Resistance Of Cabbage Research Articles

Cabbage breeding tools for biotic and abiotic resistance

Cabbage (Brassica oleracea var. capitata) is an important vegetable crop grown globally for its nutritional value and economic importance. However, cabbage production faces significant challenges from various biotic and abiotic stresses, including pests, diseases, and environmental factors such as drought, heat, and salinity. Developing cabbage cultivars with improved resistance to these stresses is crucial for sustainable and productive agriculture. This review article examines the latest breeding tools and approaches used to enhance biotic and abiotic stress resistance in cabbage. It explores traditional breeding methods, marker-assisted selection, genetic engineering, genome editing techniques like CRISPR/Cas9, and emerging technologies such as genomic selection and speed breeding. Furthermore, the article discusses the integration of -omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, to accelerate the development of stress-resistant cabbage cultivars. The study also highlights the importance of incorporating farmer preferences and participatory breeding strategies to ensure the adoption and success of these improved cabbage cultivars.

Fine mapping and identification of the downy mildew resistance gene BoDMR2 in Cabbage (Brassica oleracea L. var. capitata).

Cabbage (Brassica oleracea L. var. capitata) is an important crop within the Brassica oleracea species and is extensively cultivated worldwide. In recent years, outbreaks of downy mildew caused by Hyaloperonospora parasitica have resulted in substantial losses in cabbage production. Despite this, there have been limited studies on genes associated with resistance to downy mildew in cabbage. This study identified sister lines exhibiting significant differences in disease resistance and susceptibility. Using bulked segregant analysis followed by sequencing (BSA-seq) and linkage analysis, the cabbage resistance locus BoDMR2 was accurately mapped to an approximately 300kb interval on chromosome 7. Among the candidate genes identified, several single nucleotide polymorphisms (SNPs) and a 3-bp insertion were found within the conserved domain of the Bo7g117810 gene, encoding a leucine-rich repeat domain protein, in susceptible genotypes. Additionally, real-time quantitative polymerase chain reaction (RT‒qPCR) analysis revealed that the expression level of Bo7g117810 in resistant specimens was 2.5-fold higher than that in susceptible specimens. An insertion‒deletion (InDel) marker was designed based on the identified insertion in susceptible materials, facilitating the identification and selection of downy mildew-resistant cabbage cultivars. This study identifies Bo7g117810 as a potential candidate gene associated with adult-stage resistance to downy mildew in cabbage, supported by observed differences in gene sequence and expression levels. Furthermore, the development of an InDel marker I1-3, based on its mutation, provides valuable resources for breeding resistant cabbage cultivars.

Comparative Metagenomic Analysis Reveals Rhizosphere Microbiome Assembly and Functional Adaptation Changes Caused by Clubroot Disease in Chinese Cabbage.

Clubroot is a major disease and severe threat to Chinese cabbage, and it is caused by the pathogen Plasmodiophora brassicae Woron. This pathogen is an obligate biotrophic protist and can persist in soil in the form of resting spores for more than 18 years, which can easily be transmitted through a number of agents, resulting in significant economic losses to global Chinese cabbage production. Rhizosphere microbiomes play fundamental roles in the occurrence and development of plant diseases. The changes in the rhizosphere microorganisms could reveal the severity of plant diseases and provide the basis for their control. Here, we studied the rhizosphere microbiota after clubroot disease infections with different severities by employing metagenomic sequencing, with the aim of exploring the relationships between plant health, rhizosphere microbial communities, and soil environments; then, we identified potential biomarker microbes of clubroot disease. The results showed that clubroot disease severity significantly affected the microbial community composition and structure of the rhizosphere soil, and microbial functions were also dramatically influenced by it. Four different microbes that had great potential in the biocontrol of clubroot disease were identified from the obtained results; they were the genera Pseudomonas, Gemmatimonas, Sphingomonas, and Nocardioides. Soil pH, organic matter contents, total nitrogen, and cation exchange capacity were the major environmental factors modulating plant microbiome assembly. In addition, microbial environmental information processing was extremely strengthened when the plant was subjected to pathogen invasion, but weakened when the disease became serious. In particular, oxidative phosphorylation and glycerol-1-phosphatase might have critical functions in enhancing Chinese cabbage's resistance to clubroot disease. This work revealed the interactions and potential mechanisms among Chinese cabbage, soil environmental factors, clubroot disease, and microbial community structure and functions, which may provide a novel foundation for further studies using microbiological or metabolic methods to develop disease-resistant cultivation technologies.

Molecular marking in a white cabbage selection for resistance to Alternaria Blight

In the presented study, the polymorphism of SSR loci was studied on the basis of the resistance of white cabbage to alternariosis. This work was carried out in order to identify effective and informative ISSR markers for the identification of donor alleles of resistance to alternariosis in the genotypes of hybrid plants of culture. Of the 20 tested markers, only 3 (PBCESSRJU13, PBCESSRJU6, NI-F02a) demonstrate an allelic difference between the isogenic lines of white cabbage contrasting in resistance to Alternaria Blight. They will become the basis for subsequent studies on the analysis of cleavage in segregating populations and the determination of informative DNA marker systems co-inherited with the sign of resistance of cabbage to alternariosis.

Effects of Xanthomonas campestris pv. campestris on the photosynthesis of cabbage in the early stage of infection

Cabbage is one of the most important cruciferous vegetables. Black rot, caused by Xanthomonas campestris pv. campestris (Xcc) seriously affects cabbage production; therefore, it is important to study the resistance mechanism to black rot in cabbage. In this study, cabbage photosynthetic physiology changes in the early stages of Xcc infection were analyzed using physiological index determination and transcriptome analysis. The results showed that the Xcc infection can lead the chlorophyll degradation and decreased the net photosynthetic rate (Pn), and the decrease in Pn was mainly due to non-stomatal factors. In addition, the maximum photosynthetic efficiency (Fv/Fm), actual photosynthetic efficiency of photosystem II (PSII) gradually decreased, and the OJIP curve tended to be flat, indicating that Xcc infection reduced the activity of the PSII reaction center and affected the chlorophyll fluorescence intensity. Moreover, the primary photochemical reaction of cabbage leaves was damaged, and electron transfer on the PSII receptor side was inhibited after Xcc infection. NADP-GAPDH and FBPase activities in the Calvin cycle decreased after Xcc invasion. Using transcriptome analysis, 173, 77, 63, and 53 differentially expressed genes (DEGs) were enriched in "carbon metabolism", "photosynthesis", "carbon fixation in photosynthetic organisms", and "metabolism of porphyrins and chlorophyll" metabolic processes, respectively. These results suggest that Xcc infection affects cabbage photosynthesis via multiple pathways. Our results provide a theoretical basis for further research on black rot-resistant breeding and cabbage resistance mechanisms.

Transcriptome analysis reveals resistance induced by Benzothiadiazole against soft rot in Chinese cabbage

Soft rot caused by Pectobacterium carotovorum (Pc) is a harmful disease in Brassica rapa, resulting in severe yield loss. Benzothiadiazole (BTH) can improve plant resistance to various pathogens by inducing systemic acquired resistance (SAR) pathway. In this study, susceptible wild type (WT) and resistant mutant sr in Chinese cabbage—both treated with BTH showed high resistance to Pc infection. Transcriptome analysis showed a series of differentially expressed genes (DEGs) involved in the regulation of leucine-rich repeat resistance (LRR) proteins, peroxidase (POD) accumulation, transcription regulatory factors, and other defense response functions. In particular, WRKY75 and PR4 genes were significantly induced by pathogens and BTH in WT and sr. BTH triggered the increase of endogenous SA. In addition, the enhanced activities of phenylalanine ammonia lyase (PAL) and POD promoted the accumulation of lignin after BTH treatment. We inferred that the lignin played significant roles in BTH-induced resistance of Chinese cabbage resistance to Pc. We present the potential molecular mechanism of BTH-induced resistance for soft rot resistance in Chinese cabbage, which provides a basis for further study of the resistance mechanism of Chinese cabbage to soft rot.

Evaluation of cabbage varieties for resistance to clubroot pathogens, Plasmodiophora brassicae woronin in Dhankuta, Nepal

A field experiment was conducted to evaluate the varietal resistance of cabbage against club root disease, Plasmodiophora brassicae Woronin, in a naturally infested field in Sindhuwa, Dhankuta. It was conducted in a randomized complete block design (RCBD) of three replications and seven treatments, viz., T1: Green Coronet, T2: Nepa Green 777, T3: Big Sun 171, T4: Yr Honam, T5: Big Sun 111, T6: Super Green, and T7: Nepa Star. The plant height was comparatively greater in Green Coronet and Super Green in 60 DAT. In contrast, there was no significant difference in the number of leaves. Big Sun 111 and Yr Honam did not show any signs of galling or clubroot, indicating a significantly higher resistance. Despite not being afflicted by clubroot, Nepa star produced less than satisfying results due to black rot and early head decay. The maximum average head weight and marketable cabbage yield were recorded as being highest in Big Sun 111 (2.56 kg) and Yr Honam (2.24 kg). Furthermore, the yield from Big Sun 171 (1.93 kg) and Nepa Green 777 (1.84 kg) was satisfactory, despite the higher PDI (percentage disease index) (40.33%) and (61.04%), respectively. Disease incidence was zero in Big Sun 111, Yr Honam, and Nepa Star. In terms of productivity and disease resistance, Big Sun 111 (160.13 Mt/ha) and Yr Honam (140.51 Mt/ha) provide the best results, which may be beneficial to farmers who face costly and lengthy disease control practices.

Comprehensive analysis of the full-length transcripts and alternative splicing involved in clubroot resistance in Chinese cabbage

Chinese cabbage is an economically important Brassica vegetable worldwide, and clubroot, which is caused by the soil-borne protist plant pathogen Plasmodiophora brassicae is regarded as a destructive disease to Brassica crops. Previous studies on the gene transcripts related to Chinese cabbage resistance to clubroot mainly employed RNA-seq technology, although it cannot provide accurate transcript assembly and structural information. In this study, PacBio RS II SMRT sequencing was used to generate full-length transcriptomes of mixed roots at 0, 2, 5, 8, 13, and 22 days after P. brassicae infection in the clubroot-resistant line DH40R. Overall, 39 376 high-quality isoforms and 26 270 open reading frames (ORFs) were identified from the SMRT sequencing data. Additionally, 426 annotated long noncoding RNAs (lncRNAs), 56 transcription factor (TF) families, 1 883 genes with poly(A) sites and 1 691 alternative splicing (AS) events were identified. Furthermore, 1 201 of the genes had at least one AS event in DH40R. A comparison with RNA-seq data revealed six differentially expressed AS genes (one for disease resistance and five for defensive response) that are potentially involved in P. brassicae resistance. The results of this study provide valuable resources for basic research on clubroot resistance in Chinese cabbage.

Glucosinolates and Biotic Stress Tolerance in Brassicaceae with Emphasis on Cabbage: A Review.

Glucosinolates (GSLs) and GSL-associated genes are receiving increasing attention from molecular biologists due to their multifunctional properties. GSLs are secondary metabolites considered to be highly active in most Brassica species. Their importance has motivated the discovery and functional analysis of the GSLs and GSL hydrolysis products involved in disease development in brassicas and other plants. Comprehensive knowledge of the GSL content of Brassica species and the molecular details of GSL-related genes will help elucidate the molecular control of this plant defense system. This report provides an overview of the current status of knowledge on GSLs, GSL biosynthesis, as well as hydrolysis related genes, and GSL hydrolysis products that regulate fungal, bacterial, and insect resistance in cabbage and other brassicas.

Evaluation of Insecticides for the Management of Diamondback Moth, (Plutella xylostella (L.) (Lepidoptera: Plutellidae) on Cabbage under Field Condition

Diamondback Moth (DBM) is one of the major constraints for the profitable production of cabbage in the country as well as Ambo highlands in particular. The field study was conducted to evaluate the susceptible varietal resistance of cabbage ( Brassica oleracea var.capitata) against diamondback moth (DBM) ( Plutella xylostella ) infestations and damages at the Ambo university farm in a relay cropping (Rain season) in 2019. Varietal resistance was compared with conventional spraying using Randomized complete block design (RCBD) spraying chemical of insecticides at different spray interval. The Cabbage varieties were Copenhagen from local market. Sampling was done by weekly counting of larvae and pupae, and scoring pest damage on six randomly selected plants per plot for 5 weeks from the third week after transplanting. The number of damage and undamaged cabbage heads were counted on all plants per plot at maturity stage. Results showed that sprayed and unsprayed plots had significantly (P<0.05) different numbers of DBM stages (larvae and pupae). The yield losses of cabbage caused by DBM could reach up to more than 80% as several infestations occurred in the field. Due to this problem, farmers in Ambo highlands are preferred to apply the broad spectrum of non-systematic insecticides rather than implementing other pest management strategies. The demand for insecticides in Ambo highlands seems endless until today, but more aggressive. This paper highlighted the possibility of implementing intercropping cabbage with six treatments in reducing pupae and larvae populations of DBM in the polyculture system. The distributions of pupae and larvae population of DBM against the factors of temperature and rainfall also have been addressed in this study. A total of six treatments were indicated, that including Cutter, Trigger, Ethiozenon, Nomax, Fastac and Control which arranged in (RCBD). The result indicated that nonsignificant variations (P<0.05) were observed among the population of pupae and larvae at all seven treatments tested compared with the control. Moreover, pupae and larvae of DBM were negatively correlated with temperature and rainfall factors. The results also showed that a critical period of DBM infestations was detected in the pre-heading stage (< 30 DAT). In terms of performance among treatments, our finding also has shown that Nomax was the best treatment acted as a repellent. Keywords: Diamondback Moth, Management Strategies, (Plutella xylostella ) Insecticide Resistance. DOI: 10.7176/JBAH/11-23-04 Publication date: December 31 st 2021

Genetic Diversity and Population Structure of the Xanthomonas campestris pv. campestris Strains Affecting Cabbages in China Revealed by MLST and Rep-PCR Based Genotyping.

Xanthomonas campestris pv. campestris (Xcc) is the causal agent of black rot for cruciferous vegetables worldwide, especially for the cole crops such as cabbage and cauliflower. Due to the lack of resistant cabbage cultivars, black rot has brought about considerable yield losses in recent years in China. Understanding of the pathogen features is a key step for disease prevention, however, the pathogen diversity, population structure, and virulence are largely unknown. In this study, we studied 50 Xcc strains including 39 Xcc isolates collected from cabbage in 20 regions across China, using multilocus sequence genotyping (MLST), repetitive DNA sequence-based PCR (rep-PCR), and pathogenicity tests. For MLST analysis, a total of 12 allelic profiles (AP) were generated, among which the largest AP was AP1 containing 32 strains. Further cluster analysis of rep-PCR divided all strains into 14 DNA groups, with the largest group DNA I comprising of 34 strains, most of which also belonged to AP1. Inoculation tests showed that the representative Xcc strains collected from diverse regions performed differential virulence against three brassica hosts compared with races 1 and 4. Interestingly, these results indicated that AP1/DNA I was not only the main pathotype in China, but also a novel group that differed from the previously reported type races in both genotype and virulence. To our knowledge, this is the first extensive genetic diversity survey for Xcc strains in China, which provides evidence for cabbage resistance breeding and opens the gate for further cabbage-Xcc interaction studies.

Inheritance of Black Rot Resistance and Development of Molecular Marker Linked to Xcc Races 6 and 7 Resistance in Cabbage.

Black rot, caused by Xanthomonas campestris pv. campestris (Xcc), produces V-shaped chlorotic lesions on the leaves of cabbage (Brassica oleracea var. capitata L.), causing darkened veins and drastically reducing yield and quality. Of the 11 Xcc races identified, races 1, 4, and 6 are predominant globally. In the present study, we aimed to develop a molecular marker linked to black rot resistance against Xcc races 6 and 7. Crossed between black rot-resistant (‘SCNU-C-3470’) and -susceptible (‘SCNU-C-3328’) lines obtained 186 F2 plants. Resistance to Xcc race 6 segregated in a 3:1 (susceptible:resistant) ratio in the F2 population, which is consistent with a monogenic recessive trait. Nucleotide-binding site (NBS) leucine rich repeat (LRR)-encoding resistance (R) genes play a crucial role in plant defenses to various pathogens. The candidate R gene (Bol031422) located on chromosome C08, previously reported by our research group, was cloned and sequenced in resistant and susceptible cabbage lines. The R gene Bol031422 consisted of a single exon with a 3 bp insertion/deletions (InDels), a 292 bp polymorphism (an insertion in the exon of the resistant line relative to the susceptible line) and several single nucleotide polymorphisms (SNPs). Here, we developed the InDel marker BR6-InDel to assess linkage between variation at Bol031422 and resistance to Xcc races 6 and 7. This marker will help cabbage breeders develop cabbage cultivars resistant to Xcc races 6 and 7.

Molecular marking in breeding Brassica oleracea L. for resistance to Xanthomonas campestris pv. campestris

In the presented study, we have studied polymorphism of 30 microsatellite loci in terms of resistance to black rot (Xanthomonas campestris). Three SSR markers (Ol10-C01, Ol11-H06, BoESSR 726) were identified, showing polymorphism in white cabbage forms with contrasting resistance to black rot. Also, part of the F2 breeding material was analyzed using markers Ol10-C01, Ol11-H06. It was found that they reveal all types of allelic state of genes in a segregating population in accordance with the Mendelian rule of segregation, which makes these markers suitable for further use in studies on the basis of cabbage resistance to black rot.

In silico characterization and expression of disease-resistance-related genes within the collinear region of Brassica napus blackleg resistant locus LepR1′ in B. oleracea

Blackleg is a devastating disease of cabbage (C genome), but so far, only a few resistant cabbage lines have been identified, and the resistance-related genes are yet to be identified. In contrast, numerous R loci have been mapped to the A or B genome. High ancestral synteny among Brassicaceae genomes suggest that homologous regions of R loci in the A or B genome may contain functional R gene(s) in the C genome. Here, we investigated the collinear region of a major Brassica napus R locus, LepR1′, in Brassica oleracea to identify genes of putative disease resistance class via comprehensive in silico analysis. The LepR1′ locus is collinear to a 17.29-Mbp region in chromosome C02 of Brassica oleracea and hosted a total of 1,392 genes, and 36 of these genes contained NBS, LRR, TIR, F-box and RLK domains. The expression of these 36 genes was profiled using qRT-PCR in the cotyledons of resistant (SCNU-03) and susceptible (SCNU-59) lines at 0, 6, 24, and 48 h after inoculation with Leptosphaeria maculans isolates 00–100s and 03–02s having the corresponding avirulent gene, AvrLep1. Among these genes, a cluster of 10 genes were differentially expressed. NBS-LRR gene Bo2g131620 had a 45-bp insertion/deletion (indel) mutation in the 3rd intron between resistant and susceptible lines. The higher expression in resistant lines against both isolates and the indel mutation in Bo2g131620 suggest that these genes may have roles in blackleg resistance in cabbage. Mapping and functional analysis will be necessary to validate such a role. Saturating the region with enough markers is recommended during mapping.

Leptosphaeria maculans Alters Glucosinolate Accumulation and Expression of Aliphatic and Indolic Glucosinolate Biosynthesis Genes in Blackleg Disease-Resistant and -Susceptible Cabbage Lines at the Seedling Stage.

The fungal pathogen, Leptosphaeria maculans causes a severe and economically important disease to Brassica crops globally, well-known as blackleg. Besides, the anti-oxidative defense response of glucosinolates to fungal pathogens is widely established. Despite notable importance of glucosinolates in blackleg disease resistance the association of glucosinolate pathway genes in glucosinolate mediated defense response after L. maculans infection remains incompletely understood. The current study was designed to identify glucosinolate-biosynthesis specific genes among the eight selected candidates induced by L. maculans and associated alterations in glucosinolate profiles to explore their roles in blackleg resistance at the seedling stage of cabbage plants. The defense responses of four cabbage inbred lines, two resistant and two susceptible, were investigated using two L. maculans isolates, 03-02s and 00-100s. Pathogen-induced glucosinolate accumulation dynamically changed from two days after inoculation to four days after inoculation. In general, glucosinolate biosynthetic genes were induced at 24 h after inoculation and glucosinolate accumulation enhanced at two days after inoculation. An increase in either aliphatic (GIB, GRA) or indolic (GBS and MGBS) glucosinolates was associated with seedling resistance of cabbage. Pearson correlation showed the enhanced accumulation of MGBS, GBS, GIB, GIV and GRA after the inoculation of fungal isolates was associated with expression of specific genes. Principal component analysis separated two resistant cabbage lines—BN4098 and BN4303 from two susceptible cabbage lines—BN4059 and BN4072 for variable coefficients of disease scores, glucosinolate accumulation and expression levels of genes. Enhanced MGBS content against both fungal isolates, contributing to seedling resistance in two interactions—BN4098 × 03-02s and BN4303 × 00-100s and enhanced GBS content only in BN4098 × 03-02s interaction. Aliphatic GRA took part in resistance of BN4098 × 00-100s interaction whereas aliphatic GIB took part is resistance of BN4098 × 03-02s interaction. Aliphatic GIV accumulated upon BN4098 × 03-02s interaction but GSL-OH-Bol033373 and CYP81F2-Bol026044 showed enhanced expression in BN4303 × 03-02s interaction. The association between the selected candidate genes, corresponding glucosinolates, and seedling resistance broaden the horizon of glucosinolate conciliated defense against L. maculans in cabbage seedlings.

Transcriptomic analysis of resistant and susceptible cabbage lines reveals differential expressions and candidate genes involved in cabbage early responses to black rot.

Cabbage (Brassica oleracea var. capitata) is one of the most important cruciferous leafy vegetable crops and is widely cultivated all over the world. Its yield and quality are often affected by diseases such as cabbage black rot. 2R is a cabbage line that is newly resistant to black rot, which was created by radiation mutagenesis and backcross transfer. However, the underlying molecular bases and mechanisms of early-phase response of different resistant cabbage lines against black rot infections remain unknown. Here, we completed a comprehensive transcriptome profile analysis between resistant (2R) and susceptible (2T) cabbage lines after black rot inoculations. The results showed that the typical V-shaped lesions were found in inoculated plants after 15days, and the symptoms in the susceptible cabbage lines (2T) were significant severe than that of the resistant 2R line. A total of 10,030 differentially expressed genes (DEGs) were identified, of which 384 DEGs were found to overlap in resistant and susceptible cabbage lines after black rot infections, suggesting those DEGs may play more important roles in cabbage early responses to black rot infections. We ranked the expression levels of DEGs among the four comparison sets of resistant and susceptible cabbage lines and, interestingly, found the top ten differential expression genes contained NBS-LRR genes, protein kinase genes and expansin genes. These findings provide a comprehensive differential transcriptome profile between resistant and susceptible cabbage lines and indicate some genes play key roles in the regulation of early response to black rot infections, which will help to understand the molecular resistance of cabbage against these infections.

A time-resolved dual transcriptome analysis reveals the molecular regulating network underlying the compatible/incompatible interactions between cabbage (Brassica oleracea) and Fusarium oxysporum f. sp. conglutinans

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.

In-silico identification and differential expressions of LepR4-syntenic disease resistance related domain containing genes against blackleg causal fungus Leptosphaeria maculans in Brassica oleracea

Blackleg, caused by Leptosphaeria maculans, is a devastating disease for which no resistant (R) gene is reported in cabbage (C-genome). All known R-genes for blackleg in Brassicaceae have been identified in A- or B-genome. However, identification of a few blackleg-resistant cabbage genotypes suggest that C-genome crops may also contain R-genes. Since, there is high ancestral synteny between these three genomes, we reasoned that mining the syntenic regions of known A- or B-genome R-genes may lead to the corresponding functional orthologues in C-genome. Here, we investigated the Brassica napus blackleg resistant-loci LepR4 and identified two syntenic blocks of 9.56 and 1 Mb in chromosomes C03 and C08, respectively, hosting a total of 1137 genes in C- genome. Among these, twelve genes have functional domains such NB-ARC, LRR, CC, TIR, MAP-kinase and S_TKc that have putatively roles in disease resistance. Higher expressions of leucine-rich repeat receptor-like kinase genes Bo3g110840 and Bo3g103150 against two L. maculans isolates in two resistant genotypes and of Serine/Threonine protein kinase genes Bo3g114980 and Bo3g130040 against both isolates in one resistant genotype and against one isolate in both resistant genotypes, respectively suggest their putative roles in conferring resistance to blackleg in cabbage. This approach is auxiliary to conventional mapping based approach and can be replicated for identifying all other A- or B-genome syntenic putative R-genes in C-genome which, upon validation by functional assays, will be helpful in enhancing our understanding and improving blackleg resistance in cabbage.

Inheritance Pattern and Molecular Markers for Resistance to Blackleg Disease in Cabbage.

The inheritance and causal loci for resistance to blackleg, a devastating disease of Brassicaceous crops, are yet to be known in cabbage (Brassica oleracea L.). Here, we report the pattern of inheritance and linked molecular marker for this trait. A segregating BC1 population consisting of 253 plants was raised from resistant and susceptible parents, L29 (♀) and L16 (♂), respectively. Cotyledon resistance bioassay of BC1 population, measured based on a scale of 0–9 at 12 days after inoculation with Leptosphaeria maculans isolate 03–02 s, revealed the segregation of resistance and ratio, indicative of dominant monogenic control of the trait. Investigation of potential polymorphism in the previously identified differentially expressed genes within the collinear region of ‘B. napus blackleg resistant loci Rlm1′ in B. oleracea identified two insertion/deletion (InDel) mutations in the intron and numerous single nucleotide polymorphisms (SNPs) throughout the LRR-RLK gene Bol040029, of which six SNPs in the first exon caused the loss of two LRR domains in the susceptible line. An InDel marker, BLR-C-InDel based on the InDel mutations, and a high resolution melting (HRM) marker, BLR-C-2808 based on the SNP C2808T in the second exon were developed, which predicated the resistance status of the BC1 population with 80.24%, and of 24 commercial inbred lines with 100% detection accuracy. This is the first report of inheritance and molecular markers linked with blackleg resistance in cabbage. This study will enhance our understanding of the trait, and will be helpful in marker assisted breeding aiming at developing resistant cabbage varieties.

Comparative transcriptome analysis of cabbage (Brassica oleracea var. capitata) infected by Plasmodiophora brassicae reveals drastic defense response at secondary infection stage

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.