Brassica Spp Research Articles

Inheritance of root glucosinolate content in canola

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Vital staining of plant cell suspension cultures: evaluation of the phytotoxic activity of the phytotoxins phomalide and destruxin B.

A cell suspension culture assay to determine the phytotoxicity of the fungal toxins phomalide, a host-selective toxin produced by the fungus Phoma lingam (Tode ex Fr.) Desm., perfect stage Leptosphaeria maculans (Desm.) Ces. et de Not., and destruxin B, the major host-selective toxin produced by the fungus Alternaria brassicae (Berk.) Sacc., was carried out with three Brassica spp. It was established that phomalide was significantly less phytotoxic to Cutlass (Brassica juncea), the cultivar resistant to L. maculans, than to Westar (B. napus), the cultivar susceptible to L. maculans, at concentrations ≤2×10-5 M. Similar to phomalide, destruxin B, at concentrations ≤5×10-5 M, decreased the viability of cells of the cultivar resistant to A. brassicae (Ochre, Sinapis alba) less than the viability of cells of the susceptible cultivar (Westar, B. napus). Considering the high selectivity of phomalide and its direct correlation with plant disease resistance, phomalide may have great potential application in breeding programs screening/selecting for blackleg resistance in brassicas.

Cloning, characterization and chromosomal location of three genes encoding host-cell-wall-degrading enzymes in Leptosphaeria maculans, a fungal pathogen of Brassica spp.

The ascomycete, Leptosphaeria maculans, causes blackleg disease of oilseed Brassica spp. such as canola ( Brassica napus). We have cloned a gene encoding endopolygalacturonase, pg1, and two genes encoding cellulases, cel1 and cel2, in L. maculans. These genes are not clustered in the genome, as they are located on different chromosomes. The deduced amino acid sequences of all three genes predict an N-terminal signal sequence, as is common for secreted fungal enzymes that degrade plant cell walls. The endopolygalacturonase encoded by pg1 shows the highest similarity (54% amino acid identity) to endopolygalacturonase 4 from Botrytis cinerea. Both cel1 and cel2 appear to encode cellobiohydrolase, and neither gene encodes a recognizable cellulose-binding domain or linker region. Transcription of pg1 is induced in cultures containing 1% polygalacturonic acid or pectin, and cel1 is induced in 1% cellulose or carboxymethylcellulose, as shown by Northern analysis. Glucose represses the induction of cel1 caused by cellulose and carboxymethylcellulose, but does affect transcription of pg1. Transcription of cel2 (but not cel1 or pg1) is detectable during infection of B. napus and B. juncea cotyledons and leaves using reverse transcription-PCR.

Characterisation of a cyanide hydratase gene in the phytopathogenic fungus Leptosphaeria maculans.

A gene encoding a cyanide hydratase was cloned from an aggressive isolate of Leptosphaeria maculans, the fungus which causes blackleg disease of oilseed Brassica spp. This enzyme catalyses the breakdown of hydrogen cyanide to a less toxic compound, formamide. The predicted amino acid sequence of cyanide hydratase in L. maculans is 77% and 82% identical to cyanide hydratases from two other ascomycetes, Gloeocercospora sorghi and Fusarium lateritium, respectively. The gene is present as a single copy in the L. maculans genome, in both aggressive and non-aggressive isolates, although there is a restriction fragment length polymorphism between these two isolate groups for this gene. The cyanide hydratase promoter contains four putative target sites for GATA transcription factors, proteins that regulate nitrogen metabolism and other processes. Transcription of cyanide hydratase in an aggressive L. maculans isolate is induced strongly by potassium cyanide. Transcription of the gene is detectable in cotyledons of Brassica juncea and B. napus during infection. L. maculans can utilise the reaction product, formamide, as a sole source of nitrogen.

In vitro selection and biochemical characterisation of zinc and manganese adapted callus lines in Brassica spp.

Zinc- and manganese-tolerant callus lines of Brassica campestris var. M27 and Brassica juncea L. var. Pusabold were developed on Murashige and Skoog (MS) medium supplemented with 0.5 mg l −1 6-benzyladenine (BA), 2.0 mg l −1 1-naphthaleneacetic acid (NAA) and 0.24 mM zinc or 0.80 mM manganese. Shoot bud regeneration was achieved from both tolerant and non-tolerant calluses on MS medium supplemented with 1.0 mg l −1 BA and 0.1 mg l −1 NAA within 4 weeks of subculture. Standard growth parameters such as fresh and dry weight of callus, growth tolerance index, enzyme activity (peroxidase, catalase and acid phosphatase) and metal uptake were used as indicators of zinc and manganese tolerance. Measurements as early as 2 weeks after the beginning of the treatments did not yield consistent results. However, growth tolerance index in the 4 weeks after the beginning of treatments yielded significant differences among the non-tolerant and tolerant calluses. The regenerated shoots were rooted on half-strength MS basal salts supplemented with 2% sucrose but devoid of growth regulator. The regenerated plants from tolerant callus lines were capable of growing in vitro in the presence of 0.24 mM zinc or 0.80 mM manganese. This may help in the selection and characterisation of heavy metal tolerance in plants for breeding programmes.

Pollen-stigma adhesion in Brassica spp involves SLG and SLR1 glycoproteins.

The adhesion of pollen grains to the stigma is the first step of pollination in flowering plants. During this step, stigmas discriminate between pollen grains that can and cannot be permitted to effect fertilization. This selection is operated by various constituents of the cell walls of both partners. Several genes structurally related to the self-incompatibility system that prevents self-pollination in Brassica spp are known to target their products into the stigma cell wall. We proposed previously that one of these genes, the one encoding the S locus glycoprotein (SLG)-like receptor 1 (SLR1), which is coexpressed with that encoding SLG, may participate in pollen-stigma adhesion. Here, we exploit a biomechanical assay to measure the pollen adhesion force and show that it is reduced both by transgenic suppression of SLR1 expression and by pretreatment of wild-type stigmas with anti-SLR1 antibodies, anti-SLG antibodies, or pollen coat-protein extracts. Our results indicate a common adhesive function for the SLR1 and SLG proteins in the pollination process.

Pollen-Stigma Adhesion in Brassica spp Involves SLG and SLR1 Glycoproteins

Pollen-Stigma Adhesion in Brassica spp Involves SLG and SLR1 Glycoproteins

Nondestructive Assessment of Sinapic Acid Esters in Brassica Species: II. Evaluation of Germplasm and Identification of Phenotypes with Reduced Levels

The seed of Brassica spp. contain high levels of sinapic acid esters (SAE). Because of their antiquality nature, the presence of SAE limits the use of Brassica meal as a source of high‐quality protein. The objective of this study was to search for material with reduced SAE content in Brassica spp. A collection of 1487 accessions of 21 species of Brassica and a set of 1361 samples of breeding material of rapeseed (B. napus L.) were analyzed for SAE content by using a previously calibrated near infrared reflectance spectroscopy (NIRS) instrument. The accessions of the germplasm collection showed an average SAE content of 9.4 g kg−1, ranging from 1.7 g kg−1 in an entry of B. tournefortii Gouan to 15.5 g kg−1 in an entry of B. carinata A. Braun. Low levels of SAE were found in B. barrelieri (L.) Janka, B. oxyrrhina Coss., B. souliei (Batt.) Batt., and especially in B. tournefortii, with an average SAE content of 4.1 g kg−1 in 31 accessions. Breeding material of B. napus ranged from 5.0 to 17.7 g kg−1. The samples with the lowest SAE content from both the germplasm collection (n = 112) and the breeding material (n = 75) were further analyzed by the laboratory reference method, with the low levels being confirmed. The SAE content was positively correlated with oil content, and negatively correlated with protein and glucosinolate contents. Because of the observed correlations, simultaneous selection for low SAE, low glucosinolate and high oil contents should be performed. The use of B. tournefortii germplasm having low SAE content in breeding programs can potentially reduce these compounds in cultivated Brassica oilseeds.

Inhibition of Fungal Growth by Macerated Plant Tissues in a Closed Environment

The U.S. Clean Air Act bans the use of methyl bromide after 2001. Consequently, the development of alternative methods for control of soilborne pathogens is imperative. One alternative is to exploit the pesticidal properties of macerated tissues of Brassica spp. This study tested the potential of several Brassica spp. for control of fungal pathogens. Pythium ultimum Trow or Rhizoctonia solani Kühn plugs on potato-dextrose agar on petri dishes were sealed in 500-ml glass jars (at 22 °C) containing macerated leaves (10 g) from one of six Brassica spp. Radial growth was measured 24, 48, and 72 h after inoculation. Indian mustard (B. juncea) was the most suppressive, followed by `Florida Broadleaf' mustard (B. juncea). Volatile compounds in the jars were sampled with a solid-phase microextraction device (SPME) and identified by gas chromatography-mass spectrometry (GC-MS). Allyl isothiocyanate (AITC) comprised over 90% of the total volatiles measured from Indian mustard and `Florida Broadleaf' mustard. Isothiocyanates were detected in jars with all plants except broccoli. (Z)-3-hexenyl acetate was emitted by all plants and was the predominant volatile of `Premium Crop' broccoli (B. oleracea L. var. italica), `Michihili Jade Pagoda' Chinese cabbage (B. pekinensis), `Charmant' cabbage (B. oleracea L. var. capitata), and `Blue Scotch Curled' kale (B. oleracea L. var. viridis). To assess the influence of AITC on radial growth of P. ultimum and R. solani, AITC was added to jars to give headspace concentrations of 0.10, 0.20, and 0.30 mg·L–1 (mass of AITC per volume of headspace). Growth of both fungi was inhibited by 0.10 mg·L–1 AITC. 0.20 mg·L–1 AITC was fungicidal to P. ultimum although the highest AITC level tested (0.30 mg·L–1) did not terminate R. solani growth. These results indicate that residues from some Brassica spp. may be a viable part of a soilborne pest control strategy.

Quantitative karyotyping of three diploid Brassica species by imaging methods and localization of 45s rDNA loci on the identified chromosomes

Chromosomes of the three diploid Brassica species, B. rapa (AA), B. nigra (BB) and B. oleracea (CC), were identified based on their morphological characteristics, especially on the condensation pattern appearing at the somatic pro-metaphase stage. The morphological features of the pro-metaphase chromosomes of the three Brassica spp. were quantified by imaging methods using chromosome image analyzing system II (CHIAS 2). As a result, quantitative chromosome maps or idiograms of the three diploid Brassica spp. were developed. The fluorescence in situ hybridization (FISH) method revealed the location of 45s rDNA (the 26s-5.8s-18s ribosomal RNA gene cluster) on the chromosomes involved. The number of 45s rDNA loci in the B. rapa, B. nigra and B. oleracea are five, three and two, respectively. The loci detected were systematically mapped on the idiograms of the three Brassica spp.

Genetic variation among field isolates of Pyrenopeziza brassicae

Amplified fragment length polymorphism (AFLP) markers were used to determine genetic diversity and population structure of Pyrenopeziza brassicae, the causal agent of light leaf spot of Brassica spp. Fungal isolates were sampled from six regions in the UK, one region in Germany and one region in France. A high level of genetic diversity was found (HT = 58%), with most variation attributed to within regions (HS = 43%), which suggests that sexual reproduction is frequent. FST values suggested significant population differentiation between England and the continent, but not between Scotland and England and Scotland and the continent. Overall, a moderate but significant level of regional differentiation was found (FST = 16 ± 4.0). There was no correlation between FST values and distance, indicating that long‐distance dispersal by natural factors does not occur at high frequencies. However, the lack of differentiation among populations from Aberdeen, Winchester and Cambridge suggests that seed transmission or other artificial methods of dispersal may be important.

Long-term Storage and Cryopreservation of Desiccated Microspore-derived Embryos in Brassica spp.

Microspore-derived embryos of Brassica napus were cryopreserved in liquid nitrogen (LN) after desiccation treatment. Desiccated embryos which were directly immersed in LN converted to plantlets without any decrease in their viability. In contrast, non-desiccated embryos lost their viability after cryopreservation. The longevity and viability of the desiccated embryos of B. campestris were examined under several storage conditions. Survival rates of the embryos were affected by temperature of storage. Lower temperature conditions prolonged their viability. Storage up to 3 years at -80°C did not affect the plant conversion ability of desiccated embryos. These results suggest that naked desiccated embryos of Brassica spp. could be stored for a long period at lower-temperature.

Interactive Effects of Light and CO2 on Photosynthesis and Growth of Brassica spp.

Long- and short-term physiological responses of pak choi (Chinese cabbage, Brassica campestris cv. `Hypro') to elevated CO2 and light environments were evaluated in the series of growth chamber experiments. Plants were grown hydroponically (Nutrient Film Technique) at 25/18°C (day/night) temperature, a 16-h photoperiod, and at three CO2 levels (350, 700, 1400 ppm) and two light levels (200 and 400 μmol·m–2·s–1 PPFD). Relative to 350-ppm CO2 treatment, the final total plant dry mass in low light increased by 37% and 38% at 700 and 1400 ppm CO2, respectively. In high light the increase was 7% and 13% at 700 and 1400 ppm CO2, respectively. Light response curves showed a positive CO2 effect on light compensation point, a slight increase in quantum yield and increase in maximum Pn rates at elevated CO2. Carbon dioxide response curves (measured at saturating PPFD of 1600 μmol·m–2·s–1) showed no effect of growth light treatment on the CO2 compensation point, but a 20% to 30% higher maximum Pn rate at saturating CO2 in plants grown at the higher light level. Overall, the highest Pn rates and the highest plant dry mass at final harvest were found in plants grown at the 400 μmol·m–2·s–1 PPFD and 1400 ppm CO2. Relative beneficial CO2 effects, however, were the most pronounced in low light conditions.

Toxicity of Zinc and Copper to Brassica Species: Implications for Phytoremediation

The toxicity of Zn and Cu in three species from the genus Brassica was examined to determine if these plants showed sufficient tolerance and metal accumulation to be used to phytoremediate a site contaminated with these two heavy metals. Hydroponically grown 12-d-old plants of Brassica juncea, B. rapa, and B. napus were grown for an additional 14 d in the presence of either elevated Zn (6.5 mg L{sup {minus}1}), Cu (0.32 mg L{sup {minus}1}), or Zn+Cu to quantify the toxic effects of these metals on several different growth parameters. With few exceptions, both root and shoot dry weight for all three species decreased significantly in the presence of heavy metals. Cu inhibited lateral root elongation in B. rapa, B. napus, and, to a lesser extent, B. juncea, while Zn tended to decrease only lateral root diameter. Both metals reduced shoot Fe and Mn concentrations in all three Brassica spp. to levels associated with Fe and Mn deficiencies. These deficiencies, however, did not correlate with observed patterns of leaf chlorosis. Nonetheless, heavy metal-induced inhibition of Fe and Mn accumulation may have been a significant factor in reducing plant growth. In terms of heavy metal removal, the Brassica spp, were more effectivemore » at removing Zn from the nutrient solution than Cu. The extent of Zn and Cu removal was reduced in the presence of both metals, as compared to the single heavy metal treatments. The implications of these results for phytoremediation are discussed. 20 refs., 6 figs., 1 tab.« less

Ultrastructural Changes in Brassica Leaves Caused by Alternaria brassicae and Destruxin B

Alternaria blight in Brassica spp (caused by Alternaria brassicae) is characterized by dark brown to blackish necrotic lesions surrounded by chlorotic areas on the leaves. Similar chlorotic lesions were mimicked by a chlorotic toxin (destruxin B) purified from the culture filtrate. Ultrastructural studies were performed to study and compare the changes caused by A. brassicae inoculation in vivo and its host selective toxin under in vitro conditions. Electron microscopy of healthy, chlorotic and necrotic portions of B. campestris leaves naturally infected with A. brassicae revealed considerable differences at ultrastructural level. The necrotic lesions showed plasmolysis with total disruption of cell organelles. The chlorotic lesions had normal plasma membrane but swollen mitochondria with reduced number of cristae and vesiculation of the envelope. Chloroplasts showed degeneration of granal fretwork with an increase in the number of plastoglobuli. Chlorotic lesions due to foliar application of destruxin B induced indentical canges in leaves.

Food, medicinal and other plants from the 15th century drains of Paisley Abbey, Scotland

Plant remains from the 15th century drains at Paisley Abbey, Scotland include medicinal plants which may have grown in the abbey's physic garden. They are Chelidonium majus, Conium maculatum, Euphorbia lathyris, and Papaver somniferum. Plants with both medicinal and culinary uses are Rumex pseudoalpinus and cf Armoracia rusticana. Other vegetables are represented by Allium sp. and Brassica spp. Malus domestica and Prunus domestica ssp. insititia would have been grown in the abbey's orchard. Juglans regia, represented by nut and wood fragments, was either grown in the orchard or imported. Ficus carica was certainly imported as dried fruit from the Mediterranean region. Myristica fragrans as mace came from Indonesia. Locally grown plants are Avena strigosa, Hordeum, Triticum/Secale, Linum usitatissimum and the dye plant Reseda luteola. It is known that spices and other foodstuffs were purchased at fairs at Berry, Bruges and Antwerp and imported into Scotland at the end of the 15th century.

Synthesis of hexaploid (AABBCC) somatic hybrids: a bridging material for transfer of ‘tour’ cytoplasmic male sterility to different Brassica species

Most of the alloplasmic cytoplasmic male sterility (CMS) systems are known to be associated with a number of floral abnormalities that result from nuclear-cytoplasmic incompatibilities. One such system, 'tour', which is derived from Brassica tournefortii, induces additional floral abnormalities and causes chlorosis in Brassica spp. While the restorer for this CMS has been reported to be present in B. napus, in B. juncea, where the abnormalities are more pronounced, no restorer has yet been identified. Rectification of these floral abnormalities through mitochondrial recombinations and chloroplast replacement might result in the improvement of this CMS system. As organelle recombinations can possibly be achieved only by somatic cell hybridization, fusion experiments were carried out between hygromycin-resistant B. juncea AABB carrying 'tour' cytoplasm and phosphinotricin-resistant, normal B. oleracea CC to generate AABBCC hexaploid somatic hybrids. The presence of selectable marker genes facilitated the selection of hybrids in large numbers. The resulting hybrids showed wide variation in floral morphology and organelle composition. Regenerants with normal, male-sterile flowers having recombinant 'tour'-or 'oleracea'-type mitochondria and 'oleracea'-type chloroplasts were obtained. Hybrids with male-fertile flowers were also obtained that had recombined 'tour' mitochondria. The AABBCC hexaploid hybrids synthesized in the present study were successfully utilized as a bridging material for transferring variability in the organelle genome simultaneously to all the digenomic Brassica species, and all of these hybrids are now being stabilized through repeated backcrosses to the allopolyploid crop brassicas.

Formation of nodular structures on the non-legumes Brassica napus, B. campestris, B. juncea and Arabidopsis thaliana with Bradyrhizobium and Rhizobium isolated from Parasponia spp. or legumes grown in tropical soils

Strains of Bradyrhizobium formed nodule-like structures on Arabidopsis and species of Brassica in pots with sandvermiculite and in glass tubes on a nitrogen-free mineral salts agar. Broad-host-range Rhizobium strains NGR234 from Lablab purpureus and NGR76 from Phaseolus vulgaris formed similar nodule-like structures on Brassica spp. The size of these structures on plants in pots were large, often reaching 10 mm in diameter. The frequency of inoculated Brassica plants in pots with nodule-like structures was 25–50%, depending on the inoculum strain. The inheritable nature of factors involved in the formation of the nodule-like structures was demonstrated when the structures occurred on 100% of inoculated B. napus seedlings derived from plants with the nodule-like structures. Nodule-like structures occurred without, but not with, the application of a cellulase-pectolyase-PEG treatment to the roots. Attempts to isolate Bradyrhizobium or Rhizobium from the nodule-like structures failed. Internal infection of these structures could not be detected using either the light or electron microscope. The inoculum strains of root-nodule bacteria were detected in high numbers in the rhizosphere of plants 5 months after inoculation. On agar plates bacterial colonies could be seen, with undiminished growth, over the surface of the agar extending to the root surface. However, ground root tissue of Brassica was toxic to Bradyrhizobium strains. This suggested that Bradyrhizobium strains would not survive after infecting the roots of Brassica spp. Nitrogen fixation was associated with high rhizosphere populations of Azospirillum and not with Bradyrhizobium induced nodule structures of Brassica spp.

Molecular aspects of self-incompatibility in flowering plants.

It is seven years since the first reports of cDNAs encoding pistil glycoproteins that segregated with particular S-alleles. During this time, the S-glycoproteins of the Solanaceae have been identified as RNases. This enzymatic activity relies on the presence of histidine residues at the putative active site of the RNase, and these are conserved in all S-glycoproteins so far characterized. The proteins also contain "hypervariable" regions that may have some role in allelic specificity. It is particularly interesting that putative S-glycoproteins from Japanese pear, which is from a different family, the Rosaceae, are also RNases. To counter the temptation to extrapolate to other families with gametophytic self-incompatibility, there is evidence that in another family, the Papaveraceae, poppy S-glycoproteins are not RNases. The current evidence is consistent with a process in which the S-RNase moves into the incompatible pollen tube and degrades RNA, including rRNA. As rRNA genes are not transcribed in pollen, the resulting degradation would lead to the death of the cell. But still we are left with some important gaps in our knowledge. How does the S-RNase move across the wall and membrane and into the pollen tube? How is the specificity of the interaction controlled? What is the mechanism of signal transduction? A major bottleneck in unraveling the story is understanding the nature of the S-locus product in pollen. Is it related to the stylar S-locus product or is it the product of a different gene in the same locus? Each question underlines the sketchiness of our knowledge of many plant processes that are not specific to pollination, but that we need to understand if we are to work out the details of self-incompatibility. For example, we have a very incomplete understanding of cell wall synthesis generally and pollen wall synthesis in particular. How do macronutrients move through cell walls to the cytoplasm of cells generally and pollen tubes in particular? What is the nature of the receptor-ligand interaction in plant cells generally and pollen tubes in particular? A similar range of questions and gaps in our knowledge exist in the sporophytic system, exemplified by studies in Brassica spp. In this case, we have no known enzymatic or other function for the stigmatic S-glycoproteins. We do, however, know that the S-locus in Brassica includes at least two genes, one encoding a S-glycoprotein and the other encoding a protein kinase.(ABSTRACT TRUNCATED AT 400 WORDS)

Seed Germination Response for Eleven Forage Cultivars of Brassica to Temperature

AbstractSlow germination and poor seedling vigor limit stand establishment of forage Brassica spp. Soil temperature is a major factor influencing both processes. Temperature effects on germination of 11 forage brassica cultivars, comprised of three species plus one hybrid, were studied in an incubator. The species and cultivars tested were turnip (B. rapa L.): Civastro‐R, Polaris, Purple Top, Stubble, and Forage Star; rape (B. napus L.): Emerald, Fodder, and Dwarf Essex; kale (B. oleracea L.): Premier, and Marls Kestral; and the turnip × Chinese cabbage hybrid [B. rapa L. × B. pekinensis (Lovr.) Rupr.]: Tyfon. Germination studies were conducted in the dark at 10 constant temperatures (0, 2, 5, 10, 15, 20, 30, 35, 40, and 50°C). Number of seeds germinated were counted on Day 4 and 14 after planting. Cultivars differed significantly (P ≤ 0.001) for percentage germination on both day 4 and 14 at all temperature treatments except 2 and 40°C. Under the cool temperatures (5 and 10°C), Civastro‐R, Polaris, Purple Top, and Stubble were the earliest germinating cultivars. At the 40°C temperature regime, Marls Kestral initiated germination earlier than that of the other cultivars, but total germination was highest for Polaris. The cultivars Civastro‐R, Polaris, Purple Top, and Stubble could serve as potential parents of a new cultivar because of their ability to germinate rapidly over a wide range of temperatures.