Roots Of Oilseed Rape Research Articles

Enhanced Plant Growth Through Composite Inoculation of Phosphate-Solubilizing Bacteria: Insights from Plate and Soil Experiments

Excessive application of phosphorus (P) fertilizers does not alleviate P deficiency in soils and may cause water eutrophication. The available P in acidic soils is bound to minerals, such as iron and aluminum, in forms that are difficult to utilize by plants. The low availability of P is detrimental to soil health and crop growth. To address the P imbalance in the soil, different bioremediation techniques, such as phosphate-solubilizing bacteria (PSB) application, have been employed. However, the systematic analysis of the effects of composite inoculation of PSB on crops remains elusive. In this study, the effects of composite-inoculated PSB on plant growth were systematically evaluated by two scales: plate experiment and soil test. This study employed six different strains of PSB including Lelliottia amnigena 1-1 (A), Kluyvera intermedia 1-2 (B), Pseudomonas tolaasii 1-6 (C), Burkholderia cepacia 2-5 (D), Pseudomonas frederiksbergensis 2-11 (E), and Pseudomonas rhodesiae 2-47 (F). Among the 57 different combinations of these strains, four combinations (AE, AF, ADF, and AEF) indicated higher phosphate-solubilizing abilities than the single strains. These combinations were used for subsequent experiments. The plate experiment revealed that composite strains were more effective than single strains in promoting the growth and development of seedlings and roots of oilseed rape. Furthermore, AE, AF, and AEF combinations indicated excellent growth-promoting effects. Moreover, the soil test revealed that the composite inoculation of AE and AEF significantly enhanced biomass accumulation and root development in oilseed rape. The increased growth-promoting effects of the composite strains were observed to be associated with to their phosphate-solubilizing capacities. Both scales confirmed that compared to single inoculation, composite inoculation of PSB is more beneficial for plant growth. This study provides composite inoculation materials and foundational data to support the bioremediation of P imbalance in soil.

Insight into the mechanisms of plant growth promoting strain ZY2 in improving phytoremediation efficiency in perfluorooctanoic acid (PFOA)-contaminated soil

Perfluorooctanoic acid (PFOA) is an anthropogenic perfluorinated alkyl substance which can enter the food chain and pose health risks. The hydrophilic carboxyl head of PFOA enhances its solubility in water, making it easier for PFOA to migrate with soil water and be absorbed by plants from the soil. Plant growth promoting bacteria (PGPR) have the ability to compensate for plant growth disadvantage under unfavorable conditions and are therefore likely to reduce the negative effects of PFOA phytotoxicity on plant growth. However, the effectiveness of the PGPR-assisted plant systems for remediation of PFOA-contaminated soil has not yet been demonstrated. To this end, a novel strain of Rhizobium sp. was isolated and named as ZY2, which is tolerant to PFOA and exhibits significant plant growth-promoting trains. The results indicated that inoculation with strain ZY2 significantly increased the biomass of oilseed rape. Notably, the accumulation content of PFOA in oilseed rape roots increased significantly by 89.0 % and the removal of PFOA from the soil increased over 3 times after inoculation with ZY2. In addition, inoculated ZY2 also altered the rhizosphere soil bacterial community structure which might correlate with the production of a series of hydrolases and reductases involved in soil carbon and nitrogen cycling processes. Generally, this study offered a novel approach for establishing an effective phytoremediation system in PFOA-contaminated soil.

Synergistic effects of rhizosphere effect and combined organic and chemical fertilizers application on soil bacterial diversity and community structure in oilseed rape cultivation.

The combined application of chemical and organic fertilizers has been recognized to enhance soil fertility and foster the soil microbial ecosystem. However, the optimal ratio of chemical and organic fertilizers in oilseed rape cultivation is still uncertain, and the role of rhizosphere effect is still unclear. Thus, this study aimed to elucidate the impacts of varying ratios of chemical and organic fertilizers on the structure and potential functionalities of rhizosphere and non-rhizosphere soil microbial communities. The interplay of microbial communities with soil properties and oilseed rape root exudates was investigated in controlled pot cultivations receiving varying ratios of chemical and organic fertilizers. Results indicated clear segregation in the soil bacterial community, influenced by both fertilization treatments and rhizosphere effects. The bacterial community structure significantly correlated with nitrate nitrogen, organic acids, and dissolved organic carbon (DOC) content. Rhizosphere effects led to increased bacteria abundance, reduced diversity, and decreased network stability. Notably, F3 treatment receiving 25% chemical and 75% organic fertilizers showed a significantly higher abundance at 1.43 × 1011 copies g-1 dry soil, accompanied by increased species and genetic diversity, and ecological network complexity. This treatment also yielded the highest aboveground biomass of oilseed rape. However, the application of organic fertilizers also increased the risk of plant pathogenicity. This study reveals the impact of fertilizers and rhizosphere effects on soil microbial community structure and function, shedding light on the establishment of more effective fertilization schemes for oilseed rape agriculture.

Silicon improves root functioning and water management as well as alleviates oxidative stress in oilseed rape under drought conditions.

The aim of our study was to examine how silicon regulates water uptake by oilseed rape roots under drought conditions and which components of the antioxidant system take part in alleviating stress-induced ROS generation in the roots. The study analyzed mainly the changes in the roots and also some changes in the leaves of oilseed rape plants, including total silicon content, relative water content, osmotic potential, stomatal conductance, abscisic acid level, the accumulation of BnPIP1, BnPIP2-1-7 and BnTIP1 aquaporins, and the activity of antioxidant enzymes. It was shown that plants growing in well-watered conditions and supplemented with silicon accumulate smaller amounts of this element in the roots and also have higher relative water content in the leaves compared to the control plants. It was demonstrated for the first time that BnTIP1 accumulation in oilseed rape roots is reduced under drought compared to wellwatered plants, and that this effect is intensified in plants supplemented with silicon. In addition, it was shown that silicon supplementation of oilseed rape increases catalase activity in the roots, which correlates with their high metabolic activity under drought and ultimately stimulates their growth. It was shown that silicon improves water balance in oilseed rape plants subjected to drought stress, and that an important role in these processes is played by tonoplast aquaporins. In addition, it was demonstrated that silicon reduces oxidative stress in roots under drought conditions by increasing the activity of catalase.

Evidence for the transportation of aggregated microplastics in the symplast pathway of oilseed rape roots and their impact on plant growth

As an emerging contaminant, microplastics are absorbed by crops, causing diverse impacts on plants. Plants may have different physiological responses to different uptake modes of microplastics various stage of growth. In this study, the distribution of polystyrene (PS) microspheres in the roots of oilseed rape and the physiological responses at different growth stages were investigated by confocal laser scanning microscope, scanning electron microscopy, and biochemical analysis. This study, conducted via scanning electron microscopy, discovered that agglomerates of microspheres, rather than individual plastic pellets, were taken up by plant roots in solution for the first time. The agglomerates subsequently migrate into the vascular bundles of the root system. Moreover, this study provided the proof for the first time that PS is transported in plants via the symplast system. On the physiological and biochemical function, the exposure of PS at the flowering and bolting stages caused oxidative stress on oilseed rape. That is, the addition of PS with different particle sizes significantly increased peroxidase (POD), malondialdehyde (MDA), photosynthetic rate, chlorophyll content and inhibited superoxide dismutase (SOD) content in oilseed rape at different developmental stages. These changes regulated the chloroplast structure and chlorophyll synthesis, maintained a high photosynthetic rate, and mitigated the toxicity of PS. In addition, correlation analysis showed that MDA and citric acid contents were significantly positively correlated with chlorophyll contents (p < 0.05), which suggested that the 80 nm PS treatment stimulated organic acid secretion in oilseed rape at the bolting stage to maintain a higher chlorophyll content. This study expands the current understanding of the effects of microplastics on crop growth, and the results holding significant implications for exploring the impact of microplastics on vegetables during various developmental stages and for future risk assessment.

Contrasting interactions of the aggressive Verticillium longisporum lineage A1/D1 and the non‐aggressive A1/D2 lineage with roots of oilseed rape

AbstractVerticillium longisporum is a soilborne fungal vascular pathogen of Brassica crops. Three hybrid lineages originating from three independent hybridization events of four haploid Verticillium parents are known. V. longisporum lineage A1/D2 has only been found in horseradish and previous pathogenicity tests have shown that it is non‐aggressive on oilseed rape (Brassica napus). The aim of this study was to investigate the interaction of the non‐aggressive lineage A1/D2 with oilseed rape in comparison with the aggressive A1/D1 lineage. Although A1/D2 did not cause severe disease symptoms, the study revealed restricted root infection and systemic colonization by this lineage, as assessed by quantitative PCR of fungal DNA. Assessment of root surface colonization by confocal laser microscopy indicated early sporulation, disorganized loosely attached hyphal growth and hyphal coiling of A1/D2. By contrast, A1/D1 showed organized hyphal growth tight to the root surface, as well as hyphal swellings at points of penetration. Vascular colonization was studied with transmission electron microscopy, which revealed less vessel colonization, higher intensity of vascular responses and lower plant cell wall degradation in A1/D2‐treated plants in comparison with A1/D1. Vascular responses consisted of strong coating of vessel walls and fungal hyphae with an electron‐dense material, indicating higher intensity of plant defence in comparison with A1/D1. The results, for the first time, demonstrate stem colonization and thus a basic level of pathogenic interaction of non‐aggressive strains of A1/D2 with oilseed rape associated with a lack of severe disease symptoms, which indicate tolerance in oilseed rape to lineage A1/D2.

Detection of lead content in oilseed rape leaves and roots based on deep transfer learning and hyperspectral imaging technology

The evaluation capability of hyperspectral imaging technology was studied for the forecasts of heavy metal lead concentration of oilseed rape plant. In addition, a transfer stacked auto-encoder (T-SAE) algorithm including two network methods, the dual-model T-SAE and the single-model T-SAE, was proposed in this paper. The hyperspectral images of oilseed rape leaf and root were acquired under different Pb stress concentrations. The entire region of the oilseed rape leaf (or root) was selected as the region of interest (ROI) to extract the spectral data, and standard normalized variable (SNV), first derivative (1st Der) and second derivative (2nd Der) were used to preprocess the ROI spectra. Besides, the principal component analysis (PCA) algorithm was used to reduce the dimensionality of the spectral data before and after preprocessing. Hence, the best pre-processed data was determined for subsequent research and analysis. Furthermore, the SAE deep learning networks were built based on the oilseed rape leaf data, oilseed rape root data, and the combined data of oilseed rape leaf and root based on the best pre-processed spectral data. Finally, the T-SAE models were obtained through transfer learning of the best SAE deep learning network. The results show that the best preprocessing algorithms of the oilseed rape leaf and root spectra were SNV and 1st Der algorithm, respectively. In addition, the prediction set recognition accuracy of the best T-SAE model of Pb stress gradient in oilseed rape plants was 98.75%. Additionally, the prediction set coefficient of determination of the best T-SAE model of the Pb content in the oilseed rape leaf and root data were 0.9215 and 0.9349, respectively. Therefore, a deep transfer learning method combined with hyperspectral imaging technology can effectively realize the the qualitative and quantitative detection of heavy metal Pb in oilseed rape plants.

Arabidopsis Growth-Promotion and Root Architecture Responses to the Beneficial Rhizobacterium Phyllobacterium brassicacearum Strain STM196 Are Independent of the Nitrate Assimilatory Pathway.

Phyllobacterium brassicacearum STM196, a plant growth-promoting rhizobacterium isolated from roots of oilseed rape, stimulates Arabidopsis growth. We have previously shown that the NRT2.5 and NRT2.6 genes are required for this growth promotion response. Since these genes are members of the NRT2 family of nitrate transporters, the nitrogen assimilatory pathway could be involved in growth promotion by STM196. We address this hypothesis using two nitrate reductase mutants, G5 deleted in the major nitrate reductase gene NIA2 and G′4-3 altered in both NIA1 and NIA2 genes. Both mutants had a reduced growth rate and STM196 failed to increase their biomass production on a medium containing NO3− as the sole nitrogen source. However, they both displayed similar growth promotion by STM196 when grown on an NH4+ medium. STM196 was able to stimulate lateral roots development of the mutants under both nutrition conditions. Altogether, our results indicate that the nitrate assimilatory metabolism is not a primary target of STM196 interaction and is not involved in the root developmental response. The NIA1 transcript level was reduced in the shoots of nrt2.5 and nrt2.6 mutants suggesting a role for this nitrate reductase isoform independently from its role in nitrate assimilation.

Development of a Species-Specific SCAR-PCR Assay for Direct Detection of Sugar Beet Cyst Nematode (Heterodera schachtii) from Infected Roots and Soil Samples.

Sugar beet cyst nematode (SBCN, Heterodera schachtii) is an important nematode that causes significant yield losses of 25–50% or more in most areas of sugar beet production worldwide. Rapid and accurate identification of this species is essential to support decisions on pest management. However, the difference between H. schachtii and other Heterodera spp. based on morphology is a challenging task. In the present study, a SCAR-PCR assay was developed to identify and differentiate H. schachtii in infected root and soil samples. H. schachtii-species-specific SCAR-PCR primers OPA06-HsF and OPA06-HsR were designed from the randomly amplified polymorphic DNA (RAPD) marker amplified with random primer OPA06. The developed primers specifically amplify a 922-bp fragment from the target populations but did not amplify DNA from non-target cyst nematodes including Heterodera, Globodera, Cactodera, and other related species tested in this study. The sensitivity detection indicated that 5 × 10−4 of a single cyst, 1/320 of a single second-stage juvenile (J2), or 10 pg of genomic DNA could be detected. The assay accurately identifies the different stages of H. schachtii in sugar beet and oilseed rape roots as well as a single J2 in 10 g of soil. Finally, the SCAR-PCR assay detected H. schachtii in seven samples out of the fifteen field samples. The assay will not only be useful for differentiating H. schachtii from mixed populations of Heterodera spp. but also for effective detection of the species directly from infested samples. The assay also requires no expertise in the taxonomy and morphology of the species but serves to improve the diagnosis of H. schachtii in infested fields.

Response of winter oilseed rape to differentiated foliar fertilisation

This article presents results of a three-year field experiment laid out on medium textured soil, in north-eastern Poland. Winter oilseed rape was sprayed with foliar fertilisers AgravitaActive 48 (AA48) - NPK 8:8.7:16.6 and AgravitaActive70 (AA70) - NPK 10:22.7:6.6 at different phases of the crop’s vegetative growth (BBCH 14, BBCH 35). The impact of the fertilisers on the yield of seeds, straw, total protein, crude fat, and on the content of macro- and micronutrients in aerial parts (BBCH 20 and 89) and roots (BBCH 20) of oilseed rape was evaluated. Foliar nutrition of oilseed rape plants with AA48 and AA70 significantly increased the seed yield of oilseed rape. The best yield-stimulating effect was achieved after the application of AA48 in autumn. Fertilisation of oilseed rape in that season of the year caused an increase in seed yield by 430 kg ha-1. Each fertiliser contributed to a rise in the yield of protein and yield of crude fat but had no effect on the content of magnesium, copper, and zinc in seeds.

Waitea circinata var. zeae Causing Root Rot of Cabbage and Oilseed Rape.

Cabbage, a widely used and popular vegetable, and oilseed rape, the second most valuable oilseed crop in the world, are two important species from the Brassicaceae family. Two geographically separated outbreaks of cabbage and oilseed rape root rot with estimated incidence of 15 and 20%, respectively, were recorded during 2017 in the Vojvodina region, Serbia. Twelve hyphal-tip isolates were obtained from symptomatic cabbage and oilseed rape plants and identified as Waitea circinata var. zeae based on morphological and molecular features. This indicates that W. circinata var. zeae has expanded its host range to the Brassicaceae family. Sequence analyses of internal transcribed spacer (ITS) and large subunit of the ribosomal DNA, RPB2, and β-tubulin genes revealed the highest similarity with multiple W. circinata var. zeae. Neighbor-joining analyses of ITS sequences resulted in a phylogenetic tree with one well-defined branch of W. circinata var. zeae, with two separate groups. All Serbian isolates and the majority of isolates originating from natural infection of dicotyledonous plants grouped together in group I. Following artificial inoculation, W. circinata var. zeae isolates caused mild to medium root necrosis of seedlings of 2 monocotyledonous and 12 dicotyledonous plant species, implying a wider host range than was known for W. circinata var. zeae. Additionally, this is the first occurrence of W. circinata var. zeae on dicotyledonous host plants in Europe. Because cabbage and oilseed rape are important crops grown worldwide, the occurrence of this new soilborne pathogen with a broad host range imposes the necessity for changes in routine disease control practices, particularly crop rotation.

Root Distribution of Brassica napus and Vicia faba within the Sheath of Root or Earthworm Biopore

Root growth through biopores is facilitated by low mechanical impedance and nutrient enrichment due to the deposition of organic material at the biopore sheath. Plant roots and earthworms impact biopore sheath properties differently. However, the literature lacks a quantitative study of the root distribution within the sheath of pores, which were originated by taproots or earthworms. According to previous literature on pore connectivity, it can be hypothesized that precrops encourage root growth into the biopore sheath in comparison to an earthworm characterized sheath. A pot experiment was performed to compare the root distribution of spring oilseed rape (Brassica napus L.) and faba bean (Vicia faba L.) within the biopore sheath of two different biopore types. The biopore sheath was characterized by taprooted chicory (Cichorium intybus L.) or anecic earthworm (Lumbricus terrestris L.). Roots were sampled at the biopore lumen and at lateral distances of 0–2, 2–4, 4–8 (sheath) and 20–36 mm (bulk soil) from the biopore wall surface. In both pore types &gt;50% of the root length (cm) and &gt;70% fine roots of oilseed rape were found in a comparatively small soil area (Lumen + 2 mm). On the contrary, faba bean grew primarily through the bulk soil with &gt;75% root length and rarely into the biopore sheath in both pore types. In both species there was a lateral decrease of the total nitrogen (Nt)-content from biopore wall (Mean ± SE: 0.061% ± 0.002%) to bulk soil (0.053% ± 0.002%), but no significant difference between the pore types. The results of the current study illustrate that the root growth of spring oilseed rape and faba bean was not encouraged by the precrop in comparison to the earthworm characterized sheath.

Reclassification of the biocontrol agents Bacillus subtilis BY-2 and Tu-100 as Bacillus velezensis and insights into the genomic and specialized metabolite diversity of the species.

The genomes of two historical Bacillus species strains isolated from the roots of oilseed rape and used routinely in PR China as biocontrol agents to suppress Sclerotinia disease were sequenced. Average nucleotide identity (ANI) and digital DNA–DNA hybridization analyses demonstrated that they were originally misclassified as Bacillus subtilis and now belong to the bacterial species Bacillus velezensis . A broader ANI analysis of available Bacillus genomes identified 292 B. velezensis genomes that were then subjected to core gene analysis and phylogenomics. Prediction and dereplication of specialized metabolite biosynthetic gene clusters (BGCs) defined the prevalence of multiple antimicrobial-associated BGCs and highlighted the natural product potential of B. velezensis . By defining the core and accessory antimicrobial biosynthetic capacity of the species, we offer an in-depth understanding of B. velezensis natural product capacity to facilitate the selection and testing of B. velezensis strains for use as biological control agents.

Selenium activates components of iron acquisition machinery in oilseed rape roots

Beneficial elements may stimulate plant growth by favoring the availability of essential nutrients for metabolic processes. This study addresses the still unexplored question whether the beneficial action of selenium (Se) on plants can be due to its interaction with iron (Fe). Oilseed rape (Brassica napus) plants were grown hydroponically without (–Se) or with 10 μM Na2SeO4 (+Se) and exposed to either Fe adequate (+Fe) or starvation (–Fe) treatments. Selenium enhanced leaf chlorophyll concentration, photochemical parameters and CO2 fixation. Although Se did not significantly increase total leaf Fe concentration, the concentration of cytoplasmic FeII pool was enhanced under –Fe + Se conditions. However, the most conspicuous Se effects occurred in Fe-deficient roots. Selenium upregulated both the root expression levels of genes encoding FERRIC-REDUCTION OXIDASE (FRO1) and the activity of FRO and exacerbated the stimulatory effect of –Fe on the exudation rate of organic acids and phenolic compounds. Both –Se and + Se plants used FeIIIEDTA in similar way, while only +Se plants were able to take advantage of the sparingly soluble Fe(OH)3. In order to explore the mechanism of Se action, we recorded higher endogenous level of NO and upregulation of ETHYLENE RESPONSE FACTOR 2 (ERF2) by Se irrespective of Fe conditions. Our results show that Se augments root machinery for Fe acquisition mainly through activation of Fe signaling components.

Suppression of abscisic acid biosynthesis at the early infection stage of Verticillium longisporum in oilseed rape (Brassica napus).

Summary Verticillium longisporum infects oilseed rape (Brassica napus) and Arabidopsis thaliana. To investigate the early response of oilseed rape to the fungal infection, we determined transcriptomic changes in oilseed rape roots at 6 days post‐inoculation (dpi) by RNA‐Seq analysis, in which non‐infected roots served as a control. Strikingly, a subset of genes involved in abscisic acid (ABA) biosynthesis was found to be down‐regulated and the ABA level was accordingly attenuated in 6 dpi oilseed rape as compared with the control. Gene expression analysis revealed that this was mainly attributed to the suppression of BnNCED3‐mediated ABA biosynthesis, involving, for example, BnWRKY57. However, this down‐regulation of ABA biosynthesis could not be observed in infected Arabidopsis roots. Arabidopsis ABA‐ defective mutants nced3 and aao3 displayed pronounced tolerance to the fungal infection with delayed and impeded symptom development, even though fungal colonization was not affected in both mutants. These data suggest that ABA appears to be required for full susceptibility of Arabidopsis to the fungal infection. Furthermore, we found that in both 6 dpi oilseed rape and the Arabidopsis nced3 mutant, the salicylic acid (SA) signalling pathway was induced while the jasmonic acid (JA)/ethylene (ET) signalling pathway was concomitantly mitigated. Following these data, we conclude that in oilseed rape the V. longisporum infection triggers a host‐specific suppression of the NCED3‐mediated ABA biosynthesis, consequently increasing plant tolerance to the fungal infection. We believe that this might be part of the virulence strategy of V. longisporum to initiate/establish a long‐lasting compatible interaction with oilseed rape (coexistence), which appears to be different from the infection process in Arabidopsis.

Comparing Macropore Exploration by Faba Bean, Wheat, Barley and Oilseed Rape Roots Using In Situ Endoscopy

Large-sized biopores in the subsoil can provide rapid access to deeper soil layers and potentially enhance nutrient acquisition. Besides site conditions, the extent of these effects depends on crop root architecture. The aim of this study was to compare barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), oilseed rape (Brassica napus L.) and faba bean (Vicia faba L.) with respect to time of macropore entry, root soil contact and root hair formation. Crops were grown in columns with condensed subsoil and an artificial macropore. Root growth dynamics in the macropore were monitored with in situ endoscopy. After harvest, the share of roots in macropores was quantified. Oilseed rape had many vertical roots with root hairs contacting the pore wall and was the only crop with preferential root growth in macropores. Cereal roots were mostly crossing the pore horizontally, partially with root hairs and partially contacting the pore wall. Nearly all faba bean roots were crossing the pore without root-soil contact. Our results support the notion that the importance of biopores for crop root growth and resource acquisition depends on root architecture. Under the conditions of the study with sufficient water supply and therefore comparatively low penetration resistance, macropores were only marginally used by cereals and faba bean. Oilseed rape roots were apparently much more sensitive to mechanical impedance, and the pores were used more intensively.

Electrical impedance tomography as a tool for phenotyping plant roots

BackgroundPlant roots are complex, three-dimensional structures that play a central role in anchorage, water and nutrient acquisition, storage and interaction with rhizosphere microbes. Studying the development of the plant root system architecture is inherently difficult as soil is not a transparent medium.ResultsThis study uses electrical impedance tomography (EIT) to visualise oilseed rape root development in horticultural compost. The development of healthy, control plants and those infected with the gall-forming pathogen, Plasmodiophora brassicae—the causative agent of clubroot disease—were compared. EIT measurements were used to quantify the development of the root system and distinguish between control and infected plants at the onset of gall formation, approximately 20 days after inoculation. Although clear and stark differences between healthy and infected plants were obtained by careful (and hence laborious) packing of the growth medium in layers within the pots; clubroot identification is still possible without a laborious vessel filling protocol.ConclusionsThese results demonstrate the utility of EIT as a low-cost, non-invasive, non-destructive method for characterising root system architecture and plant-pathogen interactions in opaque growth media. As such it offers advantages over other root characterisation techniques and has the potential to act as a low-cost tool for plant phenotyping.

The impact of non-chemical weed control methods and biopreparations on winter oilseed rape preparation for over-wintering and productivity

The current study was aimed to establish the impact of non-chemical weed control methods (thermal, mechanical andsmothering) and biopreparations on winter oilseed rape (Brassica napus L.) preparation for over-wintering and productivity under the conditions of the organic farming system. During the 2014–2016 period, a field experiment was conducted at the Experimental Station of Aleksandras Stulginskis University on Calc(ar)i-Endohypogleyic Luvisol (LVg-n-w-cc). The field experiment treatments were the following: Factor A – non-chemical weed control methods: 1) thermal (water steam), 2) mechanical (inter-row loosening), 3) smothering (self-regulation, sowing with narrow inter-rows); Factor B – application of biopreparations: 1) without application, 2) with application. During the period of autumn vegetation, in the smothering method plots, where the winter oilseed rape crop density was 1.5–2.4 times lower than that in the plots of thermal and mechanical weed control methods, the significantly highest aboveground mass of plant, number of leaves per plant, diameter of root collar, root area, total root length, root biomass of plant and leaf area of plant were determined, and in 2015 the highest chlorophyll index was measured in the leaves. In 2014 the application of biopreprations in the smothering method plots significantly increased the aboveground mass of plant (41.3%), the total root length (33.2%) and the root biomass of plant (28.0%). In 2004 the diameter of winter oilseed rape root collar depended on the leaf area of plant (r = 0.83, P &lt; 0.05) and the root area of plant (r = 0.86, P &lt; 0.05), and in 2015 it depended on the leaf area of plant (r = 0.89, P &lt; 0.05), the root area (r = 0.99, P &lt; 0.01), the total root length (r = 0.98, P &lt; 0.01) and the root biomass of plant (r = 0.99, P &lt; 0.01). Positive, strong and very strong, and statistically significant relationships were established between the leaf area of oilseed rape and the root area, the total root length and the root biomass of plant. In the spring of 2015, during the renewed oilseed rape vegetation stage, the highest crop density (98.0 units m–2) and over-wintering (96.0%) were obtained in the plots of the mechanical weed control method in combination with biopreparations. In the spring of 2016, different nonchemical weed control methods and biopreparations did not have any significant effect on the oilseed rape over-wintering and the crop density. In 2015, different non-chemical weed control methods did not have any significant influence on oilseed rape biometric parameters before harvesting. In 2016, in the smothering method plots a significantly lower mass of oilseed rape and the number of branches per plant were formed compared to those of other used treatments. The highest number of pods per plant was determined in the smothering method plots in combination with biopreparations. In 2015 biopreprations in the smothering method plots significantly increased the 1 000 seed mass, and in 2016 they increased the number of pods per plant, respectively 7.2 and 35.6%. In the droughty year of 2015, the significantly highest winter oilseed rape seed yield was recorded in the plots of the mechanical weed control method, and in the moist year of 2016, the highest yield was in the smothering method plots with biopreparations. In 2015 biopreprations significantly increased the oilseed rape seed yield in the plots of thermal and mechanical weed control methods, and in 2016 they increased the yield in the smothering method plots, respectively 43.4, 25.1 and 51.5%. In 2015 the winter oilseed rape seed yield depended on the crop density (r = 0.86, P &lt; 0.05) and the plant height (r = 0.94, P &lt; 0.01), and in 2016 it depended on the number of pods per plant (r = 0.98, P &lt; 0.01) and the plant height (r = 0.85, P &lt; 0.05).

Methyl jasmonate alleviates arsenic-induced oxidative damage and modulates the ascorbate–glutathione cycle in oilseed rape roots

Methyl jasmonate (MJ) is an important plant growth regulator, involves in various physiological processes of plants. In the present study, role of MJ in tolerance to oilseed rape (Brassica napus L.) roots under arsenic (As) stress was investigated. The treatments were comprised of three MJ doses (0, 0.1, and 1 µM) and two levels of As (0 and 200 µM). Arsenic stress resulted in oxidative damage as evidenced by decreased root growth and enhanced reactive oxygen species and lipid peroxidation. However, plants treated with MJ decreased the H2O2 and O2 ·− contents in roots and have higher antioxidant activities. Importantly, results showed that MJ enhanced the redox states of AsA and GSH, and the related enzymes involved in the AsA–GSH cycle. Moreover, MJ also induced the secondary metabolites related enzymes (PAL and PPO) activities, under As stress. PAL and PPO expression was further increased by MJ application in the roots of B. napus under As stress. MJ also reduced the total As content compared with As alone treated plants. These findings suggest the role of MJ in mitigation of the As-induced oxidative damage by regulating AsA and GSH redox states and by reducing As uptake in both cultivars.

Antioxidant capacity of oilseed rape (Brassica napus) in different soil types

This work considers the results obtained by testing the parameters of antioxidant status in leaves and roots of oilseed rape at different growth stages (phase I: formation of leaf rosettes and preparing for winter hibernation; phase II: after the winter hibernation; phase III: flowering) grown in semicontrolled field conditions on different soil types. The experiment was conducted on four oilseed rape genotypes (Banacanka, Jasna, Kata, and Zlatna) in semicontrolled conditions in containers with three soil types: chernozem, solonetz, and solonchak. The germination failed on solonchak due to the excessive amount of salt, but results were obtained for plant material on chernozem and solonetz. The following parameters were examined: superoxide dismutase (SOD) enzyme activity, glutathione peroxidase (GPx) activity, lipid peroxidation (LP) intensity, glutathione (GSH) content, and total antioxidant capacity (by ferric reducing antioxidant power, FRAP method). The activity of all the tested parameters of antioxidant status in all genotypes, both in leaves and roots, was higher in plants grown on solonetz soil compared to plants grown on chernozem. Furthermore, the activity of all the tested parameters on both soil types was highest in the second phase of testing, the stage after the winter hibernation, because the plants were exposed to low temperatures in addition to salt stress. The vital thing to note is that GPx activity is important for the defense at the initial stages of growth, while in the later growth stages SOD assumes this role. The genotype Banacanka has been distinguished as the most tolerant, while the genotype Zlatna was the most sensitive.