Oilseed Rape Plants Research Articles

Enhanced root system architecture in oilseed rape transformed with Rhizobium rhizogenes

Transformation of plants using wild strains of agrobacteria is termed natural transformation and is not covered by GMO legislation in e.g. European Union and Japan. In the current study, offspring lines (A11 and B3) of Rhizobium rhizogenes naturally transformed oilseed rape (Brassica napus) were randomly selected to characterize the morphological traits, and analyze the implications of such morphological changes on plant drought resilience. It was found that the introduction of Ri-genes altered the biomass partitioning to above- and under-ground parts of oilseed rape plants. Compared to the wild type (WT), the A11 and B3 lines exhibited 1.2–4.0 folds lower leaf and stem dry weight, leaf area and plant height, but had 1.3–5.8 folds greater root dry weight, root length and root surface area, resulting in a significantly enhanced root: shoot dry mass ratio and root surface area: leaf area ratio. In addition, the introduction of Ri-genes conferred reduced stomatal pore aperture and increased stomatal density in the B3 line, and increased leaf thickness in A11 line, which could benefit plant drought resilience. Finally, the modulations in morphological traits as a consequence of transformation with Ri-genes are discussed concerning resilience in water-limited conditions. These findings reveal the potential of natural transformation with R. rhizogenes for drought-targeted breeding in crops.

Determinants of oilseed rape-service plant intercropping performance variability across a farmers’ fields network in Western Switzerland

The intercropping of winter oilseed rape with frost-sensitive service plants can provide a diversity of services including weed control and N supply for oilseed rape. This practice started to be adopted by farmers and has therefore become one of the most popular intercropping in Western Europe. However, in Switzerland, such intercropping leads to contrasting yields. The growth of service plants and the benefits they provide have also been found to be variable. The factors explaining these variabilities remain unclear. Our study aimed to better understand this variability under a temperate climate thanks to the regional agronomic diagnosis framework. In this study, we first investigated the main factors explaining this variability and then aimed to rank them to identify ways to better manage such intercropping systems. A network of 28 farmers’ fields planted with winter oilseed rape intercropped with service plant mixtures was studied. Farmers’ practices were diverse in terms of specific composition of the service plant mixture, pest management, and fertilization. We observed that the growth of oilseed rape and service plants in fall was highly variable. We determined that in late fall, the main drivers of the service plant mixture dry weight were specific composition of the mixture and precipitation. The introduction of buckwheat in the service plant mixture enhanced its late fall biomass. The oilseed rape grain yields ranged from 0.4 to 5.0 t ha−1 and were lower than that of the local reference in 75% of the fields. This was mainly explained by insect pest damage in spring due to a very limited use of insecticide in our field network combined with a lack of alternative pest management strategies. This work provides further elements to investigate the causes leading to the high variability we observed, together with the local observations that will benefit the farmers.

Estimation of flea beetle damage in the field using a multistage deep learning-based solution

Estimation of damage in plants is a key issue for crop protection. Currently, experts in the field manually assess the plots. This is a time-consuming task that can be automated thanks to the latest technology in computer vision (CV). The use of image-based systems and recently deep learning-based systems have provided good results in several agricultural applications. These image-based applications outperform expert evaluation in controlled environments, and now they are being progressively included in non-controlled field applications.A novel solution based on deep learning techniques in combination with image processing methods is proposed to tackle the estimate of plant damage in the field. The proposed solution is a two-stage algorithm. In a first stage, the single plants in the plots are detected by an object detection YOLO based model. Then a regression model is applied to estimate the damage of each individual plant. The solution has been developed and validated in oilseed rape plants to estimate the damage caused by flea beetle.The crop detection model achieves a mean precision average of 91% with a mAP@0.50 of 0.99 and a mAP@0.95 of 0.91 for oilseed rape specifically. The regression model to estimate up to 60% of damage degree in single plants achieves a MAE of 7.11, and R2 of 0.46 in comparison with manual evaluations done plant by plant by experts. Models are deployed in a docker, and with a REST API communication protocol they can be inferred directly for images acquired in the field from a mobile device.

Plants interfere with non-self recognition of a phytopathogenic fungus via proline accumulation to facilitate mycovirus transmission

Non-self recognition is a fundamental aspect of life, serving as a crucial mechanism for mitigating proliferation of molecular parasites within fungal populations. However, studies investigating the potential interference of plants with fungal non-self recognition mechanisms are limited. Here, we demonstrate a pronounced increase in the efficiency of horizontal mycovirus transmission between vegetatively incompatible Sclerotinia sclerotiorum strains in planta as compared to in vitro. This increased efficiency is associated with elevated proline concentration in plants following S. sclerotiorum infection. This surge in proline levels attenuates the non-self recognition reaction among fungi by inhibition of cell death, thereby facilitating mycovirus transmission. Furthermore, our field experiments reveal that the combined deployment of hypovirulent S. sclerotiorum strains harboring hypovirulence-associated mycoviruses (HAVs) together with exogenous proline confers substantial protection to oilseed rape plants against virulent S. sclerotiorum. This unprecedented discovery illuminates a novel pathway by which plants can counteract S. sclerotiorum infection, leveraging the weakening of fungal non-self recognition and promotion of HAVs spread. These promising insights provide an avenue to explore for developing innovative biological control strategies aimed at mitigating fungal diseases in plants by enhancing the efficacy of horizontal HAV transmission.

Behavior of Thiamethoxam and Clothianidin in Young Oilseed Rape Plants before Flowering, Monitored by QuEChERS/LC–MS/MS Protocol

Behavior of Thiamethoxam and Clothianidin in Young Oilseed Rape Plants before Flowering, Monitored by QuEChERS/LC–MS/MS Protocol

A Novel Strain of Bacillus cereus with a Strong Antagonistic Effect Specific to Sclerotinia and Its Genomic and Transcriptomic Analysis.

Sclerotinia, which is caused by Sclerotinia sclerotiorum, is a severe disease of oilseed rape, which is an important oil crop worldwide. In this study, we isolated a novel strain of Bacillus cereus, named B. cereus HF10, from the rhizosphere soil of the reed on the seaside of Yagzhou Bay, Sanya city, Hainan Province, China. HF10 exhibited a significant antagonistic effect on Sclerotinia sclerotiorum, with an inhibition rate of 79%, and to other species in Sclerotinia, but no antagonistic effect was found on various other fungi or bacteria. HF10 had an 82.3% inhibitory effect on the S. sclerotiorum infection of oilseed rape leaves and a 71.7% control effect on Sclerotinia infection in oilseed rape based on in vitro and in vivo experiments, respectively. The genomics and transcriptomics of HF10 and its loss of the antifungal function mutant Y11 were analyzed, and the results provided insight into potential antifungal substances. Our work provides a novel strain, HF10, for developing a promising biological control agent against Sclerotinia, which infects oilseed rape and other plants.

Aphids May Facilitate the Spread of Sclerotinia Stem Rot in Oilseed Rape by Carrying and Depositing Ascospores.

Aphids and Sclerotinia stem rot in oilseed rape are often studied in isolation, and their relationship is rarely explored. Our field studies have revealed a significant positive correlation between the number of aphids and the incidence of Sclerotinia stem rot. Hence, starting with the colonizing stages of the two pests, Breveroryne brassicae was assessed for its potential to acquire, transmit, and inoculate Sclerotinia sclerotiorum by being sprayed with an ascospore suspension. Moreover, distinctions in aphid feeding behavior were examined between aphids on inoculated/uninoculated winter and spring oilseed rape plants or aphids, both with and without S. sclerotiorum ascospores, using electropenetrography (EPG). The results showed that aphid feeding followed by dropping ascospore suspension significantly increased the incidence of S. sclerotiorum. Ascospores were able to adhere to aphids and were carried by aphids to healthy plants, causing disease. The results of the EPG analysis indicated that aphid feeding behavior was significantly altered in all leaf tissue levels following infection with S. sclerotiorum. Specifically, aphids initiated their first puncture significantly sooner, began probing mesophyll cells earlier, had a significantly shorter pathway duration, and secreted saliva more frequently but reduced salivation prior to feeding and ingestion compared to aphids feeding on uninfected oilseed rape. Additionally, the feeding behavior of aphids carrying ascospores was markedly different from that of aphids not carrying ascospores, implying that ascospores directly influence aphid feeding behavior but that this influence appeared to be beneficial only for S. sclerotiorum infection. Aphids carrying ascospores started to puncture cells more quickly, with a significant increase in the frequency and duration of short probes and cell punctures, shortened pathway durations, and reduced salivation before feeding compared to aphids not carrying ascospores. It is clear that there is an interaction between aphids and S. sclerotiorum. The impact of S. sclerotiorum on aphid feeding behavior is directional, favoring the spread of the fungus.

Genetic Variation of Turnip Yellows Virus in Arable and Vegetable Brassica Crops, Perennial Wild Brassicas, and Aphid Vectors Collected from the Plants.

Turnip yellows virus (TuYV; Polerovirus, Solemoviridae) infects and causes yield losses in a range of economically important crop species, particularly the Brassicaceae. It is persistently transmitted by several aphid species and is difficult to control. Although the incidence and genetic diversity of TuYV has been extensively investigated in recent years, little is known about how the diversity within host plants relates to that in its vectors. Arable oilseed rape (Brassica napus) and vegetable brassica plants (Brassica oleracea), wild cabbage (B. oleracea), and aphids present on these plants were sampled in the field in three regions of the United Kingdom. High levels of TuYV (82 to 97%) were detected in plants in all three regions following enzyme-linked immunosorbent assays. TuYV was detected by reverse transcription polymerase chain reaction in Brevicoryne brassicae aphids collected from plants, and TuYV sequences were obtained. Two TuYV open reading frames, ORF0 and ORF3, were partially sequenced from 15 plants, and from one aphid collected from each plant. Comparative analyses between TuYV sequences from host plants and B. brassicae collected from respective plants revealed differences between some ORF0 sequences, which possibly indicated that at least two of the aphids might not have been carrying the same TuYV isolates as those present in their host plants. Maximum likelihood phylogenetic analyses including published, the new TuYV sequences described above, 101 previously unpublished sequences of TuYV from oilseed rape in the United Kingdom, and 13 also previously unpublished sequences of TuYV from oilseed rape in Europe and China revealed three distinct major clades for ORF0 and one for ORF3, with some distinct subclades. Some clustering was related to geographic origin. Explanations for TuYV sequence differences between plants and the aphids present on respective plants and implications for the epidemiology and control of TuYV are discussed.

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.

Organ-Level Instance Segmentation of Oilseed Rape at Seedling Stage Based on 3D Point Cloud

Highlights Provides a low-cost, fast, accurate, and non-destructive method for segmenting stems and leaves of oilseed rape at the seedling stage. Different varieties and leaf shapes of oilseed rape can all be accurately and efficiently segmented at organ level. The results of accurate organ instance segmentation are used for further organ morphological structure analysis and organ-level phenotype extraction. The calculated phenotypic data is highly correlated with the true phenotypic data. Abstract. Organ-level plant point cloud instance segmentation is crucial for three-dimensional (3D) plant structure investigations and plant phenotypic formations. Due to the complexity of 3D plant structures, accurate plant organ segmentation methods remain a bottleneck in current development of plant organ phenotypes. In this work, we present a fast, accurate, low-cost, and non-destructive method of stem and leaf instance segmentation at the organ level for oilseed rape point cloud. Firstly, we use a 3D scanner to obtain the point cloud of oilseed rape plants. Then, principal component analysis (PCA) is used to perform surface feature extraction on the point cloud after preprocessing. Subsequently, the stems and leaves in different features are segmented by region growing. The irrational segmentation results are finally optimized. Segmentation results of stems and leaves of oilseed rape of different sizes and leaf shapes are evaluated using manually segmented oilseed rape point clouds as a benchmark. The precision, recall, F-score, and average accuracy of the proposed stem and leave segmentation method are 0.983, 0.897, 0.937, and 0.883, respectively. The experimental results suggest that the proposed method can accurately segment an oilseed rape 3D point cloud into instances corresponding to the organs of the plant. Additionally, the separated leaf and stem organs of oilseed rape can be further used for plant structure studies and organ phenotype extraction. The organ phenotypic parameters of oilseed rape are calculated based on the results of stem and leaf instances segmentation. The leaf area, stem length and stem angle of oilseed rape calculated from the point cloud are also compared with the corresponding manual measurements, which are highly correlated with coefficients of determination R2 (0.82-0.97). In conclusion, the proposed segmentation method can be applied as a fundamental segmentation step to extract organ phenotype data from oilseed rape plants. Namely, our research is valuable for precision breeding and basic plant research. Keywords: 3D point cloud, Oilseed rape plant, Phenotypic traits, Stem-leaf segmentation.

Effective strategies for reclamation of saline-alkali soil and response mechanisms of the soil-plant system

The combination of amendments has emerged as a potential strategy to efficiently alleviate salt stress in saline-alkali soil. However, knowledge regarding how to optimize the proportion of different amendment materials, comprehensively assess the contribution of each component, and clarify the response mechanisms of the amendment-saline-alkali soil-plant system is incomplete. Based on this, we conducted a pot experiment to evaluate the improvement effect of the combined application of different amendment materials at varying levels and the contribution of the amendment components to alleviating salt stress. Overall, T6 exhibited the most significant improvement effect on the physicochemical and biological properties of the saline-alkali soil and promoted the growth of oilseed rape, with the levels of 2.0 % phosphogypsum, 2.0 % humic acid, 0.25 % bentonite, and 0.03 % sodium carboxymethyl cellulose. Compared with the control group, the EC decreased by 1.51 % to 33.49 %, the soil salt content dropped by 11.40 % to 35.46 %, and the soil soluble Na + concentration significantly declined by 39.47 % to 63.20 %. Additionally, the soil nutrient content and soil microbial community structure were enhanced in treatment groups. Meanwhile, amendments alleviated salt stress in the oilseed rape plant by activating anti-oxidative enzymes and osmoregulatory substances such as soluble sugar and proline, thus improving their ability to remove reactive oxygen species (ROS). The anti-oxidative enzymes such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were significantly increased, with an increase of 10.68 % (SOD, T2) ∼207.31 % (CAT, T6) compared to the control group. The structural equation modeling (SEM) analysis and simulation experiments indicated that the amendment components synergically promoted the amelioration effect on salt stress, and effectively improved soil properties, which affected the response of oilseed rape to soil environment. This research paper provides the relevant reference for the combined application of different amendment materials for soil reclamation.

A causal inference and Bayesian optimisation framework for modelling multi-trait relationships-Proof-of-concept using Brassica napus seed yield under controlled conditions.

The improvement of crop yield is a major breeding target and there is a long history of research that has focussed on unravelling the mechanisms and processes that contribute to yield. Quantitative prediction of the interplay between morphological traits, and the effects of these trait-trait relationships on seed production remains, however, a challenge. Consequently, the extent to which crop varieties optimise their morphology for a given environment is largely unknown. This work presents a new combination of existing methodologies by framing crop breeding as an optimisation problem and evaluates the extent to which existing varieties exhibit optimal morphologies under the test conditions. In this proof-of-concept study using spring and winter oilseed rape plants grown under greenhouse conditions, we employ causal inference to model the hierarchically structured effects of 27 morphological yield traits on each other. We perform Bayesian optimisation of seed yield, to identify and quantify the morphologies of ideotype plants, which are expected to be higher yielding than the varieties in the studied panels. Under the tested growth conditions, we find that existing spring varieties occupy the optimal regions of trait-space, but that potentially high yielding strategies are unexplored in extant winter varieties. The same approach can be used to evaluate trait (morphology) space for any environment.

Local Competition and Enhanced Defense: How Metarhizium brunneum Inhibits Verticillium longisporum in Oilseed Rape Plants.

Metarhizium brunneum is a soil-borne fungal entomopathogen that can be associated with plant roots. Previous studies have demonstrated that root colonization by beneficial fungi can directly affect soil-borne pathogens through competition and antibiosis and can activate a systemic response in plants, resulting in a primed state for a faster and/or stronger response to stressors. However, the mechanisms by which Metarhizium inoculation ameliorates symptoms caused by plant pathogens are not well known. This study evaluated the ability of M. brunneum to protect oilseed rape (Brassica napus L.) plants against the soil-borne pathogen Verticillium longisporum and investigated whether the observed effects are a result of direct interaction and/or plant-mediated effects. In vitro and greenhouse experiments were conducted to measure fungal colonization of the rhizosphere and plant tissues, and targeted gene expression analysis was used to evaluate the plant response. The results show that M. brunneum delayed pathogen colonization of plant root tissues, resulting in decreased disease symptoms. Direct competition and antibiosis were found to be part of the mechanisms, as M. brunneum growth was stimulated by the pathogen and inhibited the in vitro growth of V. longisporum. Additionally, M. brunneum changed the plant response to the pathogen by locally activating key defense hormones in the salicylic acid (SA) and abscisic acid (ABA) pathways. Using a split-root setup, it was demonstrated that there is a plant-mediated effect, as improved plant growth and decreased disease symptoms were observed when M. brunneum was in the systemic compartment. Moreover, a stronger systemic induction of the gene PR1 suggested a priming effect, involving the SA pathway. Overall, this study sheds light on the mechanisms underlying the protective effects of M. brunneum against soil-borne pathogens in oilseed rape plants, highlighting the potential of this fungal entomopathogen as a biocontrol agent in sustainable agriculture.

Proline Enhances Resistance and Recovery of Oilseed Rape after a Simulated Prolonged Drought.

This study was carried out to evaluate the effect of exogenous proline on the growth, biochemical responses, and plant recovery of drought-stressed oilseed rape plants after renewed irrigation. The experiment was conducted under controlled laboratory conditions. After 21 days of cultivation, 3-4 leaf stage seedlings were sprayed with proline (1 mM), then subjected to prolonged drought stress for 8 days to achieve a severe water deficit, next, irrigation was resumed and recovery was assessed after 4 days. The results show that exogenous application of proline reduced the drought-induced growth inhibition of seedlings while maintaining relative water content (RWC) and growth parameters closer to those of irrigated plants. Proline had a positive effect on chlorophyll accumulation and membrane permeability while decreasing ethylene, H2O2, and MDA levels. Moreover, after 4 days of recovery, the H2O2 content of the proline-treated plants was significantly lower (2-fold) and the MDA content was close to that of continuously irrigated plants. Thus, all these biochemical reactions influenced plant survival: after drought + proline treatment, the number of surviving plants was two times higher than that of drought-treated plants. The findings show that exogenous proline has antioxidant, osmotic, and growth-promoting properties that improve the drought tolerance of winter oilseed rape plants and is, therefore, beneficial for drought adaptation in oilseed rape.

Companion plants and straw mulch reduce cabbage stem flea beetle (Psylliodes chrysocephala) damage on oilseed rape.

Plant diversification, especially sowing crops with the addition of companion plants has been demonstrated as a suitable practice to increase insect pest control in multiple cropping systems. Since the ban on use of neonicotinoid seed treatments in oilseed rape (OSR), the harvested area has reduced significantly in Europe, mainly because of the damage caused by cabbage stem flea beetle (Psylliodes chrysocephala). Several companion plants such as legumes and other species of Brassicaceae have been reported as potential companions for OSR but robust evaluation of their efficiency to reduce cabbage stem flea beetle damage in replicated trials is lacking. Four field trials were conducted in the UK and Germany to test the effect of different companion plants, or the addition of straw mulch, on cabbage stem flea beetle adult feeding and larval infestation in OSR. We found significant differences in the level of feeding damage between treatments in all experiments. Combinations of OSR with cereal companion plants or with straw mulch showed the strongest reduction in adult feeding damage. A protective effect of legumes was also observed in one trial. Differences in larval infestation were also observed between treatments but were not consistent and might be more related to the OSR plant biomass than to treatments. This study shows that companion planting can protect OSR crops from cabbage stem flea beetle adult feeding damage. We show for the first time that not only legumes, but also cereals and the application of straw mulch can have a strong protective effect on the crop. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

High Sulfur (S) Supplementation Imparts Waterlogging Tolerance to Oilseed rape (Brassica napus L.) Through Upregulating S Metabolism and Antioxidant Pathways

Waterlogging significantly impacts plant growth and development by altering nutrient uptake and antioxidant enzyme functions, resulting in reduced yield. Plants need sulfur (S) to produce reduced glutathione (GSH), a thiol compound that combats abiotic stresses. It is hypothesized that supplying S to high S-demanding oilseed rape plants beyond its growth requirements can reduce the adverse effect of waterlogging stress. Therefore, this study evaluated the comparative effect of different S doses (mg kg− 1 soil), i.e., no-S (S0), low-S (S1, 35), medium-S (S2, 70), and high-S (S3, 140) on growth, yield and antioxidant defense systems of normal growing and waterlogged oilseed rape plants. Waterlogging was imposed at the inflorescence emergence stage for 7 days by retaining a 3-cm layer of water above the soil surface. Waterlogged plants supplemented with high-S showed improved growth and higher yield than those supplemented with lower S levels, and this response was associated with improved activity/contents of antioxidants, including ascorbate (AsA), GSH, ascorbate peroxidase, catalase, glutathione reductase, glutathione peroxidase, glutathione S-transferase, monodehydroascorbate reductase, and dehydroascorbate reductase, with concomitant lowering of hydrogen peroxide, dehydroascorbate and malondialdehyde content. Furthermore, leaf S concentration was enhanced in waterlogged plants treated with high-S, while anions were regulated whereby Cl− uptake was decreased. However, under control conditions, high-S did not provide additional benefits of improved plant growth, yield, and antioxidant activities compared to the medium-S application. Thus, it is concluded that additional S supplementation mitigates the adverse effects of waterlogging stress on oilseed rape, and needs to be employed as a potential strategy to alleviate the negative effects of this abiotic stress.

Elevated CO2 concentration regulate the stomatal traits of oilseed rape to alleviate the impact of water deficit on physiological properties

There is a limited understanding of how stomatal distribution and structure affect photosynthesis under elevated CO2 concentrations (e[CO2]) and variable soil water environments. This study investigated the effects of e[CO2] on stomatal morphology and distribution, gas exchange and growth parameters of oilseed rape plants under water deficit [soil moisture decreased from 80% field capacity (FC) (W; full irrigation) to 60% FC (D1), 40% FC (D2), and < 35% FC (D3)] and re-watering conditions in growth chambers with [CO2] controlled at 400 µmol mol−1 (a[CO2]) or 800 µmol mol−1 (e[CO2]). e[CO2] had a strong CO2 fertilization effect on the net photosynthetic rate (An) and growth of plants under water deficit. Under a[CO2], stomatal density and aperture on the adaxial leaf surface increased when soil moisture decreased from W to D1, while the stomatal aperture and regularity of the spatial distribution pattern of stomata decreased with decreasing soil moisture. Stomatal conductance (gs) were 47.1% and 26.1% capacity of anatomically determined maximum anatomical conductance (gsmax) with W under a[CO2] and e[CO2], respectively. e[CO2] enhanced plant recovery after re-watering through modifying stomatal traits. This study offers insights into the trade-off between stomatal traits and gas exchange for adapting plants to future climates.

Evaluation of Ethanedinitrile as a Potential Fumigant against Plasmodiophora brassicae, the Clubroot Pathogen

Clubroot, caused by Plasmodiophora brassicae Woronin, is one of the most challenging diseases to control in oilseed rape (Brassica napus L.) and other crucifers globally. Ethanedinitrile (EDN) is a promising fumigant shown to be effective against various pests and soil-borne pathogens. However, its efficacy against P. brassicae is yet to be tested. Therefore, the current study is focused on evaluating the effectiveness of EDN against P. brassicae at different rates, applied for different durations of exposure. Clubroot-susceptible oilseed rape plants, grown in fumigated soil, were evaluated for disease severity and growth parameters in greenhouse conditions. EDN exhibited good efficacy against the pathogen, with 81.39% disease suppression compared to the control. Complete control of the disease was achieved at the rates of 42 g/m3 and 50 g/m3 as well as in the treatment variant of 35 g/m3-48 h. In addition, EDN improved plant health by increasing shoot weight by 58.24%. However, the combination of a prolonged fumigation period and higher rates resulted in a decline in the seedling emergence rate and plant shoot weight, indicating a potential adverse residual effect of higher rates and longer durations of exposure in plants.

Examining spray-induced gene silencing for pollen beetle control

Pollen beetles are a transcontinental threat to oilseed rape cultivation. Conventional insecticide use has resulted in resistance development, and can furthermore lead to losses of non-target organisms, including those that contribute to natural biological control of pollen beetle populations. Biosafe alternatives to synthetic pesticides must be explored. Double-stranded RNA (dsRNA) targeting pollen beetle, by the RNA interference (RNAi) mode of action, has been previously demonstrated under laboratory conditions. The present study examined, under a whole plant context, the potential for spray-induced gene silencing (SIGS) in pollen beetle. We confirmed translocation of sprayed dsRNA to later-emerging, non-sprayed dietary tissues of oilseed rape, as well as infiltration of sprayed dsRNA to the inner tissues of reproductive buds (pollen beetle’s food source). No effect on survival was observed. The inefficacy of SIGS observed here highlights the requirement for more effective SIGS approaches to pollen beetle management. The translocation of sprayed dsRNA within oilseed rape plants, and the non-significant yet detectable effect on target mRNA downregulation, together suggest potential for future optimization of a SIGS approach against pollen beetle.

Yield Loss and Integrated Disease Control of Rhizoctonia solani AG2-1 Using Seed Treatment and Sowing Rate of Oilseed Rape.

Rhizoctonia solani anastomosis group (AG) 2-1 is an ubiquitous soilborne pathogen causing severe damping-off of oilseed rape (OSR). In the absence of varietal resistance to AG2-1, there are limited methods for integrated disease management. The objectives of these field studies were to quantify yield losses due to AG2-1 and to determine the effectiveness of integrated control using sedaxane, fludioxonil, and metalaxyl-M applied as seed treatment on two OSR genotypes at a sowing rate of 40 (low) or 80 (high) seeds m-2. Crop assessments of green area index (GAI), vigor, and cabbage stem flea beetle (CSFB) Psylliodes chrysocephala damage were carried out at GS16, while pathogen DNA in soil was quantified using real-time PCR at GS32. Yield and seed weight losses of 41 and 18%, respectively, were associated with reduced establishment, GAI, vigor, and delayed development and flowering of OSR. Seed treatment reduced AG2-1 DNA in soil by 80%, resulting in a 94, 16, and 64% increase of establishment, thousand seed weight (TSW), and yield, respectively. Seed treatment also mitigated the effects of AG2-1 on delaying plant development, resulting in increased uniformity of crop flowering. OSR plants infected with AG2-1 suffered 27% more damage by the CSFB, indicating positive pathogen-pest interaction at the expense of the OSR host. Optimum control of AG2-1 infection was achieved by integrating low sowing rate and seed treatment. However, under dual pest and pathogen attack, high sowing rates should be combined with the use of seed treatment to mitigate seedling death and delayed development caused by AG2-1 and CSFB damage.