Wild Brassica Species Research Articles

QTL mapping and transcriptome analysis identify novel QTLs and candidate genes in Brassica villosa for quantitative resistance against Sclerotinia sclerotiorum

Key messageNovel QTLs and candidate genes for Sclerotinia-resistance were identified in B. villosa, a wild Brassica species, which represents a new genetic source for improving oilseed rape resistance to SSR.Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, is one of the most destructive diseases in oilseed rape growing regions. To date, there is no effective genetic resistance against S. sclerotiorum in the B. napus germplasm and knowledge of the molecular plant–fungal interaction is also limited. To identify new resistance resources, we screened a set of wild Brassica species and identified B. villosa (BRA1896) with a high level of Sclerotinia-resistance. Two segregating F2 populations for Sclerotinia-resistance, generated by interspecific crosses between the resistant B. villosa (BRA1896) and the wild susceptible B. oleracea (BRA1909) were assessed for Sclerotinia-resistance. Genetic mapping using a 15-k Illumina Infinium SNP-array resulted in a high-density genetic map containing 1,118 SNP markers and spanning a total genetic length of 792.2 cM. QTL analysis revealed seven QTLs explaining 3.8% to 16.5% of phenotypic variance. Intriguingly, RNAseq-based transcriptome analysis identified genes and pathways specific to B. villosa, of which a cluster of five genes encoding putative receptor-like kinases (RLKs) and two pathogenesis-related (PR) proteins are co-localized within a QTL on chromosome C07. Furthermore, transcriptomic analysis revealed enhanced ethylene (ET)-activated signaling in the resistant B. villosa, which is associated with a stronger plant immune response, depressed cell death, and enhanced phytoalexin biosynthesis compared to the susceptible B. oleracea. Our data demonstrates that B. villosa represents a novel and unique genetic source for improving oilseed rape resistance against SSR.

Genetic Variation and Stability Analysis of an Artificially Synthesized Allohexaploid Brassica for Breeding Innovations

Allopolyploids play an essential role in plant evolution and confer apparent advantages on crop growth and breeding compared to low ploidy levels. A doubled haploid (DH) population derived from the cross between two artificially synthesized allohexaploid Brassica was created and self-crossed continuously. Morphological and yield-related traits showed considerable variation among different generations, different families and even within the same families. However, the flowering time, pollen viability and seed yield increased gradually during the selfing process. Ploidy level estimation and karyotyping analysis revealed that this population was chimeras with varied chromosome numbers within an identical plant. Chromosome translocations analysis showed that the B genome was more instable compared to the A and C genomes. The A genome was more prone to chromosome recombination than the C genome. Although some genomic regions were more likely to be duplicated, deleted, or rearranged, a consensus pattern was not shared between different progenies. This research deepened our understanding of the genetic variation of artificially synthesized allohexaploid Brassica. In addition, the allohexaploid Brassica can be used as a bridge to transfer some of the valuable traits blocked by reproductive barriers from wild Brassica species to cultivated species such as cold and drought resistance, etc.

Deconstructing molecular phylogenetic relationship among cultivated and wild Brassica species

Brassica represents an agriculturally important and diverse group of oilseed crops with a long evolutionary history. Molecular markers played an important role in understanding origin and evolution of Brassica species. In the present research, both Single Nucleotide Polymorphisms (SNPs) and Simple Sequence Repeats (SSRs) developed from Brassica juncea L. Czern. were used to find out the phylogenetic relationship between different cultivated and wild Brassica species. A total of 88 SSR and 58 SNP markers were found to be functional across 38 genotypes belonging to ten different taxon groups. The polymorphic markers were able to group the genotypes into three different clusters and showed relatedness among different genomes based on genetic distances. The transferability of these markers serve the purpose of their quick use in cultivar identification, diversity and phylogenetic analysis in those orphan crops species where no or less genomic information is available.

Human-Mediated Land Use Change Drives Intraspecific Plant Trait Variation.

In the Anthropocene, more than three quarters of ice-free land has experienced some form of human-driven habitat modification, with agriculture dominating 40% of the Earth’s surface. This land use change alters the quality, availability, and configuration of habitat resources, affecting the community composition of plants and insects, as well as their interactions with each other. Landscapes dominated by agriculture are known to support a lower abundance and diversity of pollinators and frequently larger populations of key herbivore pests. In turn, insect communities subsidized by agriculture may spill into remaining natural habitats with consequences for wild plants persisting in (semi) natural habitats. Adaptive responses by wild plants may allow them to persist in highly modified landscapes; yet how landscape-mediated variation in insect communities affects wild plant traits related to reproduction and defense remains largely unknown. We synthesize the evidence for plant trait changes across land use gradients and propose potential mechanisms by which landscape-mediated changes in insect communities may be driving these trait changes. Further, we present results from a common garden experiment on three wild Brassica species demonstrating variation in both defensive and reproductive traits along an agricultural land use gradient. Our framework illustrates the potential for plant adaptation under land use change and predicts how defense and reproduction trait expression may shift in low diversity landscapes. We highlight areas of future research into plant population and community effects of land use change.

Identification of Black Rot Resistance in a Wild Brassica Species and Its Potential Transferability to Cauliflower

Black rot is a destructive disease that affects B. oleracea crops, causing significant losses to growers throughout the world. The purpose of this study was to screen out new sources resistant to Xanthomonas campestris pv. campestris race 4 (Xcc4) in 26 cauliflower and six related wild species, and to assess the inheritance of resistance. The results indicate that most of the tested accessions were susceptible or had intermediate resistance, except the Boc4601 (a cauliflower stable inbred line) and PI435896, UNICT5168, and UNICT5169 (wild accessions). Among them, UNICT5169 (Brassica montana) and PI435896 (Brassica balearica) showed the strongest resistance to Xcc4, with significantly lower disease index (DI), area of the infected part (AIP) and proportion of the infected part to the total leaf area (PTL) values. UNICT 5169 was selected as an Xcc4-resistant parent because of its relatively good cross seed-setting rate with cauliflower cultivars. F1 hybrids were successfully produced between this wild resistant accession (UNICT 5169) and one susceptible cauliflower breeding line (Boc3202-4), indicating the potential transferability of this resistance to cauliflower. The results of the symptoms severity evaluation of the F2 population indicate that Xcc4 resistance in UNICT5169 is a quantitative trait, which guides future resistance gene location and black rot resistance breeding.

Methylobacterium, a major component of the culturable bacterial endophyte community of wild Brassica seed.

BackgroundPlants are commonly colonized by a wide diversity of microbial species and the relationships created can range from mutualistic through to parasitic. Microorganisms that typically form symptomless associations with internal plant tissues are termed endophytes. Endophytes associate with most plant species found in natural and managed ecosystems. They are extremely important plant partners that provide improved stress tolerance to the host compared with plants that lack this symbiosis. Plant domestication has reduced endophyte diversity and therefore the wild relatives of many crop species remain untapped reservoirs of beneficial microbes. Brassica species display immense diversity and consequently provide the greatest assortment of products used by humans from a single plant genus important for agriculture, horticulture, bioremediation, medicine, soil conditioners, composting crops, and in the production of edible and industrial oils. Many endophytes are horizontally transmitted, but some can colonize the plant’s reproductive tissues, and this gives these symbionts an efficient mechanism of propagation via plant seed (termed vertical transmission).MethodsThis study surveyed 83 wild and landrace Brassica accessions composed of 14 different species with a worldwide distribution for seed-originating bacterial endophytes. Seed was stringently disinfected, sown within sterile tissue culture pots within a sterile environment and incubated. After approximately 1-month, direct isolation techniques were used to recover bacterial endophytes from roots and shoots of symptomless plants. Bacteria were identified based on the PCR amplification of partial 16S rDNA gene sequences and annotated using the BLASTn program against the NCBI rRNA database. A diversity index was used as a quantitative measure to reflect how many different bacterial species there were in the seed-originating microbial community of the Brassica accessions sampled.ResultsBacterial endophytes were recovered from the majority of the Brassica accessions screened. 16S rDNA gene sequencing identified 19 different bacterial species belonging to three phyla, namely Actinobacteria, Firmicutes and Proteobacteria with the most frequently isolated species being Methylobacterium fujisawaense, Stenotrophomonas rhizophila and Pseudomonas lactis. Methylobacterium was the dominant genus composing 56% of the culturable isolated bacterial community and was common in 77% of accessions possessing culturable bacterial endophytes. Two selected isolates of Methylobacterium significantly promoted plant growth when inoculated into a cultivar of oilseed rape and inhibited the growth of the pathogen Leptosphaeria maculans in dual culture. This is the first report that investigates the seed-originating endophytic microorganisms of wild Brassica species and highlights the Brassica microbiome as a resource for plant growth promoting bacteria and biological control agents.

Lepidium cake as a feedstuff for pigs

The European reliance on imported protein feed for animal feed is not considered sustainable. A way to improve the sustainability of pig production could be by increasing the use of locally produced feedstuff and co-products that are not used for human consumption. Thus, there is a need to explore novel feed resources. Field cress, Lepidium campestre, is a wild Brassica species and is very winter hardy, thus, it can grow even in the northern part of Europe. Currently there is an interest in developing L. campestre for future food (oil) and biodiesel production. Besides, its cake has previously been suggested as a feed source to animals. Therefore, a total of 8 pigs having an initial body weight of 26.5 kg (standard deviation: ± 2.5 kg) were used in a 44-d feeding experiment to evaluate the effect of different inclusion rates of lepidium cake (LC) on palatability, coefficient of total tract apparent digestibility (CTTAD), blood profile, and feeding behavior. A total of 4 diets were formulated: a cereal-based control diet and 3 diets containing 4, 8, and 12% of LC (LC4, LC8, and LC12). The experiment was conducted in change-over design, using 4 diets and 4 periods. Each period consists of 11 d, including 7 d of adaptation followed by 4 d of faeces collection. Fecal samples for CTTAD determinations were collected at d 8, 9, 10, and 11 of each period. Blood samples were collected and analyzed at d 8 of each period. Feeding behavior was evaluated in d 1 and 8 of each period. The result of the study showed that the CTTAD of dry matter, organic matter, crude protein, dietary fiber, non-starch polysaccharides, and gross energy was linearly and quadratically affected by diet (P < 0.001). On the other hand, the CTTAD of ether extract was not affected linearly or quadratically. Eating time was not affected by different inclusion rates of LC, but longer eating time (P < 0.05) was recorded in pigs fed the control diet than those fed different inclusion rates of LC. Eating rate was (P = 0.01) also affected by treatment. Accordingly, greater eating rate was documented in pigs fed diet containing 12% LC than those fed the control diet. Furthermore, pigs eating control feed showed a greater frequency of feeding behaviors (searching, throwing, rooting, and moving feed) than those consuming the diet containing 4% of LC. We can suggest that LC is palatable feed to grower pigs, but the result would indicate that the presence of high total dietary fiber and glucosinolate in the cake reduced its CTTAD and energy value.

GIS assessment of the risk of gene flow from Brassica napus to its wild relatives in China.

Risk of gene flow from canola (Brassica napus) to species of wild relatives was used as an example to evaluate the risk of gene flow of transgenic crops. B. juncea and B. rapa were the most common weedy Brassica species in China, which were both sexually compatible with canola. Data on canola cultivation in China were collected and analyzed using geographic information system (GIS), and the distribution of its wild relatives was predicted by MaxEnt species distribution model. Based on biological and phenological evidence, our results showed that gene flow risk exists in most parts of the country, especially in places with higher richness of wild Brassica species. However, risk in dominant canola cultivation regions is relatively low owing to the reduced distribution density of wild species in these regions. Three regions of higher risk of gene flow had been identified. Risk of gene flow is relatively high in certain areas. China has been assumed to be the original center of B. juncea and B. rapa, and gene flow may lead to negative effects on the conservation of biodiversity of local species. Strategies had been proposed to reduce the possibility of gene flow either by monitoring introgression from crops to wild relatives in the areas of high adoption of the crop or by taking measures to limit the releasing of new crops or varieties in the areas with abundant wild relatives.

Bio-morphological characterization of Mediterranean wild and cultivated Brassica species

Bio-morphological characterization of Mediterranean wild and cultivated <i>Brassica</i> species

Resistance to Sclerotinia sclerotiorum in wild Brassica species and the importance of Sclerotinia subarctica as a Brassica pathogen

Brassica crops are of global importance, with oilseed rape (Brassica napus) accounting for 13% of edible oil production. All Brassica species are susceptible to sclerotinia stem rot caused by Sclerotinia sclerotiorum, a generalist fungal pathogen causing disease in over 400 plant species. Generally, sources of plant resistance result in partial control of the pathogen although some studies have identified wild Brassica species that are highly resistant. The related pathogen S. subarctica has also been reported on Brassica but its aggressiveness in relation to S. sclerotiorum is unknown. In this study, detached leaf and petiole assays were used to identify new sources of resistance to S. sclerotiorum within a wild Brassica ‘C genome’ diversity set. High‐level resistance was observed in B. incana and B. cretica in petiole assays, whilst wild B. oleracea and B. incana lines were the most resistant in leaf assays. A B. bourgeai line showed both partial petiole and leaf resistance. Although there was no correlation between the two assays, resistance in the detached petiole assay was correlated with stem resistance in mature plants. When tested on commercial cultivars of B. napus, B. oleracea and B. rapa, selected isolates of S. subarctica exhibited aggressiveness comparable to S. sclerotiorum indicating it can be a significant pathogen of Brassica. This is the first study to identify B. cretica as a source of resistance to S. sclerotiorum and to report resistance in other wild Brassica species to a UK isolate, hence providing resources for breeding of resistant cultivars suitable for Europe.

Antibiosis resistance against larval cabbage root fly, Delia radicum, in wild Brassica-species

AbstractCabbage root flies (Delia radicum) are a major threat to cabbage production in Western Europe and North America. Host plant resistance is the most promising option in controlling cabbage root fly damage. In a no-choice field test, we evaluated 94 accessions belonging to 16 Brassica-species for antibiosis resistance against the larvae. Thirteen accessions were selected as putatively resistant, which were subsequently re-tested in the greenhouse. The proportion of eclosed flies was introduced as the main parameter to assess antibiosis in the greenhouse, together with other insect and plant parameters. High levels of antibiosis resistance were identified in B. fruticulosa PI663081 and B. spinescens BRA2994, with significantly lower proportions of eclosed flies (1 % of the number of eggs used for infestation) compared to other accessions. Both species are difficult to cross with B. oleracea. Plants with a high level of antibiosis and medium to high tolerance were found in several accessions of other Brassica species (B. villosa BRA2922, B. montana BRA2950, B. hilarionis HRIGU12483, B. macrocarpa BRA2944) which are more amenable for crossing with B. oleracea. Selection of the most resistant plants belonging to these accessions may yield promising candidates for breeding cabbages resistant to Delia radicum.

Seed Coat Microsculpturing Is Related to Genomic Components in Wild Brassica juncea and Sinapis arvensis

It has been reported that wild Brassica and related species are widely distributed across Xinjiang, China, and there has been an argument for species identification. Seed coat microsculpturing (SCM) is known to be an excellent character for taxonomic and evolutionary studies. By identifying collections from Xinjiang, China, and combining SCM pattern, flow cytometry, and genome-specific DNA markers as well as sexual compatibility with known species, this study aimed to detect potential relationships between SCM and genomic types in wild Brassica and related species. Three wild collections were found to be tetraploid with a SCM reticulate pattern similar to B. juncea, and containing A and B genome-specific loci, indicating relatively high sexual compatibility with B. juncea. The others were diploid, carrying S-genome-specific DNA markers, and having relatively high sexual compatibility with Sinapis arvensis. Moreover, their SCM was in a rugose pattern similar to that of S. arvensis. It was suggested that SCM, as a morphological characteristic, can reflect genomic type, and be used to distinguish B-genome species such as B. juncea from the related S. arvensis. The relationship between SCM and genomic type can support taxonomic studies of the wild Brassica species and related species.

ETHNOBOTANICAL USES OF BRASSICACEAE IN SICILY

The Brassicaceae are widely represented in Sicily: some of them have an ethnobotanical interest. In this frame, through interviews to representatives of small rural communities, we aimed to carry out an ethnobotanical survey on wild Brassica species in order to identify their traditional uses and compare the overall data with ethnobotanical literature about Sicily. The results showed that in the island sixty-four species, often linked only to dialect names, are used mainly for food. For example, the bitter back-taste given by some species (Brassica fruticulosa Cyr., B. nigra (L.) Koch, Bunias erucago L., Diplotaxis erucoides DC., D. tenuifolia (L.) DC., Nasturtium officinale (R.) Br., Raphanus raphanistrum L., Sinapis alba L., S. arvensis L., etc.) typifies many traditional dishes. Some others (Brassica rupestris Raf., B. oleracea L., Nasturtium officinale L., Raphanus raphanistrum L.) are used in popular medicine. Characteristic is the use of Matthiola incana L. in folklore manifestations during St. Joseph Day, when flowers are used to decorate horses and cover the unpleasant smell.

IN PROGRESS ACTIVITIES OF THE BRASSICA WORKING GROUP OF THE EUROPEAN COOPERATIVE PROGRAMME FOR PLANT GENETIC RESOURCES (ECPGR)

During Phase VIII (2009-2013) of the ECPGR Programme, its Brassica Working Group (BWG) decided to focus the attention of all members on the priority actions represented by the development of AEGIS (A European Genebank Integrated System), and to characterize collections both of B. rapa, which could be defined as a multicrop species for its multiple utilization, and of wild Brassica species (n=9) distributed in the Mediterranean basin. The activities planned are being carried out by DISPA-University of Catania (UNICT), the Centre for Genetic Resources (CGN), Wageningen, the Institute of Sustainable Agriculture of Cordoba (CSIC-Spain), and N.I. Vavilov Research Institute of Plant Industry (VIR), St Petersburg. The activity plan and first results obtained are presented and discussed.

Genetic regulation of glucoraphanin accumulation in Beneforté® broccoli

Diets rich in broccoli (Brassica oleracea var italica) have been associated with maintenance of cardiovascular health and reduction in risk of cancer. These health benefits have been attributed to glucoraphanin that specifically accumulates in broccoli. The development of broccoli with enhanced concentrations of glucoraphanin may deliver greater health benefits.Three high-glucoraphanin F1 broccoli hybrids were developed in independent programmes through genome introgression from the wild species Brassica villosa. Glucoraphanin and other metabolites were quantified in experimental field trials. Global SNP analyses quantified the differential extent of B. villosa introgressionThe high-glucoraphanin broccoli hybrids contained 2.5–3 times the glucoraphanin content of standard hybrids due to enhanced sulphate assimilation and modifications in sulphur partitioning between sulphur-containing metabolites. All of the high-glucoraphanin hybrids possessed an introgressed B. villosa segment which contained a B. villosa Myb28 allele. Myb28 expression was increased in all of the high-glucoraphanin hybrids. Two high-glucoraphanin hybrids have been commercialised as Beneforté® broccoli.The study illustrates the translation of research on glucosinolate genetics from Arabidopsis to broccoli, the use of wild Brassica species to develop cultivars with potential consumer benefits, and the development of cultivars with contrasting concentrations of glucoraphanin for use in blinded human intervention studies.

Resynthesized lines from domesticated and wild Brassica taxa and their hybrids with B. napus L.: genetic diversity and hybrid yield

Resynthesized (Resyn) Brassica napus L. can be used to broaden the genetic diversity and to develop a heterotic genepool for rapeseed hybrid breeding. Domesticated vegetable types are usually employed as B. oleracea parents. We sought to evaluate the potential of wild species as parents for Resyn lines. Fifteen Resyn lines were derived by crossing wild B. oleracea ssp. oleracea and oilseed B. rapa, and 29 Resyn lines were generated from 10 wild Brassica species (B. bourgaei, B. cretica, B. incana, B. insularis, B. hilarionis, B. macrocarpa, B. montana, B. rupestris, B. taurica, B. villosa). Genetic distances were analyzed with AFLP markers for 71 Resyn lines from wild and domesticated B. oleracea, and compared with 55 winter, spring, vegetable, and Asian B. napus genotypes. The genetic distances clearly showed that Resyn lines with wild species provide a genetic diversity absent from the breeding material or Resyn lines from domesticated species. Forty-two Resyn lines were crossed with one or two winter oilseed rape testers, resulting in 64 hybrids that were grown in one year and four locations in Germany and France. The correlation between hybrid yield and genetic distance was slightly negative (r = −0.29). Most of the hybrids with Resyn lines from wild B. oleracea were lower in yield than hybrids with Resyn lines from domesticated B. oleracea. It is promising that Resyn lines descending from unselected wild B. oleracea accessions produced high-yielding hybrids when crossed with adapted genotypes: these Resyn lines would be suited to develop heterotic pools in hybrid breeding.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-012-2036-y) contains supplementary material, which is available to authorized users.

Molecular Population Genetics of theSRKandSCRSelf-Incompatibility Genes in the Wild Plant SpeciesBrassica cretica(Brassicaceae)

Self-incompatibility (SI) in plants is a classic example of a trait evolving under strong frequency-dependent selection. As a consequence, population genetic theory predicts that the S locus, which controls SI, should maintain numerous alleles, display a high level of nucleotide diversity, and, in structured populations, show a lower level of among-population differentiation compared to neutral loci. Population-level investigations of DNA sequence variation at the S locus have recently been carried out in the genus Arabidopsis, largely confirming results from theoretical models of S-locus evolutionary dynamics, but no comparable studies have been done in wild Brassica species. In this study, we sequenced parts of the S-locus genes SRK and SCR, two tightly linked genes that are directly involved in the determination of SI specificity in samples from four natural populations of the wild species Brassica cretica. The amount and distribution of nucleotide diversity, as well as the frequency spectrum of putative functional haplotypes, observed at the S locus in B. cretica fit very well with expectations from theoretical models, providing strong evidence for frequency-dependent selection acting on the S locus in a wild Brassica species.

The Evolution and Diversification ofS-Locus Haplotypes in the Brassicaceae Family

Self-incompatibility (SI) in the Brassicaceae plant family is controlled by the SRK and SCR genes situated at the S locus. A large number of S haplotypes have been identified, mainly in cultivated species of the Brassica and Raphanus genera, but recently also in wild Arabidopsis species. Here, we used DNA sequences from the SRK and SCR genes of the wild Brassica species Brassica cretica, together with publicly available sequence data from other Brassicaceae species, to investigate the evolutionary relationships among S haplotypes in the Brassicaceae family. The results reveal that wild and cultivated Brassica species have similar levels of SRK diversity, indicating that domestication has had but a minor effect on S-locus diversity in Brassica. Our results also show that a common set of S haplotypes was present in the ancestor of the Brassica and Arabidopsis genera, that only a small number of haplotypes survived in the Brassica lineage after its separation from Arabidopsis, and that diversification within the two Brassica dominance classes occurred after the split between the two lineages. We also found indications that recombination may have occurred between the kinase domain of SRK and the SCR gene in Brassica.

Simple sequence repeats reveal uneven distribution of genetic diversity in chloroplast genomes of Brassica oleracea L. and (n = 9) wild relatives

Diversity in the chloroplast genome of 171 accessions representing the Brassica 'C' (n = 9) genome, including domesticated and wild B. oleracea and nine inter-fertile related wild species, was investigated using six chloroplast SSR (microsatellite) markers. The lack of diversity detected among 105 cultivated and wild accessions of B. oleracea contrasted starkly with that found within its wild relatives. The vast majority of B. oleracea accessions shared a single haplotype, whereas as many as six haplotypes were detected in two wild species, B. villosa Biv. and B. cretica Lam.. The SSRs proved to be highly polymorphic across haplotypes, with calculated genetic diversity values (H) of 0.23-0.87. In total, 23 different haplotypes were detected in C genome species, with an additional five haplotypes detected in B. rapa L. (A genome n = 10) and another in B. nigra L. (B genome, n = 8). The low chloroplast diversity of B. oleracea is not suggestive of multiple domestication events. The predominant B. oleracea haplotype was also common in B. incana Ten. and present in low frequencies in B. villosa, B. macrocarpa Guss, B. rupestris Raf. and B. cretica. The chloroplast SSRs reveal a wealth of diversity within wild Brassica species that will facilitate further evolutionary and phylogeographic studies of this important crop genus.

Local and systemic induced responses to cabbage root fly larvae (Delia radicum) in Brassica nigra and B. oleracea

Feeding by belowground herbivores may induce systemic changes in shoot defence levels that affect the performance of above ground herbivores and higher trophic levels. In this paper two wild Brassica species, B. nigra and B. oleracea were experimentally infested with 10 larvae of the cabbage root fly, Delia radicum. Plant dry masses and glucosinolate levels in shoots, main roots, and fine roots were determined at 3, 7, 12 and 14 days after infestation and compared to those of control plants.