Oilseed Rape Crops Research Articles

Weed Hosts Represent an Important Reservoir of Turnip Yellows Virus and a Possible Source of Virus Introduction into Oilseed Rape Crop.

Turnip yellows virus (TuYV) is one of the most important pathogens of oilseed rape worldwide. The virus has a large host range including many crop species (e.g., oilseed rape, pea, chickpea) and weeds from more than twenty plant families. Other than oilseed rape, we detected TuYV in many commonly grown weed species that share the fields and vegetation period together with canola crops in Czech and Slovak Republics. TuYV was detected by reverse-transcription polymerase chain reaction (RT-PCR) in at least 26 species including main crop hosts (oilseed rape), intercrops and weeds such as Amaranthus retroflexus, Atriplex patula (Amaranthaceae), Arctium lappa, Lactuca serriola, Taraxacum officinale, Tripleurospermum inodorum (Asteraceae), Phacelia tanacetifolia (Boraginaceae), Brassica napus, Capsella bursa-pastoris, Descurainia Sophia, Raphanus raphanistrum, Sinapis alba, Sisymbrium officinale, Thlaspi arvense (Brassicaceae), Silene alba, Stellaria media (Caryophyllaceae), Euphorbia helioscopia (Euphorbiaceae), Geranium rotundifolium (Geraniaceae), Lamium purpureum (Lamiaceae), Fumaria officinalis, Papaver rhoeas (Papaveraceae), Veronica persica (Plantaginaceae syn. Scrophulariaceae), Fallopia convolvulus (Polygonaceae), Solanum nigrum (Solanaceae), Urtica dioica (Urticaceae) and Viola arvensis (Violaceae). The detection of TuYV was further confirmed by RT-qPCR as well as Sanger sequencing of the PCR fragments. We discovered four new weed species as hosts of TuYV such as T. inodorum, S. alba, G. rotundifolium and E. helioscopia, representing their three respective plant families. The readthrough domain (RTD) gene sequence analysis of the Czech and Slovak TuYV isolates from oilseed rape and weed species showed similar within-group nucleotide divergence (7.1% and 5.6%, respectively) and the absence of geographical- or host-based phylogenetic clustering. The high-throughput sequencing of the P. rhoeas sample enabled the obtention of a nearly complete genome of TuYV and revealed the mixed infection of TuYV with turnip mosaic virus and cucumber mosaic virus. Our results thus show that weed species are an important TuYV reservoir and play a significant role in the spread and incidence of the disease in field crops such as oilseed rape.

Effect of No-Tillage Management on Soil Organic Matter and Net Greenhouse Gas Fluxes in a Rice-Oilseed Rape Cropping System

No-tillage (NT) management is considered a leading approach for sustaining crop production and improving soil and environmental quality. Based on a long-term no-tillage experiment in a rice–oilseed rape cropping system, we examined differences in soil organic matter (SOM), soil microbial carbon (C) and nitrogen (N) content, and methane (CH4) and carbon dioxide (CO2) fluxes between NT and conventional tillage (CT) management. SOM under NT was 21.0 g kg–1, and a significant difference was detected between 2004 and 2016. SOM increased under NT and CT by averages of 0.60 and 0.32 g kg–1 year–1, respectively. Soil microbial C and N content were higher under CT than under NT. However, soil C:N ratios under NT were 17.4 and 9.7% higher than the CT, respectively, whereas soil microbial C:N ratios under NT were on average 9.47 and 9.70% higher. In addition, about 70% of CO2 net uptake and over 99% of net CH4 emissions occurred during the rice season in May–September in the rice–oilseed rape cropping system. Annual cumulative CH4 and daytime net ecosystem CO2 exchange (NEE) under NT was 1813.9 g CO2 equiv. m–2, 10.8% higher than that under CT. Our results suggest that a higher soil microbial C:N ratio and NEE (CH4 and daytime CO2) could contribute to increasing SOM/C in the surface soil under NT management.

Cross-protection of oilseed rape against Verticillium longisporum by the non-aggressive lineage A1/D2

Verticillium longisporum is a soil-borne vascular pathogen of oilseed rape and other Brassica crops. The limited availability of chemical control measures against vascular pathogens calls for the exploration of control alternatives. Cross-protection may be conveyed by the use of non-pathogenic or non-aggressive isolates of potential pathogens as biocontrol agents. V. longisporum consists of three lineages that originated from three independent hybridization events of four haploid Verticillium parents. Previous pathogenicity tests in the greenhouse have shown that lineage A1/D2 is non-pathogenic or non-aggressive on different Brassica and non-Brassica hosts. Thus, the cross-protection potential of the A1/D2 lineage against an aggressive V. longisporum isolate in oilseed rape was tested. With root-dip inoculation, A1/D2 reduced disease symptoms when applied before or at the same time as the aggressive isolate. The induction of salicylic acid, a signal known to play a role in basal and cultivar-related resistance, was not involved in the biocontrol mechanism. The most practical and best feasible method of application as a seed coat failed to confirm the biocontrol effect of A1/D2 observed with root-dip inoculation. Confocal microscopy analysis revealed that seed coating led to insufficient A1/D2 hyphal establishment on the roots compared to root-dip inoculation, which may explain the lack of a biocontrol effect after seed coating and illustrates the importance of the application method for efficacy of a cross-protective biocontrol agent.

New Control Methods Against the Cabbage Stem Flea Beetle in Oilseed Rape Crops

Cabbage stem flea beetle (CSFB) is one of the most damaging pests of oilseed rape (OSR) grown in the UK. An intensive research effort is underway in the UK and throughout OSR growing regions of continental Europe to develop new control methods for this pest. In the first article of a series of three, we review this research and consider approaches to this pest problem that may be available immediately and in the short-term. Agronomic practices (sowing date, seed rate, crop defoliation, companion crops, etc) are being investigated and several of these approaches are already being used on farm. The use of physically acting biopesticides such as fatty acids, while not yet being used may also provide an effective solution and could be available in the short-term. Each of these approaches has the potential to form part of future Integrated Pest Management (IPM) programmes but importantly none should be seen as simple replacements for conventional synthetic insecticides. Solutions that may be available in the medium and longer-term will be discussed in the next articles. The cabbage stem flea beetle (CSFB), Psylliodes chrysocephala (Coleoptera: Chrysomelidae) is one of the most important pests of winter OSR crops in central and northern European countries. The adult beetle causes 'shot holing' feeding damage on cotyledons and true leaves of young winter OSR plants in late summer-early autumn. The larvae feed inside petioles and stems of the plants, causing additional damage. The focus on making food production more environmentally friendly means reduced chemical inputs, protecting nontarget species and overall biodiversity. This led to the withdrawal of systemic synthetic neonicotinoid pesticide seed treatments in many crops (oilseed rape included) in 2013. Since the withdrawal of neonicotinoid seed treatments, there has been a reliance on pyrethroid insecticides. This has been seen with a shift in the use of insecticides in oilseed rape, with CSFB the target for 28% of insecticide applications in 2012 (before neonicotinoid seed treatments were withdrawn) to 75% in 2020. The result of this shift has been the development of resistance to this group of insecticides in CSFB population. This situation has become so severe that some UK populations of CSFB are now 100% resistant to the pyrethroid insecticide lambda-cyhalothrin. These changes have led to the area of oilseed rape grown in the UK being halved (756,000 hectares in 2012 versus 307,000 hectares in 2021), with growers citing CSFB as one of the main reasons for this decrease. At the same time, the number of insecticide spray rounds has increased from two to three between 2012 and 2020, with these applications dominated by the use of pyrethroids. The most widely used pyrethroid insecticide, lambda-cyhalothrin, has also increased as a proportion of the insecticide-treated area from 32% in 2012 to 76% in 2020. Additional surveys by Fera, completed as part of the CropMonitor information service, between 2009 and 2020 show that the number of CSFB larvae per plant increased from an average of 0.5 larvae per plant in the years before the withdrawal of neonicotinoids, to more than 2 larvae per plant the following year in 2014 in East England, and almost 5 larvae per plant in 2019 in the South West of England. Here we present solutions that are currently available or that could be made available in the short-term. We consider how each of these approaches could be used in Integrated Pest Management (IPM) programmes.

Clopyralid applied to winter oilseed rape (Brassica napus L.) contaminates the food products nectar, honey and pollen

Clopyralid is a systemic herbicide used in oilseed rape and other crops. It was found in Danish honey from 2016 in concentrations exceeding the maximum residue level (MRL) of 0.05 mg kg−1. About 50% of the Danish honey is based on nectar from winter oilseed rape. In 2019 and 2020, winter oilseed rape fields were sprayed with clopyralid just before the assigned spraying deadline. At flowering, nectar and pollen samples were collected and the content of clopyralid was measured. Honey and pollen samples were also collected from beehives next to ten conventional winter oilseed rape fields sprayed with clopyralid. Clopyralid was found in nectar and pollen from the experimental fields, and in honey and pollen from beehives next to the conventional fields. For most samples the content in nectar and honey exceeded the MRL. The concentrations found, may not pose any health risk for consumers, as the MRL is based on the original detection limit and not on toxicological tests. However, it can have a significant economical consequence for the beekeepers, who are not allowed to sell the honey if the concentration of clopyralid exceeds 0.1 mg kg−1. Reducing the acceptable applicable rate of clopyralid or implementing an earlier deadline for spraying of clopyralid may reduce the risk of contaminating bee food products. However, if it is not possible to obtain a satisfactory effect of clopyralid on the weed flora under these conditions, spraying with pesticides containing clopyralid should be restricted in winter oilseed rape. Determination of an MRL value based on toxicological tests might result in a higher value and make it acceptable selling the honey containing higher levels of clopyralid.

Problems in cabbage stem weevil control (Ceutorhynchus pallidacytlus Marsh.) in winter oilseed rape

Due to the length of egg-laying period (> 80 days), two applications of insecticides against cabbage stem weevil (Ceutorhynchus pallidactylus Marsh.) are currently needed. However, resistance of pollen beetle (Brassicogethes aeneus F.) to pyrethroids complicates the choice of suitable insecticide for the second application. The active ingredients cypermethrin, etofenprox, pymetrozine, indoxacarb and chlorpyrifos-ethyl applied as second spring applications to winter oilseed rape crops were assessed under field conditions from 2016 to 2018 to ascertain how they could reinforce the effects of the first spring application (beta-cyfluthrin) on cabbage stem weevil. Chlorpyrifos-ethyl and etofenprox strengthened the effects of the first spring spray on cabbage stem weevil markedly more than cypermethrin. Pymetrozine and indoxacarb, effective on resistant populations of pollen beetles, showed the lowest contribution to increase the effects. Indoxacarb showed a low effect on C. pallidactylus in laboratory tests too. The impacts of the bans on active ingredients chlorpyrifos-ethyl and pymetrozine are discussed.

Stereo-vision-based multi-crop harvesting edge detection for precise automatic steering of combine harvester

With the development of the intelligent combine harvesters, the whole-field automatic harvesting has become feasible and includes driving straight along the unharvested crop edge and steering in the crop headland. Detecting the unharvested crop edge and the end of the cultivation crop, is the foundation of whole-field automatic harvesting. A rapid and robust detection method for detecting the harvesting edge for multiple crops based on stereo vision was developed. In order to improve the processing speed and keep the crop harvesting edge within the target region, a dynamic ROI (region of interest) extraction algorithm based on HSV (hue, saturation, and value) space scanning was developed. A coordinate transformation method was applied to generate a crop elevation image, and the unharvested crop area was obtained by the Ostu algorithm. Simultaneous detection of unharvested crop edge and crop end edge was realised by the method based on the horizontal length feature of the unharvested area contour. This enabled automatic driving along the unharvested crop edge, and automatic steering into the next harvest path according to the crop end edge. Finally, field tests with crops of paddy, oil-seed rape, and maize crops were carried out to test the system performance, and the accuracy of the detection was found to be higher than 98% for paddy and rape, and higher than 94% for maize with an average processing speed of 49 ms frame−1. The experiments showed that the proposed method exhibited high accuracy and efficiency and was suitable for various complex field environments.

Climate Overrides Effects of Fertilizer and Straw Management as Controls of Nitrous Oxide Emissions After Oilseed Rape Harvest

Oilseed rape (Brassica napus L.) is an important bioenergy crop that contributes to the diversification of renewable energy supply and mitigation of fossil fuel CO2 emissions. Typical oilseed rape crop management includes the use of nitrogen (N) fertilizer and the incorporation of oilseed rape straw into soil after harvest. However, both management options risk increasing soil emissions of nitrous oxide (N2O). The aim of this 2-years field experiment was to identify the regulating factors of N cycling with emphasis on N2O emissions during the post-harvest period. As well as the N2O emission rates, soil ammonia (NH4+) and nitrate (NO3−) contents, crop residue and seed yield were also measured. Treatments included variation of fertilizer (non-fertilized, 90 and 180 kg N ha−1) and residue management (straw remaining, straw removal). Measured N2O emission data showed large intra- and inter-annual variations ranging from 0.5 (No-fert + str) to 1.0 kg N2O-N ha−1 (Fert-180 + str) in 2013 and from 4.1 (Fert-90 + str) to 7.3 kg N2O-N ha−1 (No-fert + str) in 2014. Cumulative N2O emissions showed that straw incorporation led to no difference or slightly reduced N2O emissions compared with treatments with straw removal, while N fertilization has no effect on post-harvest N2O emissions. A process-based model, CoupModel, was used to explain the large annual variation of N2O after calibration with measured environmental data. Both modeled and measured data suggest that soil water-filled pore space and temperature were the key factors controlling post-harvest N2O emissions, even though the model seemed to show a higher N2O response to the N fertilizer levels than our measured data. We conclude that straw incorporation in oilseed rape cropping is environmentally beneficial for mitigating N2O losses. The revealed importance of climate in regulating the emissions implies the value of multi-year measurements. Future studies should focus on new management practices to mitigate detrimental effects caused by global warming, for example by using cover crops.

Green Manure Amendment Can Reduce Nitrogen Fertilizer Application Rates for Oilseed Rape in Maize-Oilseed Rape Rotation.

Excessive use of chemical fertilizers has led to a reduction in the quality of arable land and environmental pollution. Using green manure to replace chemical fertilizers is one of the most effective solutions. To study the effect of green manure on the requirement for nitrogen fertilizer in oilseed rape, a field experiment with maize–oilseed rape rotation was conducted. Green manure was intercropped between rows of maize and returned after the maize harvest, with no green manure intercropped as control. Different nitrogen fertilizer treatments (0, 65%, 75% and 100% N rates, respectively) were applied during the oilseed rape season. The results showed that with a 35% reduction in nitrogen application rate, the rapeseed grain yield was significantly higher with the maize intercropping with green manure returned to the field than with the maize monocropping treatment at the same nitrogen level. Under conditions of intercropping and return of green manure, compared with the full standard rate of nitrogen fertilizer treatment, a reduction in nitrogen application of 25–30% in the rape season had no significant effect on rape yield. The agronomic efficiency of nitrogen fertilizer on oilseed rape increased significantly, by 47.61–121%, with green manure incorporation. In addition, green manure incorporation significantly increased the soil organic matter content and the soil-available nitrogen content when chemical nitrogen fertilization was abandoned. Benefit analysis showed that a 25–35% reduction in chemical nitrogen fertilizer applied to oilseed rape crops could be achieved by intercropping green manure in the maize season before the sowing of rapeseed in the experimental area. In the long-term, this measure would increase nitrogen utility, reduce production costs, and have concomitant environmental benefits of improving the quality of cultivated land.

Greenhouse Gas Emissions and Crop Yields From Winter Oilseed Rape Cropping Systems are Unaffected by Management Practices

Winter oilseed rape is traditionally established via plough-based soil cultivation and conventional sowing methods. Whilst there is potential to adopt lower cost, and less intensive establishment systems, the impact of these on greenhouse gas emissions have not been evaluated. To address this, field experiments were conducted in 2014/2015 and 2015/2016 to investigate the effects of 1) crop establishment method and 2) sowing method on soil greenhouse gas emissions from a winter oilseed rape crop grown in Ireland. Soil carbon dioxide, nitrous oxide and methane emission measurements were carried out using the static chamber method. Yield (t seed ha−1) and the yield-scaled global warming potential (kg CO2-eq. kg−1 seed) were also determined for each management practice. During crop establishment, conventional tillage induced an initially rapid loss of carbon dioxide (2.34 g C m−2 hr−1) compared to strip tillage (0.94 g C m−2 hr−1) or minimum tillage (0.16 g C m−2 hr−1) (p < 0.05), although this decreased to background values within a few hours. In the crop establishment trial, the cumulative greenhouse gas emissions were, apart from methane, unaffected by tillage management when sown at a conventional (125 mm) or wide (600 mm) row spacing. In the sowing method trial, cumulative carbon dioxide emissions were also 21% higher when plants were sown at 10 seeds m−2 compared to 60 seeds m−2 (p < 0.05). Row spacing width (125 and 750 mm) and variety (conventional and semi-dwarf) were found to have little effect on greenhouse gas emissions and differences in seed yield between the sowing treatments were small. Overall, management practices had no consistent effect on soil greenhouse gas emissions and modifications in seed yield per plant countered differences in planting density.

Unmanned aerial vehicle-based field phenotyping of crop biomass using growth traits retrieved from PROSAIL model

Unmanned aerial vehicle (UAV) platform has been perceived as a useful tool for high-throughput field phenotyping of crop growth traits. While interpretation of UAV image data and retrieval of reliable and accurate phenotypic information are still challengeable due to the variations in sensors, crops and environment conditions. The aim of this study, therefore, is to explore the potential of UAV-based field phenotyping with the PROSAIL model to estimate biomass of rice and oilseed rape crops. Field experiments were designed for rice and oilseed rape with different nitrogen (N) treatments, and a UAV platform mounted with a multispectral camera was used to collect multi-temporal field images. Simultaneously, field measurements of leaf chlorophyll content (Cab), leaf area index (LAI), canopy chlorophyll content (CCC) and biomass were conducted. The results showed that coupling UAV-based multispectral images at the spectral region of 604–872 nm with the PROSAIL model successfully retrieved Cab, LAI and CCC of rice with the root mean square error (RMSE) of 5.40 μg/cm2, 1.13, and 43.50 μg/cm2, respectively. Further, the Cab, LAI and CCC retrieved from the PROSAIL model achieved the satisfactory biomass estimation in rice with the RMSE of 0.32 kg/m2, 0.23 kg/m2 and 0.22 kg/m2, respectively, which was comparable or superior to those obtained from commonly used empirical models. The proposed method also presented the robust performance for rice biomass estimation at different growth stages. In addition, model validation with the oilseed rape dataset showed an acceptable accuracy of biomass estimation with the determination coefficient (r2), RMSE and relative RMSE of 0.81, 0.03 kg/m2 and 27.82%, respectively, and still outperformed the empirical models with the better estimation performance. These findings demonstrate the potential of the proposed biomass retrieval strategy for UAV-based multispectral images, which also extend the application of PROSAIL model in field phenotyping of crop growth traits.

Anther-Feeding-Induced RNAi in Brassicogethes aeneus Larvae

The biosafety aspect of applying double-stranded RNA (dsRNA) in crop pest management is rooted in dsRNA's mode of action, which displays nucleotide sequence-specificity to a particular region of a messenger RNA (mRNA), against which the insecticidal dsRNA is designed. This prominent and promising class of insecticides therefore has the potential to target a single pest species while conferring negligible effect on non-target organisms. Recent studies examining the effect of target-specific dsRNA in adults of the pollen beetle Brassicogethes aeneus, a major pest of oilseed rape (Brassica napus) crops in Europe, suggest the potential for developing a gene-silencing approach within integrated B. aeneus management. The present study examines the efficacy of target-specific dsRNA on target-mRNA silencing, and subsequent gene-silencing-induced mortality, in B. aeneus larvae, as this life stage represents a critical target for achieving optimal integrated B. aeneus control. Treatment applications occurred via feeding on dsRNA-treated anthers for 3 d. We observed variable gene-silencing efficacy, all target treatments having a significant or marginally significant effect after 3 d of dsRNA feeding, with greater variability at 6 d. These results further validated significant gene-silencing-induced mortality observed for one of the target treatments. Moreover, gene-silencing-induced mortality occurred at a quicker rate in B. aeneus larvae compared to what has been previously observed in B. aeneus adults. Finally, we consider refinements that must be made to B. aeneus larval bioassay setups to promote and strengthen future larval studies regarding this important crop pest species.

Influence of Soil-Borne Inoculum of Plasmodiophora brassicae Measured by qPCR on Disease Severity of Clubroot-Resistant Cultivars of Winter Oilseed Rape (Brassica napus L.).

Use of resistant cultivars is considered the most effective tool in managing clubroot. Three clubroot-resistant commercial winter oilseed rape (OSR) cultivars and a susceptible ‘Cultivar mix’ were evaluated for disease severity index (DSI) and yield performance in field soils, selected for varying abundance of natural inoculum of Plasmodiophora brassicae. Seven field trials were carried out during 2017–2019 in winter OSR crops, and comparative bioassays were performed in a growth chamber. Substantial variation in clubroot infection between years was observed in the field trials. For Cultivar mix, a negative correlation (y = −252.3ln(x) + 58,897.6) was found between inoculum density and seed yield in five trials, whereas no correlation was found for the resistant cultivars. In bioassays, Cultivar mix exhibited a significantly high correlation between DSIb and number of gene copies g−1 soil (R2 = 0.72). For resistant cvs., Mentor and Alister, correlation was R2 = 0.45 and 0.58, respectively, indicating that resistance was under pressure. In field trials, DSIf of the resistant cultivars was lower (<27). The recommendation is thus to use clubroot-resistant cultivars of OSR as part of Integrated Pest Management in situations where abundance of P. brassicae DNA exceeds 1300 gene copies g−1 soil.

Mitigation of yield-scaled nitrous oxide emissions and global warming potential in an oilseed rape crop through N source management

Enhanced-efficiency nitrogen (N) fertilizers, such as those containing nitrification or urease inhibitors, can mitigate the carbon (C) footprint linked to the production of bioenergy crops through a reduction in direct nitrous oxide (N2O) emissions and indirect N2O losses. These indirect emissions are derived from ammonia (NH3) volatilization, which also have important environmental and health implications. The evaluation of the global warming potential (GWP) of different N sources using site-specific data of yield and direct and indirect emissions is needed for oilseed rape under rainfed semi-arid conditions, especially when meteorological variability is taken into account. Using urea as a N source, the N2O mitigation efficacy of the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) alone or combined with the nitrification inhibitor 2-(3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) was evaluated under field conditions in a rainfed oilseed rape (Brassica napus L.) crop. Two additional N sources from calcium ammonium nitrate (CAN), with and without DMPSA, were included. The GWP of the treatments was estimated considering the emissions from inputs, operations and other direct and indirect emissions of greenhouse gases (GHGs), such as methane (CH4) and the volatilization of NH3. We also measured the abundance of key genes involved in nitrification and denitrification to improve the understanding of N2O emissions on a biochemical basis under the conditions of our study. The results show that due to the intense rainfall after fertilization and a rewetting event, N2O losses from fertilizers without inhibitors were greater than those previously reported under Mediterranean conditions, while NH3 losses were low and not affected by the urease inhibitor. The cumulative N2O emissions (which were greatly influenced by a rewetting peak three months after fertilization) from the urea fertilization were significantly higher than those from CAN. The presence of NBPT significantly reduced N2O losses by an average of 71%, with respect to urea. The use of DMPSA with CAN resulted in an abatement of N2O emissions (by 57%) and a significant increase in oil yield in comparison with CAN alone. All inhibitor-based treatments were effective in abating N2O emissions during the rewetting peak. The abundances of the nitrifier and denitrifier communities, especially ammonia-oxidizing bacteria (AOB), significantly decreased relative to the urea or CAN treatments as inhibitors were applied. Under the conditions of our study, the sustainability of a bioenergy crop such as oilseed rape can be improved by using inhibitors because they mitigated N2O emissions and/or enhanced the oil yield.

MULTISPECTRAL SHEET DIAGNOSTICS OF TECHNOLOGICAL STRESSES ON WINTER RAPES CROPS

Technological stresses are an urgent challenge for winter crops and in particular rapeseed in industrialproduction and in the mass use of agrochemicals and plant protection products. Effective resuscitationmeasures are possible only in the initial stages of the growing season and require reliable and accessibleinformation about the condition of crops. The purpose of the work is to develop an index based on the resultsof analysis of multispectral images with high spatial resolution, obtained by UAVs for the identificationof technological stresses. During field research on October 30, 2019, it was found that in the affected areas,the plants have an abnormal color of the two lower leaves, namely yellow and red. To identify affectedplants, it was proposed to use an image of the object based on the ratio of several channels simultaneously, which allow to distinguish between affected and healthy plants, soil and leaves of abnormal color. Itis proposed to use the RRL (rape red leaf) indices, which are an indicator of the technological nature ofstress, namely RRLgr, designed exclusively for the optical range and the RRLm index (green — G, red — R,border red — Re and near infrared — NIR). Such indices are convenient for monitoring the condition ofrapeseed crops and automated data processing. It was found that when monitoring rapeseed crops in thegrowing season of 6–8 leaves affected by technological stress, using Slantrange 3p height of 100 m, for the indices RRLgr and RRLm is characterized by abnormal leaf color, which was recorded in 1.5 and 2.1%of the total area of plants on the site, respectively. The use of multispectral analysis makes it possible todifferentiate the identification of technological stresses with different manifestations of impression. Ata standard flight altitude for Slantrange 3p of 100 m with the fixation of anomalous color in 1.5% of thetotal area of winter oilseed rape plants is the basis for the organization of additional ground inspection ofthe identified areas of winter oilseed rape crops.

Molecular characterization of poleroviruses isolated from oilseed rape in Greece.

In 2018 virus-like symptoms, typical of polerovirus infection were observed in several oilseed rape crops in northern Greece. In order to identify the etiological agent of these symptoms a polerovirus-generic RT-PCR assay was applied. Sequencing of the amplicons revealed the presence of virus isolates genetically close to turnip yellows virus (TuYV). Further molecular characterization of the near complete genome of '1-2', 'Geo1', 'Geo7' and 'Geo15' isolates revealed that they share > 96% nt identity with various TuYV sequences. On the other hand, the fifth, characterized isolate from oilseed rape, termed '1-1', showed higher sequence similarity to brassica yellows virus (BrYV) regarding the 5' part of the complete coding sequence, whereas the 3' part was closely related to TuYV isolates. A recombination analysis using RDP indicated the presence of a putative breakpoint (nucleotide position 2964) in '1-1' genome and it is proposed that the virus isolate '1-1' might be an interspecies recombinant between BrYV and TuYV. To our knowledge, this is the first time that the complete coding sequences of Greek TuYV isolates have been determined and the first detection of a BrYV/TuYV recombinant isolate infecting oilseed rape in Greece.

High genetic diversity and strong genetic structure of Strongyllodes variegatus populations in oilseed rape production areas of China

BackgroundStrongyllodes variegatus (Fairmaire) is a major insect pest of oilseed rape in China. Despite its economic importance, the contribution of its population genetics in the development of any suitable protection control strategy for the management of oilseed rape crops is poorly studied. It is a much urgent need to prevent its spread to the rest of the world.ResultsUsing the sequences of mitochondrial DNA cytochrome c oxidase subunit I (COI) and cytochrome b (Cytb) as genetic markers, we analyzed the population genetic diversity and structure of 437 individuals collected from 15 S. variegatus populations located in different oilseed rape production areas in China. In addition, we estimated the demographic history using neutrality test and mismatch distribution analysis. The high level of genetic diversity was detected among the COI and Cytb sequences of S. variegatus. The population structure analyses strongly suggested three distinct genetic and geographical regions in China with limited gene flow. The Mantel test showed that the genetic distance was greatly influenced by the geographical distance. The demographic analyses showed that S. variegatus had experienced population fluctuation during the Pleistocene Epoch, which was likely to be related to the climatic changes.ConclusionOverall, these results demonstrate that the strong genetic structure of S. variegatus populations in China, which is attributed by the isolation through the geographical distance among populations, their weak flight capacity and subsequent adaptation to the regional ecological conditions.

Optimising drip irrigation and fertigation schedules for higher crop and water productivity of oilseed rape (Brassica napus L.)

Drip irrigation and fertigation, being advocated for higher crop and water productivity require optimization of irrigation and fertilization schedules. Field experiments were conducted during 2016–2018 to evaluate water and energy-efficient drip irrigation and fertigation schedules for higher productivity and profitability from oilseed rape. The treatments comprised of a combination of three levels of drip irrigation {60, 80 and 100% of cumulative pan-evaporation (CPE)} and three levels of fertigation {60, 80 and 100% recommended dose of fertilizers (RDF)} along with one absolute control (flood irrigation and soil application of RDF). The yields of crop under drip irrigation at 100 and 80% of CPE were statistically similar but significantly higher than irrigation at 60% of CPE. The irrigation use efficiency (IUE) and water use efficiency (WUE) were maximum at 80% of CPE followed by 100 and 60% of CPE. Drip irrigation at 80% of CPE resulted in 18% higher yield along with a water-saving of 35.4% than absolute control. Energy use efficiency (EUE) was higher at 100% of CPE followed by 80 and 60% of CPE. Whereas, energy productivity at 100 and 80% of CPE being statistically similar but significantly higher than 60% of CPE. Highest benefit: cost (B:C) ratio and net returns were obtained with drip irrigation at 100% of CPE and lowest at 60% of CPE. Fertigation at 100 and 80% RDF recorded significantly higher seed yield than 60% RDF and absolute control.

Identification of microbial signatures linked to oilseed rape yield decline at the landscape scale

BackgroundThe plant microbiome plays a vital role in determining host health and productivity. However, we lack real-world comparative understanding of the factors which shape assembly of its diverse biota, and crucially relationships between microbiota composition and plant health. Here we investigated landscape scale rhizosphere microbial assembly processes in oilseed rape (OSR), the UK’s third most cultivated crop by area and the world's third largest source of vegetable oil, which suffers from yield decline associated with the frequency it is grown in rotations. By including 37 conventional farmers’ fields with varying OSR rotation frequencies, we present an innovative approach to identify microbial signatures characteristic of microbiomes which are beneficial and harmful to the host.ResultsWe show that OSR yield decline is linked to rotation frequency in real-world agricultural systems. We demonstrate fundamental differences in the environmental and agronomic drivers of protist, bacterial and fungal communities between root, rhizosphere soil and bulk soil compartments. We further discovered that the assembly of fungi, but neither bacteria nor protists, was influenced by OSR rotation frequency. However, there were individual abundant bacterial OTUs that correlated with either yield or rotation frequency. A variety of fungal and protist pathogens were detected in roots and rhizosphere soil of OSR, and several increased relative abundance in root or rhizosphere compartments as OSR rotation frequency increased. Importantly, the relative abundance of the fungal pathogen Olpidium brassicae both increased with short rotations and was significantly associated with low yield. In contrast, the root endophyte Tetracladium spp. showed the reverse associations with both rotation frequency and yield to O. brassicae, suggesting that they are signatures of a microbiome which benefits the host. We also identified a variety of novel protist and fungal clades which are highly connected within the microbiome and could play a role in determining microbiome composition.ConclusionsWe show that at the landscape scale, OSR crop yield is governed by interplay between complex communities of both pathogens and beneficial biota which is modulated by rotation frequency. Our comprehensive study has identified signatures of dysbiosis within the OSR microbiome, grown in real-world agricultural systems, which could be used in strategies to promote crop yield.9LHMp6srYAP4ntBATPUdWaVideo abstract

Advances in automatic identification of flying insects using optical sensors and machine learning

Worldwide, farmers use insecticides to prevent crop damage caused by insect pests, while they also rely on insect pollinators to enhance crop yield and other insect as natural enemies of pests. In order to target pesticides to pests only, farmers must know exactly where and when pests and beneficial insects are present in the field. A promising solution to this problem could be optical sensors combined with machine learning. We obtained around 10,000 records of flying insects found in oilseed rape (Brassica napus) crops, using an optical remote sensor and evaluated three different classification methods for the obtained signals, reaching over 80% accuracy. We demonstrate that it is possible to classify insects in flight, making it possible to optimize the application of insecticides in space and time. This will enable a technological leap in precision agriculture, where focus on prudent and environmentally-sensitive use of pesticides is a top priority.