppression of Bol018504 leads to the reduction of wax. These findings will be helpful to reveal the mechanism of the wax metabolism in cabbage and develop lustrous green cabbage germplasm material.

Although the genetics and preliminary mapping of the cabbage yellow-green-leaf mutant YL-1 has been extensively studied, transcriptome profiling associated with the yellow-green-leaf mutant of YL-1 has not been discovered. Positional mapping with two populations showed that the yellow-green-leaf gene ygl-1 is located in a recombination-suppressed genomic region. Then, a bulk segregant RNA-seq (BSR) was applied to identify differentially expressed genes (DEGs) using an F3 population (YL-1 &times, 11-192) and a BC2 population (YL-1 &times, 01-20). Among the 37,286 unique genes, 5730 and 4118 DEGs were detected between the yellow-leaf and normal-leaf pools from the F3 and BC2 populations. BSR analysis with four pools greatly reduced the number of common DEGs from 4924 to 1112. In the ygl-1 gene mapping region with suppressed recombination, 43 common DEGs were identified. Five of the DEGs were related to chloroplasts, including the down-regulated Bo1g087310, Bo1g094360, and Bo1g098630 and the up-regulated Bo1g059170 and Bo1g098440. The Bo1g098440 and Bo1g098630 genes were excluded by qRT-PCR. Hence, we inferred that these three DEGs (Bo1g094360, Bo1g087310, and Bo1g059170) in the mapping interval may be tightly associated with the development of the yellow-green-leaf mutant phenotype.

Bud abortion is the main factor affecting hybrid seeds&rsquo, yield during broccoli cross breeding when using ogura cytoplasmic male sterile (ogu CMS) lines. However, the genes associated with bud abortion are poorly understood. We applied RNA sequencing to analyze the transcriptomes of normal and abortive buds of broccoli maintainer and ogu CMS lines. Functional analysis showed that among the 54,753 annotated unigenes obtained, 74 and 21 differentially expressed genes in common were upregulated and downregulated in ogu CMS abortive buds compared with ogu CMS normal buds, maintainer normal, and abortive buds, respectively. Nineteen of the common differentially expressed genes were enriched by GO terms associated with glycosyl hydrolases, reactive oxygen species scavenging, inhibitor, and protein degradation. Ethylene-responsive transcription factor 115 and transcriptional factor basic helix-loop-helix 137 were significantly upregulated, transcription factors DUO1 and PosF21/RF2a/BZIP34 were downregulated in ogu CMS abortive buds compared with the other groups. Genes related to polygalacturonase metabolism, glycosyl hydrolases, oxidation reduction process, phenylalanine metabolism, and phenylpropanoid biosynthesis were significantly changed in ogu CMS abortive buds. Our results increase our understanding of bud abortion, provide a valuable resource for further functional characterization of ogu CMS during bud abortion, and will aid in future cross breeding of Brassica crops.

Cuticular waxes play important roles in plant protection against various biotic and abiotic environmental stresses. The cuticular wax covering gives normal cabbage a glaucous appearance, but the appearance of waxless mutant is glossy green. Based on the present study, inheritance of the glossy green character of mutant HUAYOU2 follows a simple recessive pattern. Genetic analysis of an F2 population comprising 808 recessive individuals derived from HUAYOU2 (P1, maternal parent) and M36 (P2, paternal parent) revealed that a single recessive locus, BoWax1 (Brassica oleracea Wax 1), controls glossy green trait in B. oleracea. This locus was mapped to a region of 158.5 kb on chromosome C01. Based on nucleotide sequence analysis, Bol013612 was identified as the candidate gene for BoWax1. Sequencing results demonstrated that there is a deletion mutation of two nucleotides in the cDNA of Bol013612 of HUAYOU2, which may account for its glossy green trait. These results lay the foundation for functional analysis of BoWax1 and may accelerate research on wax metabolism in cabbage.

We present here the draft genome sequence of FGL03-6, a race 1 strain of Fusarium oxysporum f. sp. conglutinans , the pathogen causing Fusarium yellows of cabbage. The FGL03-6 genome consists of 414 scaffolds with 61,662,789 bp (GC content, 47.9%) and 9,790 predicted genes.

Background The aerial parts of most land plants are covered with cuticular wax which is important for plants to avoid harmful factors. There is still no cloning study about wax synthesis gene of the alcohol-forming pathway in Brassica species. Results Scanning electron microscopy (SEM) showed that, compared with wild type (WT), wax crystal are severely reduced in both the adaxial and abaxial sides of cabbage (Brassica oleracea L. var. capitata L.) leaves from the LD10GL mutant. Genetic analysis results revealed that the glossy trait of LD10GL is controlled by a single recessive gene, and fine mapping results revealed that the target gene Cgl2 (Cabbage glossy 2) is located within a physical region of 170 kb on chromosome 1. Based on sequence analysis of the genes in the mapped region, the gene designated Bol013612 was speculated to be the candidate gene. Gene Bol013612 is homologous to Arabidopsis CER4, which encodes fatty acyl-coenzyme A reductase. Sequencing identified a single nucleotide substitution at an intron/exon boundary that results in an insertion of six nucleotides in the cDNA of Bol013612 in LD10GL. The phenotypic defect of LD10GL was confirmed by a functional complementation test with Arabidopsis mutant cer4. Conclusions Our results indicated that wax crystals of cabbage mutant LD10GL are severely reduced and mutation of gene Bol013612 causes a glossy phenotype in the LD10GL mutant. Electronic supplementary material The online version of this article doi: (10.1186/s12870-017-1162-8) contains supplementary material, which is available to authorized users.

A major QTL controlling early flowering in broccoli × cabbage was identified by marker analysis and next-generation sequencing, corresponding to GRF6 gene conditioning flowering time in Arabidopsis. Flowering is an important agronomic trait for hybrid production in broccoli and cabbage, but the genetic mechanism underlying this process is unknown. In this study, segregation analysis with BC1P1, BC1P2, F2, and F2:3 populations derived from a cross between two inbred lines “195” (late-flowering) and “93219” (early flowering) suggested that flowering time is a quantitative trait. Next, employing a next-generation sequencing-based whole-genome QTL-seq strategy, we identified a major genomic region harboring a robust flowering time QTL using an F2 mapping population, designated Ef2.1 on cabbage chromosome 2 for early flowering. Ef2.1 was further validated by indel (insertion or deletion) marker-based classical QTL mapping, explaining 51.5% (LOD = 37.67) and 54.0% (LOD = 40.5) of the phenotypic variation in F2 and F2:3 populations, respectively. Combined QTL-seq and classical QTL analysis narrowed down Ef1.1 to a 228-kb genomic region containing 29 genes. A cabbage gene, Bol024659, was identified in this region, which is a homolog of GRF6, a major gene regulating flowering in Arabidopsis, and was designated BolGRF6. qRT-PCR study of the expression level of BolGRF6 revealed significantly higher expression in the early flowering genotypes. Taken together, our results provide support for BolGRF6 as a possible candidate gene for early flowering in the broccoli line 93219. The identified candidate genomic regions and genes may be useful for molecular breeding to improve broccoli and cabbage flowering times.

The cuticular wax covering epidermal cells causes the glaucous appearance in cabbage. As a protective barrier, cuticular wax plays various roles in protection against biotic and abiotic stresses. This is the first gene mapping report of a dominant glossy green cabbage mutant. In the present paper, scanning electron microscopy (SEM) demonstrated that the wax crystals were severely reduced in the mutant, which indicates that the glossy green phenotype is caused by cuticular wax reduction. Genetic analysis revealed that the glossy trait is controlled by a single dominant gene. Through primer screening and fine mapping, the mutant gene BoGL1 (Brassica oleracea glossy 1) was delimited to the end of chromosome C08 by the flanking marker SSRC08–76 at a genetic distance of 0.2 cM. Two genes homologous to CER1 (ECERIFERUM 1), a gene related to wax biosynthesis in Arabidopsis, were located in the mapped region. Expressional analysis revealed that the Bol018504 gene was severely suppressed but that no nucleotide variation was found by sequencing. These results lay the foundation for the functional analysis of BoGL1, and they will accelerate the research on wax metabolism in cabbage.

Cabbage is an economically important vegetable worldwide. Cabbage Fusarium Wilt (CFW) is a destructive disease that results in considerable yield and quality losses in cole crops. The use of CFW-resistant varieties is the most effective strategy to mitigate the effects of CFW. 01-20 is an elite cabbage line with desirable traits and a high combining ability, but it is highly susceptible to CFW. To rapidly transfer a CFW resistance gene into 01-20 plants, we used microspore cultures to develop 230 doubled haploid (DH) lines from a cross between 01-20 (highly susceptible) and 96-100 (highly resistant). One of the generated DH lines (i.e., D134) was highly resistant to CFW and exhibited a phenotypic performance that was similar to that of line 01-20. Therefore, D134 was applied as the resistance donor parent. We generated 24 insertion–deletion markers using whole genome resequencing data for lines 01-20 and 96-100 to analyze the genomic backgrounds of backcross (BC) progenies. Based on the CFW resistance gene FOC1, a simple sequence repeat (SSR) marker (i.e., Frg13) was developed for foreground selections. We screened 240 BC1 individuals and 280 BC2 individuals with these markers and assessed their phenotypic performance. The proportion of recurrent parent genome (PRPG) of the best individuals in BC1 and BC2 were 95.8 and 99.1%. Finally, a best individual designated as YR01-20 was identified from 80 BC2F1 individuals, with homozygous FOC1 allele and genomic background and phenotype almost the same as those of 01-20. Our results may provide a rapid and efficient way of improving elite lines through the combined application of microspore culture, whole-genome background analysis, and disease resistance-specific marker selection. Additionally, the cabbage lines developed in this study represent elite materials useful for the breeding of new CFW-resistant cabbage varieties.