Rape Seedlings Research Articles

Water-assisted dissemination of conidia of the mycoparasite Coniothyrium minitans in soil

A study was conducted to determine water-assisted dissemination of conidia of Coniothyrium minitans (Cm), a mycoparasite of Sclerotinia sclerotiorum (Ss), in four soils (yellow–brown soil, red-clay soil, fluvo-aquic soil and black soil) and one sand. Conidial suspensions (1×107 conidia mL−1) of Cm were applied to sieved (2 mm screen) soil or sand in glass tubes to test vertical dissemination (VD) and in aluminum boxes to test horizontal dissemination (HD) of conidia. Results showed that conidia of Cm could be disseminated with water and spread in soil or sand for 16–20 cm vertically and for 5–10 cm horizontally. The conidial concentration of Cm was logarithmically reduced with the increase in depth of VD or the distance of HD. Dissemination of Cm conidia in sand was better than that in four soils. Potting experiments were done to further understand the potential of water-assisted dissemination of Cm conidia in suppression of Ss carpogenic germination. Results showed that more apothecia were produced by Ss sclerotia located at the soil surface than those at 5 and 10 cm in depth. The minimum Cm concentration for suppression of Ss carpogenic germination was 1000 conidia g−1 soil. Two-season field trials indicated that water-assisted application of Cm was an effective strategy used at the time for transplanting oilseed rape seedlings to suppress Ss carpogenic germination, thereby reducing the primary infection source for sclerotinia diseases of oilseed rape.

Effect of selenium on characteristics of rape chloroplasts modified by cadmium

Selenium appears to be an important protective agent that decreases cadmium-induced toxic effects in animals and plants. The aim of these studies was to investigate the changes of properties of chloroplast membranes obtained from Cd-treated rape seedlings caused by Se additions. Chloroplasts were isolated from leaves of 3-week-old rape plants cultured on Murashige-Skoog media supplied with 2 μM Na 2SeO 4 and/or 400 μM CdCl 2 under in vitro conditions. The following physicochemical characteristics of chloroplasts were chosen as indicators of Se-effects: average size, zeta potential, ultrastructure, lipid and fatty acid composition and fluidity of envelope membrane. The results suggest that Se can partly counterbalance the destructive effects of Cd. This protective action led to an increase of chloroplast size reduced by Cd treatment and rebuilt, to some extent, the chloroplast ultrastructure. Lipid and fatty acid composition of chloroplast envelopes modified by Cd showed a decrease in digalactosyl-diacylglycerol content and an increase of content of monogalactosyl-diacylglycerol and phospholipid fractions, as well as an increase of fatty acid saturation of all lipids studied. The change in fatty acid saturation correlated well with a decrease of membrane fluidity and with a diminishing of absolute values of zeta potential. The presence of selenium in cultured media caused a partial reversal of the detected changes, which was especially visible in properties related to the hydrophobic part of an envelope, i.e. fatty acid saturation and fluidity.

Effects of different NaCl concentration on the antioxidant enzymes in oilseed rape (Brassica napus L.) seedlings

The effects of salt stress on the activity of antioxidant enzymes in oilseed rape seedlings (Brassica napus L.) were studied. The results showed that the relative water content in leaves of oilseed rape seedlings was gradually decreased and the electrical conductivity was increased after 24 h under 0, 100, 150, 200, 250 and 300 mmol L−1 NaCl. The activity of peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) was gradually increased under salt stress. After 24 h, the activity of POD and SOD was both maximal under 200 mmol L−1, but that of CAT was maximal under 150 mmol L−1. Subsequently, the activity of these antioxidant enzymes was all decreased. Quantitative real-time PCR analysis revealed that they were salt-inducible genes and their transcript levels were gradually increased with the increase of salt concentration. As the same as the change of POD and SOD activity, the transcript levels of POD and SOD was most abundant after 24 h treatment with 200 mmol L−1 sodium chloride, but that of CAT was most abundant under 150 mmol L−1. Therefore, these results from above indicated that the expression of POD, SOD and CAT genes was induced by salt (such as NaCl) and their activities were positively correlated with expression of their genes.

Plant availability of boron doped on iron and manganese oxides and its effect on soil acidosis

The objective of this study was to test the availability of the boron from doped oxides to rape ( Brassica napus L.), and the effect of the boron doped oxides on soil acidosis. The soil was treated with goethite, manganite and their boron-containing oxides including iron oxide with adsorbed boron (i.e. ad-B-goethite), iron oxide with occluded boron (i.e. oc-B-goethite), manganese oxide with adsorbed boron (i.e. ad-B-manganite) and manganese oxide with occluded boron (i.e. oc-B-manganite). It was found that the boron content of the soil treated with boron-containing oxides was higher than those in ordinary oxide treatments and in control. Rape seedlings grown on the soil treated with boron-containing oxides took up more boron than seedlings grown on ordinary oxide treatments and the control. There was a significant relationship between boron content in oxides, soil boron content and boron total uptake of the rape. The boron-containing oxides appeared to increase the plant available boron of the soil and therefore promoted boron uptake by the rape. This demonstrated that boron desorbed from oxides used in this study can be an important source of boron for plants in acidic soils. The two kinds of boron-containing oxides were found to be more effective in addressing soil acidosis by increasing soil pH and decreasing soil exchangeable acid than the oxide which was not doped boron. This was especially so for boron-containing manganite. The introduction of the oxides also enhanced soil available nutrient content and promoted rape seedling uptake of nutrients, and therefore promoted the rape growth. Regression analysis of nutrient content of the soil and rape seedling dry weight showed there was a significant positive correlation between the Ca and Mg content of the soil and rape seedling dry weight. Multiple regression results showed only Ca content in the soil significantly influenced rape seedling dry weight. It is surmised that the boron containing oxides provided a pre-condition for the absorption of nutrients, i.e., an environment for plants to better utilize Ca and other elements during seedling growth and therefore promoted rape seedling dry weight.

Plant fitness assessment for wild relatives of insect resistant crops

Risk assessments of new insect-resistant crops will need to estimate the potential for increased weediness of wild crop relatives as a consequence of gene flow. When field experiments are precluded by containment concerns, simulation experiments can identify hazards or measure expected differences between GMOs and parental plants. To measure plant fitness consequences of wild plant protection from Bt-susceptible herbivores, we used topical sprays of bacterial Bacillus thuringiensis larvacide (Bt) on Brassica rapa. Spontaneous crosses between B. rapa and Bt cole crops cannot be precluded, especially if adoption of Bt varieties leads to high exposure. We compared survivorship and seed output of B. rapa that were either protected from or exposed to Bt-susceptible Lepidoptera in the various conditions where hybrids are likely to occur: cultivated (disked) soil, uncultivated agricultural field margins, and nearby non-crop habitats (meadows and ruderal areas). The relative effect of herbivore protection varied among years, habitats, and populations of seedlings. In 2003-2004, Bt sprays did not result in lower herbivory on B. rapa, and plant fitness was not increased. However, in 2004-2006 B. rapa seedlings protected from Bt-susceptible herbivores lived 25% longer, on average, than those that were exposed to these herbivores. In addition, an average B. rapa seedling sprayed with Bt throughout its lifetime was twice as likely to produce siliques and had 251% of the seed output of a seedling exposed to herbivores. The fitness advantage of Bt-based plant protection was apparent in 2004-2005 in half the plants that experienced higher herbivory, and for 2005-2006, was more pronounced in agricultural habitats than in meadows with established, perennial vegetation and less disturbance. Positive effects of Bt-based plant protection and greater fitness in disturbed habitats suggest that crop-wild gene flow may benefit weed populations, and that field tests with herbivore exclusion/addition experiments are feasible alternatives when molecular containment of transgenes restricts field experiments with insect resistant crop-wild hybrids.

Determination of herbicide ZJ0273 residue in rapeseed by radioisotopic tracing method

Residue of herbicide ZJ0273 (propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate) in rapeseed under simulated field conditions was evaluated by radioisotopic tracing method. Radio-HPLC and HPLC–MS analysis revealed that the parent ZJ0273 is the only radioactive residue in rapeseed. The residue of propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)[ phenyl-U- 14C 6]benzylamino)benzoate (RCZJ) in postharvest rapeseed from the rape seedlings ( Brassica napus L.) in red clayey soil (S 1) and in fluvio marine yellow loamy soil (S 2) were 0.67 and 1.24 nmol/plant, respectively, based on the 14C radioactivity and the specific activity of the labelled ZJ0273. The RCZJs in the rapeseed (1 kg) from the seedlings in S 1 and in S 2 were 40.13 and 45.33 nmol, respectively, and the amounts of ZJ0273 in the rapeseed (1 kg) were 16.97 and 19.17 μg. The results suggested that only a trace level of residue of ZJ0273 presents in rapeseed due to the poor root absorption of ZJ0273 and the weak translocation of ZJ0273 from rape leaves.

The root microtubule cytoskeleton and cell cycle analysis through desiccation of Brassica napus seedlings

Desiccation tolerance (DT) of orthodox seeds is reduced upon their germination. The main aim of this study was to estimate the range of rape seedling DT by examining the consequences of desiccation on the distribution, stability and orientation of microtubules in diverse cells. Using different parameters, such as relative water content (RWC), the tetrazolium viability test and electrolyte leakage, it has been demonstrated that a small percentage decrease in relative humidity can cause irreparable changes in membrane permeability, as well as in nuclear structure and microtubule cytoskeleton stability. Seedling root tips survived when exposed to low desiccation stress intensity, but small changes in microtubule behavior were observed. Cortical microtubules formed thick arrays, especially near the plasma membrane. Water loss also resulted in a reduction of the mitotic activity. More rapid desiccation caused microtubule depolymerization. Occasionally, abnormal tubulin aggregates were visible. Cell divisions were not detectable under these conditions. Due to the observable microtubule defects, the hypersensitivity of the microtubule cytoskeleton might be a useful and simple parameter for estimating environmental stress intensity.

Characterization of heavy metal-resistant endophytic bacteria from rape (Brassica napus) roots and their potential in promoting the growth and lead accumulation of rape

Two lead (Pb)-resistant endophytic bacteria were isolated from rape roots grown in heavy metal-contaminated soils and characterized. A pot experiment was conducted for investigating the capability of the two isolates to promote the growth and Pb uptake of rape from Pb-amended soil. The two isolates were identified as Pseudomonas fluorescens G10 and Microbacterium sp. G16 based on the 16S rDNA gene sequence analysis. Strains G10 and G16 exhibited different multiple heavy metal and antibiotic resistance characteristics and increased water-soluble Pb in solution and in Pb-added soil. Root elongation assays demonstrated increases in root elongation of inoculated rape seedlings compared to the control plants. Strain G16 produced indole acetic acid, siderophores and 1-aminocyclopropane-1-carboxylate deaminase. Increases in biomass production and total Pb uptake in the bacteria-inoculated plants were obtained compared to the control. The two strains could colonize the root interior and rhizosphere soil of rape after root inoculation.

Effect of ozonation on polychlorinated biphenyl degradation and on soil physico-chemical properties

The objectives of this study were to investigate the effectiveness of ozone treatment on degradation of polychlorinated biphenyl (PCB) contaminated soils and to observe the subsequent changes in soil physico-chemical properties. Furthermore, the ability of plants to grow on the ozone-treated soils was evaluated. Soils with different physico-chemical characteristics spiked with seven PCB congeners in two different time periods were chosen. Ozonation was more efficient for PCB degradation in freshly spiked soils and the removal efficiency increased with increasing ozonation time. The highest decrease was found in the soil with a lower soil organic matter (SOM) content and a coarser soil structure indicating the substantial effect of soil characteristics on the efficiency of ozonation. The composition of individual PCB congeners changed in all treatments in terms of higher accumulation rate of highly chlorinated biphenyls with a higher ozonation time. Increased mobility of several elements, changes in SOM content and in soil pH were detected after ozonation. Vulnerability of plants to these modifications was documented on rape seedlings. No inhibition in growth during any treatment and predominantly higher concentration of PCB in non-ozonated treatments were observed. Results suggest that this method can present a promising environmental friendly remediation technology for PCB contaminated soils.

Effects of 5-Aminolevulinic Acid on Oilseed Rape Seedling Growth under Herbicide Toxicity Stress

Weeds are one of the major constraints in oilseed Brassica production. Use of effective herbicides to control weeds in the fields is one of the major objectives of agronomists. To improve weed control efficacy and minimize the application costs, complex combinations of 5-aminolevulinic acid (ALA) and a new postemergence herbicide, propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273), were used to investigate their combined effects in relation to seedling growth and development of oilseed rape (Brassica napus cv. ZS 758). Brassica seeds were treated with different concentrations of ZJ0273 [100 (normal dose for rape), 200, 500, and 1000 mg/L] and ALA (0.1, 1, 10, and 50 mg/L). ALA was applied as pre- and post-treatment alone and in combination with ZJ0273. We found that ZJ0273 stress imposed negative effects on rape seedling growth. Shoot fresh weight, shoot length, and root fresh weight were inhibited significantly under ZJ0273 stress, and the rate of decline increased consistently with increased ZJ0273 concentration. Root oxidizability was also inhibited significantly under ZJ0273 stress conditions, and the higher the concentration of the herbicide ZJ0273, the lower the oxidizability. Herbicide ZJ0273 treatment produced a gradual decrease in antioxidant enzymes (peroxidase, superoxide dismutase, and ascorbate peroxidase) and an increase in peroxidation substance (malondialdehyde accumulation). The increase and decrease were consistent with the ZJ0273 dosage. Our results indicated that pre- and post-treatments with a lower dosage of ALA (1 mg/L) improved rape seedling growth and root oxidizability parameters, whereas a higher concentration of ALA (50 mg/L) depressed growth. We also found that plants treated with 1 mg/L ALA produced the highest shoot fresh weights, shoot lengths, root fresh weights, and root oxidizability when the seeds were treated with different concentrations of ZJ0273. Lower dosages of ALA improved the activities of antioxidant enzymes, whereas the highest dosage of ALA increased the accumulation of peroxidation substance. These results indicate that ALA has promotive effects in the recovery of growth and development of rape seedlings under herbicide ZJ0273 toxicity stress.

Evaluation of Australian Brassica napus genotypes for resistance to the downy mildew pathogen, Hyaloperonospora parasitica

Downy mildew, caused by the pathogen Hyaloperonospora parasitica, is a severe disease of oilseed rape (Brassica napus) seedlings in some regions of Australia. Sixty-three cultivars of Australian spring-type oilseed rape were evaluated for their levels of resistance to five isolates of the downy mildew pathogen, using a cotyledon infection test under controlled-environment conditions. A high level of resistance, characterised by the absence of disease symptoms or only the appearance of very sparse sporulation on inoculated cotyledons, was expressed in cvv. Pioneer 45Y77 and Pioneer 46Y78. This is the first study to identify Australian genotypes of oilseed rape highly resistant to H. parasitica. The resistance to H. parasitica identified in this study will not only enable Australian oilseed rape breeders to incorporate resistance to H. parasitica into new cultivars for enhanced resistance to this disease, but will also allow direct deployment of the most highly resistant genotypes identified directly in situations and regions most conducive to the development of severe downy mildew disease.

A novel role for Trichoderma secondary metabolites in the interactions with plants

Secondary metabolites play a pivotal role in the antagonistic activities of some biocontrol species of Trichoderma resulting in the suppression of plant pathogens, but their involvement in complex interactions with plants has not been specifically studied. In this work the major secondary metabolites produced by biocontrol strains of Trichoderma ( T. harzianum strains T22, T39 and A6, and T. atroviride strain P1) have been investigated for their effect on plant growth promotion. An auxin-like activity was observed on etiolated pea ( Pisum sativum) stems treated with harzianolide and 6- n-pentyl-6 H-pyran-2-one (6PP), which also affected the growth of tomato ( Lycopersicum esculentum) and canola ( Brassica napus) seedlings. The ability of these molecules to induce systemic defence responses in planta was also investigated. Tomato and oil-seed rape seedlings were treated with the metabolites and then inoculated with a spore suspension of Botrytis cinerea or Leptosphaeria maculans, respectively. In both cases, a reduction of disease symptoms was observed, particularly on 6PP-treated plants. Moreover an over-expression of pathogenesis-related (PR) proteins was also detected in treated plants. These results clearly indicate that secondary metabolites of Trichoderma spp. may have a role in both plant growth regulation and activation of plant defence responses.

The protective role of selenium in rape seedlings subjected to cadmium stress

The effect of selenium (Se) on rape (Brassica napus) seedlings subjected to cadmium (Cd) stress was studied in vitro by investigating plant growth and changes in fatty acid composition, activity of antioxidative enzymes and DNA methylation pattern. Physiological experiments were carried out on seedlings cultured for 2 weeks on Murashige-Scoog (MS) media with Cd concentrations of 0, 400 and 600 microM, and on corresponding media supplied with Se (2 microM). Exposure to increasing Cd concentrations reduced the fresh weight of the upper part (hypocotyls+cotyledons) of the seedlings more strongly than that of the root system, which was accompanied by higher Cd accumulation in these tissues. In the upper part, Cd exposure led to significant changes in the biochemical parameters: fatty acid unsaturation of plasmalemma decreased, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPOX) diminished and that of ascorbate peroxidase (APX) increased. In contrast, the roots showed an increase in fatty acid unsaturation and in the activity of antioxidative enzymes. In both parts of rape seedlings H(2)O(2) level and lipid peroxidation increased. Se addition to medium considerably reversed the Cd-induced decrease in fresh mass as well as the changes in lipid unsaturation and peroxidation. Se applied separately or in combination with Cd did not significantly affect the activity of antioxidative enzymes in the roots, but diminished it in the upper part. Moreover, the presence of Se in medium prevented changes in the DNA methylation pattern triggered in rape seedlings by high Cd concentrations. Two possible mechanisms for the action of Se were considered: (1) removal of Cd from metabolically active cellular sites, and (2) reduction of oxygen radicals.

Effects of brassinosteroid infiltration prior to cold treatment on ion leakage and pigment contents in rape leaves

The effect of 24-epibrassinolide (BR27) on cold resistance of rape seedlings was studied by ion leakage and photosynthetic pigment degradation measurements. Aqueous solutions of BR27 were injected into cotyledons or primary leaves of rape plants and these plants were incubated at 2 °C or 20 °C. Cold treatment (2 °C) without BR27 injection elevated the membrane permeability in both primary leaves and cotyledons significantly. Surprisingly, injection of leaves with water or 0.467 % aqueous ethanol solution led to a massive increase in membrane permeability after cold stress at 2 °C. The synergistic effect of leaf infiltration and cold on permeability was abolished by 0.05 and 1.00 µM of BR27 in primary leaves and by 1.00 µM of BR27 in cotyledons. On the other hand, BR27 solutions strongly elevated the membrane permeability at 20 °C, while water and ethanol solutions brought about only negligible increases. Water or ethanol infiltrations strongly reduced the leaf contents of chlorophyll (Chl) a, Chl b and carotenoids at 2 °C but less markedly at 20 °C. However, in seedlings exposed to 2 °C pigments content was significantly higher in BR27-treated leaves as compared to water/ethanol control. There were no differences between pigment contents of leaves injected with BR27 solutions or only water/ethanol at 20 °C. The above data strongly support the stress protecting effect of BR27.

Bacterial infection and pre-treatment with 24-epibrassinolide markedly affect the heat emission and membrane permeability of rape cotyledons

Changes in metabolic activity in spring oilseed rape ( Brassica napus L.) seedlings during bacterial infection were determined by measuring heat emission with an isothermal calorimeter. Heat emission was markedly increased in cotyledons infected with the incompatible bacterium Pseudomonas syringae pv. syringae. One day after inoculation, visible signs of necrosis were detected on the infected cotyledons. This indicates that the hypersensitive response had been activated. Heat emission continued to increase as the hypersensitive response progressed, reflecting an increase in the metabolic rate in the infected tissue. With both of the cultivars tested heat emission by infected cotyledons was increased by pre-treatment with BR 27. Membrane permeability as measured by ion leakage also rapidly increased during the first 3 days of infection. In uninfected cotyledons pre-treated with BR 27, membrane permeability was slightly increased. In infected cotyledons not pre-treated with BR 27, both visible necrosis and membrane permeability rapidly increased during the first 2 or 3 days after inoculation. In infected cotyledons pre-treated with BR 27, membrane permeability was significantly reduced by the second or third day after inoculation. This confirms that BR 27 plays a role in preventing damage to plant cell membranes caused by bacterial infection during the hypersensitive response.

Lipoxygenases during Brassica napus seed germination

The peroxidation of polyunsaturated fatty acids is mostly catalyzed by members of the lipoxygenase enzyme family. Lipoxygenase products can be metabolized further in the oxylipin pathway and are known as signalling substances that play a role in plant development as well as in plant responses to wounding and pathogen attack. Apart from accumulating data in model plants like Arabidopsis, information on the relevance of lipid peroxide metabolism in the crop plant oilseed rape is scarce. Thus we aimed to analyze lipoxygenases and oxylipin patterns in seedlings of oilseed rape. RNA isolated from 3 day etiolated seedlings contains mRNAs for at least two different lipoxygenases. These have been cloned as cDNAs and named Bn-Lox-1fl and Bn-Lox-2fl. The protein encoded by Bn-Lox-2fl was identified as a 13-lipoxygenase by expression in Escherichia coli. The Bn-Lox-1fl yielded an inactive protein when expressed in E. coli. Based on Bn-Lox-1fl active site determinants and on sequence homology the Bn-Lox-1fl is most likely a 9-lipoxygenase. Both genes are expressed in light-grown and etiolated cotyledons as well as in leaves. Bn-Lox-2fl protein is more abundant in cotyledons of etiolated seedlings than in cotyledons of green seedlings. Both 13- and 9-lipoxygenase-derived hydroperoxides can be detected during germination. Etiolated seedlings contain more lipoxygenase-derived hydroperoxides in non esterified fatty acids than green seedlings. The 13-lipoxygenase derivatives are 6-8-fold more abundant than the 9-derivatives. Lipoxygenase-derived hydroperoxides in esterified lipids are almost not present during germination. These results suggest that 13-lipoxygenases acting on free fatty acids dominate during B. napus seed germination.

Behavior and fate of chlorpyrifos introduced into soil–crop systems by irrigation

The effect of chlorpyrifos added in irrigation water to a red soil from Central South China on the growth of wheat and oilseed rape seedlings, together with its uptake, was studied in a pot experiment. Addition of chlorpyrifos (1–10 μg g −1) in a single irrigation with distilled water resulted in absorption of chlorpyrifos by wheat (0.257–4.50 μg g −1) and also oilseed rape seedlings (0.249–2.02 μg g −1) during 20 d of plant growth. An initial concentration of chlorpyrifos in soil that is equivalent to or below 10 μg g −1 did not significantly influence the growth of wheat seedlings. Similarly, an initial concentration equivalent to or below 5 μg g −1 did not significantly influence the growth of oilseed rape seedlings. The degradation rate of chlorpyrifos was 1.4–4.2 times larger in oilseed rape rhizosphere soil than in unvegetated soil. The numbers of bacteria and fungi in oilseed rape rhizosphere soil were 3.18 times and 1.84 times larger, respectively, than those in unvegetated soil. This helps to explain the difference in degradation rates obtained.

Effect of Rare Earths on Plants under Supplementary Ultraviolet-B Radiation: II. Effect of Cerium on Antioxidant Defense System in Rape Seedlings under Supplementary Ultraviolet-B Radiation

Effects of cerium (Ce 3+) on membranous protective enzymes in rape seedlings exposed to two levels of enhanced ultraviolet-B radiation (UV-B, 280 ∼ 320 nm) were studied by hydroponics in the laboratory. The results show that the chlorophyll content decreases and membrane permeability increases in the leaves under UV-B irradiation with an intensity of 0.15 and 0.35 W·m −2. The activities of SOD, CAT and POD are first increased and then decreased in leaves exposed to a low level of UV-B radiation. POD activity in leaves exposed to a high level of UV-B radiation is enhanced constantly. The sensitivities of these enzymes to UV-B radiation are SOD > CAT > POD. The injury by UV-B radiation on the functions of protective enzymes is lightened, their ability to scavenge radicals is improved, and the membrane permeability is maintained by Ce. Furthermore, the protective effect of cerium is more obvious in plants exposed to low levels of UV-B radiation than to high levels of it. Accordingly, all results prove that the protective effect of Ce on plants under UV-B radiation is realized through the protective system of plants.

Mini-plot field experiments using seed dressings to control slug damage to oilseed rape

Previous studies have shown that seed dressing with methiocarb or metaldehyde can protect newly emerged oilseed rape seedlings from slug damage. Here, we document two mini-plot field experiments testing these seed dressings. Both metaldehyde and methiocarb significantly reduced slug damage compared with untreated control seeds, but both seed dressings performed less well to the metaldehyde bait pellets. Protection offered by metaldehyde seed dressing was short-lived, whereas methiocarb seed dressings gave protection throughout the 4 weeks duration of both experiments.

Improvement of rape ( Brassica napus) plant growth and cadmium uptake by cadmium-resistant bacteria

This study focuses on the screening of cadmium-resistance bacterial strains from heavy metal-polluted soils to examine their plant growth promotion and cadmium uptake in rape ( Brassica napus). A large number of bacteria were isolated from heavy metal-polluted soil in Nanjing, China. Thirty isolates showing cadmium-resistance on Cd-amended medium were selected and evaluated for their potential to solubilize cadmium carbonate in solution culture. Atomic absorption spectrometer analysis showed variable amounts of water-soluble Cd (ranging from 24 to 117 mg l −1) released by the cadmium-resistant bacterial strains from cadmium carbonate. Qualitative analysis confirmed the presence of indole acetic acid as the auxin in the culture of these cadmium-resistant bacterial strains. Root elongation assay conducted on rape under gnotobiotic conditions demonstrated increases (up to 31%) in root elongation of inoculated rape seedlings compared to the control plants. Based upon cadmium-resistance, bio-activation of CdCO 3 and growth-promoting activity, three isolates were selected for promoting plant growth and uptake of cadmium from cadmium-amended soil in pot experiments. Inoculation with the isolates was found to increase root dry weight (ranging from 8% to 20%) and shoot dry weight (ranging from 6% to 25%) of rape. An increase in cadmium content varying from 16 to 74%, compared to the non-inoculated control, was observed in rape plants cultivated in soil treated with 100 mg Cd kg −1 (as CdCl 2) and inoculated with the isolates. The bacterial isolates were also able to colonize and develop in the rhizosphere soil of rape after root inoculation.