Impact of Sclerotinia Stem Rot on Yield of Canola

Current and potential pest threats for canola in the Canadian Prairies

Canola/oilseed rape (Brassica napus L.) production in Canada has increased to become a foundational crop in the Canadian Prairies and an important economic driver of this region. The increase in seeded area, and by association its reduction in-crop rotation frequency, has made it easier for pests to overcome current recommended agronomic management practices. The Canola Council of Canada has been successful in involving the entire commodity value chain in promoting and strengthening the Canadian canola industry; however, because of this production increase it is critically important to understand, evaluate and mitigate the potential risks of canola yield losses to current and potential pests. This Perspective provides an overview of what are currently the most damaging insects, pathogens and weeds to canola in the Canadian Prairies, potential future threats and opportunities farmers, agronomists and researchers can take to minimize these risks. © 2023 Society of Chemical Industry.

Effective Control of Sclerotinia Stem Rot in Canola Plants Through Application of Exogenous Hairpin RNA of Multiple Sclerotinia sclerotiorum Genes

Sclerotinia stem rot is a globally destructive plant disease caused by Sclerotinia sclerotiorum. Current management of Sclerotinia stem rot primarily relies on chemical fungicides and crop rotation, raising environmental concerns. In this study, we developed an eco-friendly RNA bio-fungicide targeting S. sclerotiorum. Six S. sclerotiorum genes were selected for double-stranded RNA (dsRNA) synthesis. Four genes, a chitin-binding domain, mitogen-activated protein kinase, oxaloacetate acetylhydrolase, and abhydrolase-3, were combined to express hairpin RNA in Escherichia coli HT115. The effect of application of total RNA extracted from E. coli HT115 expressing hairpin RNA on disease progressive and necrosis lesions was evaluated. Gene expression analysis using real-time PCR showed silencing of the target genes using 5 ng/µl of dsRNA in a fungal liquid culture. A detached leaf assay and greenhouse application of dsRNA on canola stem and leaves showed variation in the reduction of necrosis symptoms by dsRNA of different genes, with abhydrolase-3 being the most effective. The dsRNA from a combination of four genes reduced disease severity significantly (P = 0.01). Plants sprayed with hairpin RNA from four genes had lesions that were almost 30% smaller than those of plants treated with abhydrolase-3 alone, in lab and greenhouse assays. The results of this study highlight the potential of RNA interference to manage diseases caused by S. sclerotiorum; however, additional research is necessary to optimize its efficacy.

Functional genomics of Brassica napus: Progresses, challenges, and perspectives

Brassica napus, commonly known as rapeseed or canola, is a major oil crop contributing over 13% to the stable supply of edible vegetable oil worldwide. Identification and understanding the gene functions in the B. napus genome is crucial for genomic breeding. A group of genes controlling agronomic traits have been successfully cloned through functional genomics studies in B. napus. In this review, we present an overview of the progress made in the functional genomics of B. napus, including the availability of germplasm resources, omics databases and cloned functional genes. Based on the current progress, we also highlight the main challenges and perspectives in this field. The advances in the functional genomics of B. napus contribute to a better understanding of the genetic basis underlying the complex agronomic traits in B. napus and will expedite the breeding of high quality, high resistance and high yield in B. napus varieties.

Biobased, Macro-, and Nanoscale Fungicide Delivery Approaches for Plant Fungi Control

In this report, two polymeric matrix systems at macro and nanoscales were prepared for efficacious fungicide delivery. The macroscale delivery systems used millimeter-scale, spherical beads composed of cellulose nanocrystals and poly(lactic acid). The nanoscale delivery system involved micelle-type nanoparticles, composed of methoxylated sucrose soyate polyols. Sclerotinia sclerotiorum (Lib.), a destructive fungus affecting high-value industrial crops, was used as a model pathogen against which the efficacy of these polymeric formulations was demonstrated. Commercial fungicides are applied on plants frequently to overcome the transmission of fungal infection. However, fungicides alone do not persist on the plants for a prolonged period due to environmental factors such as rain and airflow. There is a need to apply fungicides multiple times. As such, standard application practices generate a significant environmental footprint due to fungicide accumulation in soil and runoff in surface water. Thus, approaches are needed that can either increase the efficacy of commercially active fungicides or prolong their residence time on plants for sustained antifungal coverage. Using azoxystrobin (AZ) as a model fungicide and canola as a model crop host, we hypothesized that the AZ-loaded macroscale beads, when placed in contact with plants, will act as a depot to release the fungicide at a controlled rate to protect plants against fungal infection. The nanoparticle-based fungicide delivery approach, on the other hand, can be realized via spray or foliar applications. The release rate of AZ from macro- and nanoscale systems was evaluated and analyzed using different kinetic models to understand the mechanism of AZ delivery. We observed that, for macroscopic beads, porosity, tortuosity, and surface roughness governed the efficiency of AZ delivery, and for nanoparticles, contact angle and surface adhesion energy were directing the efficacy of the encapsulated fungicide. The technology reported here can also be translated to a wide variety of industrial crops for fungal protection. The strength of this study is the possibility of using completely plant-derived, biodegradable/compostable additive materials for controlled agrochemical delivery formulations, which will contribute to reducing the frequency of fungicide applications and the potential accumulation of formulation components in soil and water.

A Mechanistic Model Accounting for the Effect of Soil Moisture, Weather, and Host Growth Stage on the Development of Sclerotinia sclerotiorum

The fungus Sclerotinia sclerotiorum causes serious losses to several agricultural crops worldwide. By using systems analysis, we retrieved the available knowledge concerning S. sclerotiorum from the literature and then analyzed and synthesized the data to develop a mechanistic, dynamic, weather-driven model for the prediction of epidemics on different crops. The model accounts for i) the production and survival of apothecia; ii) the production, dispersal, and survival of ascospores; iii) infection by ascospores; and iv) lesion onset. The ability of the model to predict the occurrence of apothecia was evaluated for epidemics observed with different climates, soil types, and host crops (soybean, white bean, and carrot) using independent data obtained from trials conducted in Ontario (Canada) in 1981, 1982, and from 1999 to 2002; in Michigan (U.S.A.) in 2015 and 2016; and in Wisconsin (U.S.A.) in 2016. The model showed 0.82 accuracy and 0.73 specificity in predicting the presence of apothecia, with a posterior probability of correctly predicting apothecia to be present or absent of 0.804 and 0.876, respectively. The model was also validated for its ability to predict disease progress on soybean and sunflower in Ontario in 1981 and 1982, in Manitoba (Canada) in 2001 and 2002, and in Michigan in 2015 and 2016. Comparison of model output with observations showed a concordance correlation coefficient of 0.948, and a root mean square error of 0.122. The model represents an improvement of previous S. sclerotiorum models and could be useful for making decisions on disease control.

Functional study of CYP90A1 and ALDH3F1 gene obtained by transcriptome sequencing analysis of Brassica napus seedlings treated with brassinolide

Sclerotinia disease and weeds of Brassica napus greatly reduce crop yields. However, brassinolides can improve the resistance of plants to sclerotinia diseases and herbicides. In this study, we investigated the effects of brassinolide on the occurrence, physiological indices, yield, and gene expression of Fanming No. 1 seeds under sclerotinia and glufosinate stress. The results showed that soaking of the seeds in 0.015% brassinolide for 6 h reduced the incidence of sclerotinia by 10%. Additionally, in response to glufosinate stress at the seedling stage, the enzyme activities of catalase and superoxide dismutase increased by 9.6 and 19.0 U/gFW/min, respectively, and the soluble sugar content increased by 9.4 mg/g, increasing the stress resistance of plants and yield by 2.4%. LHCB1, fabF, psbW, CYP90A1, ALDH3F1, ACOX1, petF, and ACSL were screened by transcriptome analysis. ALDH3F1 and CYP90A1 were identified as key genes. Following glufosinate treatment, transgenic plants overexpressing ALDH3F1 and CYP90A1 were found to be resistant to glufosinate, and the expression levels of the ALDH3F1 and CYP90A1 were 1.03-2.37-fold as high as those in the control. The expression level of ATG3, which is an antibacterial gene related to sclerotinia disease, in transgenic plants was 2.40-2.37-fold as high as that in the control. Our results indicate that these two key genes promote plant resistance to sclerotinia and glufosinate. Our study provides a foundation for further studies on the molecular mechanisms of rapeseed resistance breeding and selection of new resistant varieties.

Tissue-specific mRNA profiling of the Brassica napus-Sclerotinia sclerotiorum interaction uncovers novel regulators of plant immunity

White mold is caused by the fungal pathogen Sclerotinia sclerotiorum and leads to rapid and significant loss in plant yield. Among its many brassicaceous hosts, including Brassica napus (canola) and Arabidopsis, the response of individual tissue layers directly at the site of infection has yet to be explored. Using laser microdissection coupled with RNA sequencing, we profiled the epidermis, mesophyll, and vascular leaf tissue layers of B. napus in response to S. sclerotiorum. High-throughput tissue-specific mRNA sequencing increased the total number of detected transcripts compared with whole-leaf assessments and provided novel insight into the conserved and specific roles of ontogenetically distinct leaf tissue layers in response to infection. When subjected to pathogen infection, the epidermis, mesophyll, and vasculature activate both specific and shared gene sets. Putative defense genes identified through transcription factor network analysis were then screened for susceptibility against necrotrophic, hemi-biotrophic, and biotrophic pathogens. Arabidopsis deficient in PR5-like RECEPTOR KINASE (PR5K) mRNA levels were universally susceptible to all pathogens tested and were further characterized to identify putative interacting partners involved in the PR5K signaling pathway. Together, these data provide insight into the complexity of the plant defense response directly at the site of infection.

Genome-Wide Identification and Expression Analysis of nsLTP Gene Family in Rapeseed (Brassica napus) Reveals Their Critical Roles in Biotic and Abiotic Stress Responses

Non-specific lipid transfer proteins (nsLTPs) are small cysteine-rich basic proteins which play essential roles in plant growth, development and abiotic/biotic stress response. However, there is limited information about the nsLTP gene (BnLTP) family in rapeseed (Brassica napus). In this study, 283 BnLTP genes were identified in rapeseed, which were distributed randomly in 19 chromosomes of rapeseed. Phylogenetic analysis showed that BnLTP proteins were divided into seven groups. Exon/intron structure and MEME motifs both remained highly conserved in each BnLTP group. Segmental duplication and hybridization of rapeseed’s two sub-genomes mainly contributed to the expansion of the BnLTP gene family. Various potential cis-elements that respond to plant growth, development, biotic/abiotic stresses, and phytohormone signals existed in BnLTP gene promoters. Transcriptome analysis showed that BnLTP genes were expressed in various tissues/organs with different levels and were also involved in the response to heat, drought, NaCl, cold, IAA and ABA stresses, as well as the treatment of fungal pathogens (Sclerotinia sclerotiorum and Leptosphaeria maculans). The qRT-PCR assay validated the results of RNA-seq expression analysis of two top Sclerotinia-responsive BnLTP genes, BnLTP129 and BnLTP161. Moreover, batches of BnLTPs might be regulated by BnTT1 and BnbZIP67 to play roles in the development, metabolism or adaptability of the seed coat and embryo in rapeseed. This work provides an important basis for further functional study of the BnLTP genes in rapeseed quality improvement and stress resistance.

Scientific evidence of sustainable plant disease protection strategies for oilseed rape (Brassica napus) in Sweden: a systematic map

BACKGROUND

Oilseed rape (OSR; Brassica napus L.) is a highly valued crop for food, feed and industrial use. It is primarily grown in temperate climates, and over recent decades, its area of production and profitability have increased. Concurrently, several diseases negatively impact OSR production. Diseases caused by soil-borne pathogens, pose a risk of substantial yield loss since crop rotation schemes have become narrow as the time lapse between OSR crops in a field has been shortened. The aims of this paper were to provide an overview of plant protection measures available for OSR production and to identify knowledge gaps and areas where more research is needed.

METHODS

This systematic map builds on a previously published protocol and follows the ROSES reporting standard. The search strategy was developed in collaboration with stakeholders and designed to cover available scientific evidence for OSR disease management in climate zones relevant for Scandinavian crop production (Dfc, Dfb, Cfb and Cfa in the Köppen-Geiger climate classification). Five scientific databases were used to identify peer-reviewed literature, complemented by additional searches performed in grey literature. Articles were screened at three stages: the title, abstract and full text. The eligible publications included studies of OSR crops, and all measures to control crop disease in agricultural fields were considered eligible interventions. The comparator was intervention and no intervention, and the yield per unit area, disease suppression or an increase in crop quality were determined to be outcomes of interventions. A basic assessment of the experimental design of each study was performed to assess its eligibility. All articles were coded based on the following categories: the location and climate zone, disease, pathogen, intervention and management method, outcome and study design. Articles not reporting original data but judged to be relevant (i.e., review papers, books and notes of registration of cultivars) were saved in a separate category called "books, reviews and reports".

REVIEW FINDINGS

A total of 4633 articles were collected through systematic searches. After duplicates were removed, 3513 articles were included in the screening process. After screening at the title and abstract levels, 897 articles were evaluated at the full text level, and 118 articles comprised the studies that met the eligibility criteria of the systematic map. The country (Canada) and region (Europe) with the largest OSR crop production areas also contributed the highest number of articles. In total, 17 different diseases were reported, with black leg (syn. Phoma stem canker) being the most studied disease. Nineteen different intervention methods or management types were examined. Cultivar resistance and pesticide application were the most studied control measures.

CONCLUSION

We report scientific studies on plant disease protection measures for OSR based on field trials where the results are intended to be directly implemented in crop production management. The map clearly provides an overview of research progress throughout the time period chosen, and it identifies knowledge gaps regarding important diseases where only a few studies have been published, for example, diseases caused by viruses.

Genetic mapping and genomic prediction of sclerotinia stem rot resistance to rapeseed/canola (Brassica napus L.) at seedling stage

GWAS detected ninety-eight significant SNPs associated with Sclerotinia sclerotiorum resistance. Six statistical models resulted in medium to high predictive ability, depending on trait, indicating potential of genomic prediction for disease resistance breeding. The lack of complete host resistance and a complex resistance inheritance nature between rapeseed/canola and Sclerotinia sclerotiorum often limits the development of functional molecular markers that enable breeding for sclerotinia stem rot (SSR) resistance. However, genomics-assisted selection has the potential to accelerate the breeding for SSR resistance. Therefore, genome-wide association (GWA) mapping and genomic prediction (GP) were performed using a diverse panel of 337 rapeseed/canola genotypes. Three-week-old seedlings were screened using the petiole inoculation technique (PIT). Days to wilt (DW) up to 2 weeks and lesion phenotypes (LP) at 3, 4, and 7 days post-inoculation (dpi) were recorded. A strong correlation (r = - 0.90) between DW and LP_4dpi implied that a single time point scoring at four days could be used as a proxy trait. GWA analyses using single-locus (SL) and multi-locus (ML) models identified a total of 41, and 208 significantly associated SNPs, respectively. Out of these, ninety-eight SNPs were identified by a combination of the SL model and any of the ML models, at least two ML models, or two traits. These SNPs explained 1.25-12.22% of the phenotypic variance and considered as significant, could be associated with SSR resistance. Eighty-three candidate genes with a function in disease resistance were associated with the significant SNPs. Six GP models resulted in moderate to high (0.42-0.67) predictive ability depending on SSR resistance traits. The resistant genotypes and significant SNPs will serve as valuable resources for future SSR resistance breeding. Our results also highlight the potential of genomic selection to improve rapeseed/canola breeding for SSR resistance.

Highly Efficient Capture and Quantification of the Airborne Fungal Pathogen Sclerotinia sclerotiorum Employing a Nanoelectrode-Activated Microwell Array

In this study, we present a microdevice for the capture and quantification of Sclerotinia sclerotiorum spores, pathogenic agents of one of the most harmful infectious diseases of crops, Sclerotinia stem rot. The early prognosis of an outbreak is critical to avoid severe economic losses and can be achieved by the detection of a small number of airborne spores. However, the current lack of simple and effective methods to quantify fungal airborne pathogens has hindered the development of an accurate early warning system. We developed a device that remedies these limitations based on a microfluidic design that contains a nanothick aluminum electrode structure integrated with a picoliter well array for dielectrophoresis-driven capture of spores and on-chip quantitative detection employing impedimetric sensing. Based on experimental results, we demonstrated a highly efficient spore trapping rate of more than 90% with an effective impedimetric sensing method that allowed the spore quantification of each column in the array and achieved a sensitivity of 2%/spore at 5 kHz and 1.6%/spore at 20 kHz, enabling single spore detection. We envision that our device will contribute to the development of a low-cost microfluidic platform that could be integrated into an infectious plant disease forecasting tool for crop protection.

Efficient production of valinomycin by the soil bacterium, Streptomyces sp. ZJUT-IFE-354

A novel strain with antifungal activity against Sclerotinia sclerotiorum was isolated from soil, and identified as Streptomyces sp. ZJUT-IFE-354 using morphological and 16S rDNA sequence analysis. The bioactive metabolite produced by strain ZJUT-IFE-354 was identified and characterized as valinomycin by spectroscopic and chemical methods. The yield of valinomycin was 191.26 mg/L from the culture of Streptomyces sp. ZJUT-IFE-354, which was the highest yield to our knowledge. The in vitro antifungal activity of valinomycin against S. sclerotiorum was investigated as 0.056 ± 0.012 (EC₅₀) and 0.121 ± 0.023 μg/mL (EC₉₅), respectively, which was approximately 10.696- and 30.960-fold more active than that of carbendazim. The results from scanning electron microscopy, cell membrane permeability, and _D-sorbitol and ergosterol assay indicated that valinomycin exerted the antifungal activity probably by increasing permeability of fungal cell membrane, leading to mycelial electrolyte leakage, and eventually resulting in the death of S. sclerotiorum. Thus, valinomycin may be a promising antifungal agent to control S. sclerotiorum.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-03055-5.

Genome-wide association mapping and genomic prediction for adult stage sclerotinia stem rot resistance in Brassica napus (L) under field environments

Sclerotinia stem rot (SSR) is a fungal disease of rapeseed/canola that causes significant seed yield losses and reduces its oil content and quality. In the present study, the reaction of 187 diverse canola genotypes to SSR was characterized at full flowering stage using the agar plug to stem inoculation method in four environments. Genome-wide association study (GWAS) using three different algorithms identified 133 significant SNPs corresponding with 123 loci for disease traits like stem lesion length (LL), lesion width (LW), and plant mortality at 14 (PM_14D) and 21 (PM_21D) days. The explained phenotypic variation of these SNPs ranged from 3.6 to 12.1%. Nineteen significant SNPs were detected in two or more environments, disease traits with at least two GWAS algorithms. The strong correlations observed between LL and other three disease traits evaluated, suggest they could be used as proxies for SSR resistance phenotyping. Sixty-nine candidate genes associated with disease resistance mechanisms were identified. Genomic prediction (GP) analysis with all the four traits employing genome-wide markers resulted in 0.41-0.64 predictive ability depending on the model specifications. The highest predictive ability for PM_21D with three models was about 0.64. From our study, the identified resistant genotypes and stable significant SNP markers will serve as a valuable resource for future SSR resistance breeding. Our study also suggests that genomic selection holds promise for accelerating canola breeding progress by enabling breeders to select SSR resistance genotypes at the early stage by reducing the need to phenotype large numbers of genotypes.

First characterization of a newly emerging phytopathogen, Sclerotinia sclerotiorum causing white mold in pea

Pea (Pisum sativum L.) is of global importance as a food crop for its edible pod and seed. A new disease causing the tan to light brown blighted stems and pods has occurred in pea (P. sativum L.) plants in Chapainawabganj district, Bangladesh. A fungus with white-appressed mycelia and large sclerotia was consistently isolated from symptomatic tissues. The fungus formed funnel-shaped apothecia with sac-like ascus and endogenously formed ascospores. Healthy pea plants inoculated with the fungus produced typical white mold symptoms. The internal transcribed spacer sequences of the fungus were 100% similar to Sclerotinia sclerotiorum, considering the fungus to be the causative agent of white mold disease in pea, which was the first record in Bangladesh. Mycelial growth and sclerotial development of S. sclerotiorum were favored at 20°C and pH 5.0. Glucose was the best carbon source to support hyphal growth and sclerotia formation. Bavistin and Amistar Top inhibited the radial growth of the fungus completely at the lowest concentration. In planta, foliar application of Amistar Top showed the considerable potential to control the disease at 1.0% concentration until 7 days after spraying, while Bavistin prevented infection significantly until 15 days after spraying. A large majority (70.93%) of genotypes, including tested released pea cultivars, were susceptible, while six genotypes (6.98%) appeared resistant to the disease. These results on identification, characterization, host resistance, and fungicidal control of white mold could be valuable to achieve improved management of a new disease problem for pea cultivation.

fIdentification of B. napus small RNAs responsive to infection by a necrotrophic pathogen

BACKGROUND

Small RNAs are short non-coding RNAs that are key gene regulators controlling various biological processes in eukaryotes. Plants may regulate discrete sets of sRNAs in response to pathogen attack. Sclerotinia sclerotiorum is an economically important pathogen affecting hundreds of plant species, including the economically important oilseed B. napus. However, there are limited studies on how regulation of sRNAs occurs in the S. sclerotiorum and B. napus pathosystem.

RESULTS

We identified different classes of sRNAs from B. napus using high throughput sequencing of replicated mock and infected samples at 24 h post-inoculation (HPI). Overall, 3999 sRNA loci were highly expressed, of which 730 were significantly upregulated during infection. These 730 up-regulated sRNAs targeted 64 genes, including disease resistance proteins and transcriptional regulators. A total of 73 conserved miRNA families were identified in our dataset. Degradome sequencing identified 2124 cleaved mRNA products from these miRNAs from combined mock and infected samples. Among these, 50 genes were specific to infection. Altogether, 20 conserved miRNAs were differentially expressed and 8 transcripts were cleaved by the differentially expressed miRNAs miR159, miR5139, and miR390, suggesting they may have a role in the S. sclerotiorum response. A miR1885-triggered disease resistance gene-derived secondary sRNA locus was also identified and verified with degradome sequencing. We also found further evidence for silencing of a plant immunity related ethylene response factor gene by a novel sRNA using 5'-RACE and RT-qPCR.

CONCLUSIONS

The findings in this study expand the framework for understanding the molecular mechanisms of the S. sclerotiorum and B. napus pathosystem at the sRNA level.

Silicon Alleviates the Disease Severity of Sclerotinia Stem Rot in Rapeseed

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a devastating disease in rapeseed. The objective of this study was to investigate the role and the mechanism of silicon (Si) in alleviating the disease severity of S. sclerotiorum in rapeseed. In the absorption assays, the rapeseed that absorbed 10 mM of K₂SiO₃ exhibited an 86% decrease in lesion size on infected leaves as compared with controls. In the spray assay, the lesion length on rapeseed stems was reduced by 30.5-32.9% with the use of 100 mM of a foliar Si fertilizer as compared with controls. In the pot assay, the lesion length on rapeseed stems was reduced by 34.9-38.3% when using the Si fertilizer as basal fertilizer. In the field assay, both the disease incidence and disease index of sclerotinia stem rot were significantly reduced with the usage of a solid Si fertilizer, Si foliar fertilizer, and the application of both, without negative affection on the main agronomic traits and seed quality of rapeseed. The transcriptome sequencing, quantitative reverse transcription PCR (qRT-PCR), and biochemical assays between K₂SO₄- and K₂SiO₃- treated rapeseed leaves revealed that Si promoted the biosynthesis of defense-related substances and enhanced the antioxidation and detoxification abilities of rapeseed after infection. Thus, this study concluded that Si can alleviate the disease severity of S. sclerotiorum in rapeseeds, partially due to the induced defense responses.

Genome Mining and Evaluation of the Biocontrol Potential of Pseudomonas fluorescens BRZ63, a New Endophyte of Oilseed Rape (Brassica napus L.) against Fungal Pathogens

Endophytic bacteria hold tremendous potential for use as biocontrol agents. Our study aimed to investigate the biocontrol activity of Pseudomonas fluorescens BRZ63, a new endophyte of oilseed rape (Brassica napus L.) against Rhizoctonia solani W70, Colletotrichum dematium K, Sclerotinia sclerotiorum K2291, and Fusarium avenaceum. In addition, features crucial for biocontrol, plant growth promotion, and colonization were assessed and linked with the genome sequences. The in vitro tests showed that BRZ63 significantly inhibited the mycelium growth of all tested pathogens and stimulated germination and growth of oilseed rape seedlings treated with fungal pathogens. The BRZ63 strain can benefit plants by producing biosurfactants, siderophores, indole-3-acetic acid (IAA), 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and ammonia as well as phosphate solubilization. The abilities of exopolysaccharide production, autoaggregation, and biofilm formation additionally underline its potential to plant colonization and hence biocontrol. The effective colonization properties of the BRZ63 strain were confirmed by microscopy observations of EGFP-expressing cells colonizing the root surface and epidermal cells of Arabidopsis thaliana Col-0. Genome mining identified many genes related to the biocontrol process, such as transporters, siderophores, and other secondary metabolites. All analyses revealed that the BRZ63 strain is an excellent endophytic candidate for biocontrol of various plant pathogens and plant growth promotion.

Single ascospore detection for the forecasting of Sclerotinia stem rot of canola

Smart-agriculture technologies comprise a set of management systems designed to sustainably increase the efficiency and productivity of farming. In this paper, we present a lab-on-a-chip device that can be employed as a plant disease forecasting tool for canola crop. Our device can be employed as a platform to forecast potential outbreaks of one of the most devastating diseases of canola and other crops, Sclerotinia stem rot. The system consists of a microfluidic chip capable of detecting single airborne Sclerotinia sclerotiorum ascospores. Target ascospores are injected into the chip and selectively captured by dielectrophoresis, while other spores in the sample are flushed away. Afterward, captured ascospores are released into the flow stream of the channel and are detected employing electrochemical impedance spectroscopy and coplanar microelectrodes. Our device provides a design for a low-cost, miniaturized, and automated platform technology for airborne spore detection and disease prevention.

Effect of Wetness Duration and Incubation Temperature on Development of Ascosporic Infections by Sclerotinia sclerotiorum

The impact of wetness duration and incubation temperatures on Sclerotinia sclerotiorum ascospore germination and ascosporic infection efficiency were evaluated. Ascospore germination was optimal when incubated in continuous moisture (free water) at 21°C. Significantly lower germination was observed at 10 or 30°C. Interrupting ascospore wet incubation was detrimental for germination. In infection efficiency studies, dry bean and canola flowers were inoculated with dry ascospores and placed on leaves of dry bean and canola plants, respectively. Dry bean plants were incubated for 196 h at 18 to 20°C in alternating 8 to 16 h wet/12 to 24 h dry periods. Canola plants were incubated for 240 h at 10, 15, 20, 25, or 30°C in alternating 6 to 18 h wet/18 to 6 h dry periods. Interrupting wet incubation delayed symptom appearance and hindered development of the epidemics on both plant types. Logistic regression models estimated at 50% the probability of disease development on dry bean and canola plants when 68 and 48 h of wet incubation at 20°C accumulated in a period of 6 days, respectively. The canola model was validated using data from field trials. Results of these studies will contribute to develop more accurate warning models for diseases caused by S. sclerotiorum.

Pseudomonas synxantha 2-79 Transformed with Pyrrolnitrin Biosynthesis Genes Has Improved Biocontrol Activity Against Soilborne Pathogens of Wheat and Canola

A four-gene operon (prnABCD) from Pseudomonas protegens Pf-5 encoding the biosynthesis of the antibiotic pyrronitrin was introduced into P. synxantha (formerly P. fluorescens) 2-79, an aggressive root colonizer of both dryland and irrigated wheat roots that naturally produces the antibiotic phenazine-1-carboxylic acid and suppresses both take-all and Rhizoctonia root rot of wheat. Recombinant strains ZHW15 and ZHW25 produced both antibiotics and maintained population sizes in the rhizosphere of wheat that were comparable to those of strain 2-79. The recombinant strains inhibited in vitro the wheat pathogens Rhizoctonia solani anastomosis group 8 (AG-8) and AG-2-1, Gaeumannomyces graminis var. tritici, Sclerotinia sclerotiorum, Fusarium culmorum, and F. pseudograminearum significantly more than did strain 2-79. Both the wild-type and recombinant strains were equally inhibitory of Pythium ultimum. When applied as a seed treatment, the recombinant strains suppressed take-all, Rhizoctonia root rot of wheat, and Rhizoctonia root and stem rot of canola significantly better than did wild-type strain 2-79.

Real-Time Quantitative and Ion-Metal Indicator LAMP-Based Assays for Rapid Detection of Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is one of the most devastating and cosmopolitan plant pathogens. Rapid detection of S. sclerotiorum can provide growers an advantage in knowing what control measures should be taken to minimize crop damage and financial losses caused by it. Loop-mediated isothermal amplification (LAMP) is a fast, sensitive, and specific nucleic acid amplification method that does not require a thermal cycler. This study aimed to develop a LAMP-based assay for the specific detection of S. sclerotiorum (Ss-LAMP). A real-time quantitative LAMP reaction (Ss-qLAMP) and a calcein ion indicator-based LAMP reaction (Ss-cLAMP) were designed, optimized, and tested on fungi, plant, and soil samples. The Ss-LAMP reactions were very specific and sensitive. Applying the artificially inoculated soil samples with DNA purified by five protocols in the Ss-qLAMP reaction, it was possible to detect and quantify the pathogen DNA, regardless of the extraction protocol. Naturally infected soybean tissues had the pathogen detected by Ss-cLAMP directly in the reaction tube with no DNA extraction requirement. The assays should be applicable for many types of samples, such as soil, spore traps, and plant tissues from several crops, with no requirement for DNA extraction. The Ss-LAMP reactions took less than 1 h to complete, and they can be made directly in the field with real-time quantitative results (Ss-qLAMP) or qualitative naked-eye visual results (Ss-cLAMP). Results were obtained with 10 pg of DNA or 10 ng of crude mycelium, suggesting a detection limit close to a single DNA copy. Ss-LAMP reactions will allow rapid and accurate diagnosis of S. sclerotiorum and assist in pathogen management and control.

Introgression and pyramiding of genetic loci from wild Brassica oleracea into B. napus for improving Sclerotinia resistance of rapeseed

Resistant rapeseed lines pyramided with multiple resistant QTLs derived from Brassica oleracea were developed via a hexaploidy strategy. Rapeseed (Brassica napus L.) suffers heavily from Sclerotinia stem rot, but the breeding of Sclerotinia-resistant rapeseed cultivar has been unsuccessful. During the study, interspecific hexaploids were generated between rapeseed variety 'Zhongshuang 9' and a wild B. oleracea which was highly resistant to S. sclerotiorum, followed by backcrossing with Zhongshuang 9 and successive selfing. By molecular marker-assisted selection, three major resistant QTLs were transferred and pyramided from B. oleracea into two BC1F8 lines which exhibited ~ 35% higher resistance level than Zhongshuang 9 and produced good seed yield and seed quality. It is the first report on successful development of Sclerotinia-resistant rapeseed lines by introducing multiple resistant loci from wild B. oleracea. This study revealed the effectiveness of pyramiding multiple QTLs in improving Sclerotinia resistance in rapeseed and provided a novel breeding strategy on utilization of B. oleracea in rapeseed improvement.

Transcriptome analysis of the plant pathogen Sclerotinia sclerotiorum interaction with resistant and susceptible canola (Brassica napus) lines

Sclerotinia stem rot is an economically important disease of canola (Brassica napus) and is caused by the fungal pathogen Sclerotinia sclerotiorum. This study evaluated the differential gene expression patterns of S. sclerotiorum during disease development on two canola lines differing in susceptibility to this pathogen. Sequencing of the mRNA libraries derived from inoculated petioles and mycelium grown on liquid medium generated approximately 164 million Illumina reads, including 95 million 75-bp-single reads, and 69 million 50-bp-paired end reads. Overall, 36% of the quality filter-passed reads were mapped to the S. sclerotiorum reference genome. On the susceptible line, 1301 and 1214 S. sclerotiorum genes were differentially expressed at early (8-16 hours post inoculation (hpi)) and late (24-48 hpi) infection stages, respectively, while on the resistant line, 1311 and 1335 genes were differentially expressed at these stages, respectively. Gene ontology (GO) categories associated with cell wall degradation, detoxification of host metabolites, peroxisome related activities like fatty acid ß-oxidation, glyoxylate cycle, oxidoreductase activity were significantly enriched in the up-regulated gene sets on both susceptible and resistant lines. Quantitative RT-PCR of six selected DEGs further validated the RNA-seq differential gene expression analysis. The regulation of effector genes involved in host defense suppression or evasion during the early infection stage, and the expression of effectors involved in host cell death in the late stage of infection provide supporting evidence for a two-phase infection model involving a brief biotrophic phase during early stages of infection. The findings from this study emphasize the role of peroxisome related pathways along with cell wall degradation and detoxification of host metabolites as the key mechanisms underlying pathogenesis of S. sclerotiorum on B. napus.

Glucosinolate Profiling and Expression Analysis of Glucosinolate Biosynthesis Genes Differentiate White Mold Resistant and Susceptible Cabbage Lines

Sclerotinia stem rot (white mold), caused by the fungus Sclerotinia sclerotiorum, is a serious disease of Brassica crops worldwide. Despite considerable progress in investigating plant defense mechanisms against this pathogen, which have revealed the involvement of glucosinolates, the host⁻pathogen interaction between cabbage (Brassica oleracea) and S. sclerotiorum has not been fully explored. Here, we investigated glucosinolate profiles and the expression of glucosinolate biosynthesis genes in white-mold-resistant (R) and -susceptible (S) lines of cabbage after infection with S. sclerotiorum. The simultaneous rise in the levels of the aliphatic glucosinate glucoiberverin (GIV) and the indolic glucosinate glucobrassicin (GBS) was linked to white mold resistance in cabbage. Principal component analysis showed close association between fungal treatment and cabbage GIV and GBS contents. The correlation analysis showed significant positive associations between GIV content and expression of the glucosinolate biosynthesis genes ST5b-Bol026202 and ST5c-Bol030757, and between GBS content and the expression of the glucosinolate biosynthesis genes ST5a-Bol026200 and ST5a-Bol039395. Our results revealed that S. sclerotiorum infection of cabbage induces the expression of glucosinolate biosynthesis genes, altering the content of individual glucosinolates. This relationship between the expression of glucosinolate biosynthesis genes and accumulation of the corresponding glucosinolates and resistance to white mold extends the molecular understanding of glucosinolate-negotiated defense against S. sclerotiorum in cabbage.

Immuno-impedimetric Biosensor for Onsite Monitoring of Ascospores and Forecasting of Sclerotinia Stem Rot of Canola

Sclerotinia stem rot, caused by the fungal pathogen Sclerotinia sclerotiorum, is a destructive disease of canola and many other broadleaf crops. The primary inoculum responsible for initiating Sclerotinia epidemics is airborne ascospores released from the apothecia of sclerotia. Timely detection of the presence of airborne ascospores can serve as an early-warning system for forecasting and management of the disease. A major challenge is to develop a portable and automated device which can be deployed onsite to detect and quantify the presence of minute quantities of ascospores in the air and serves as a unit in a network of systems for forecasting of the epidemic. In this communication, we present the development of an impedimetric non-Faradaic biosensor based on anti-S. sclerotiorum polyclonal antibodies as probes to selectively capture the ascospores and sense their binding by an impedance based interdigitated electrode which was found to directly and unambiguously correlate the number of ascospores on sensor surface with the impedance response.

Independently founded populations of Sclerotinia sclerotiorum from a tropical and a temperate region have similar genetic structure

Sclerotinia sclerotiorum populations from tropical agricultural zones have been suggested to be more variable compared to those from temperate zones. However, no data were available comparing populations from both zones using the same set of markers. In this study, we compared S. sclerotiorum populations from the United States of America (USA, temperate) and southeast Brazil (tropical) using the frequency of mycelial compatibility groups (MCGs) and 13 microsatellite (SSR) markers. Populations were sourced from diseased plants within leguminous crops in New York, USA (NY; n = 78 isolates), and Minas Gerais State, Brazil (MG; n = 109). Twenty MCGs were identified in NY and 14 were previously reported in MG. The effective number of genotypes based on Hill's number of order 0, which corresponded to the number of multilocus genotypes (MLGs) were 22 (95% CI = 15.6-28.4) and 24 (95% CI = 18.9-29.1) in NY and MG, respectively. Clonal fractions of MLGs were 71.8% (NY) and 78.0% (MG). The effective number of genotypes based on Hill's number of orders 1 and 2 in NY were 8.9 (95% CI = 5.2-12.6) and 4.4 (95% CI = 2.6-6.1), respectively. For MG these indices were 11.4 (95% CI = 8.7-14.1) and 7.1 (95% CI = 5.1-9.0), respectively. There were no significant differences of allelic richness, private allelic richness, gene diversity, effective number of alleles and genotype evenness between the NY and MG populations. The populations were differentiated, with 29% of total variance attributed to differences between them and G''ST and Jost's D indices higher than 0.50. Cluster analysis revealed dissimilarity higher than 80% among most MLGs from both populations. Different alleles segregated in the populations but both had similar levels of genotypic variability.

Genome Wide Identification and Functional Prediction of Long Non-Coding RNAs Responsive to Sclerotinia sclerotiorum Infection in Brassica napus

Sclerotinia stem rot caused by Sclerotinia sclerotiorum affects canola production worldwide. Emerging evidence suggests that long non-coding RNAs (lncRNAs) play important roles in the regulation of gene expression in plants, in response to both abiotic and biotic stress. So far, identification of lncRNAs has been limited to a few model plant species, and their roles in mediating responses to biotic stresses are yet to be characterized in Brassica napus. The present study reports the identification of novel lncRNAs responsive to S. sclerotiorum infection in B. napus at two time points after infection (24 hpi and 48 hpi) using a stranded RNA-Sequencing technique and a detection pipeline for lncRNAs. Of the total 3,181 lncRNA candidates, 2,821 lncRNAs were intergenic, 111 were natural antisense transcripts, 76 possessed exonic overlap with the reference coding transcripts while the remaining 173 represented novel lnc- isoforms. Forty one lncRNAs were identified as the precursors for microRNAs (miRNAs) including miR156, miR169 and miR394, with significant roles in mediating plant responses to fungal phytopathogens. A total of 931 differentially expressed lncRNAs were identified in response to S. sclerotiorum infection and the expression of 12 such lncRNAs was further validated using qRT-PCR. B. napus antisense lncRNA, TCONS_00000966, having 90% overlap with a plant defensin gene, showed significant induction at both infection stages, suggesting its involvement in the transcriptional regulation of defense responsive genes under S. sclerotiorum infection. Additionally, nine lncRNAs showed overlap with cis-regulatory regions of differentially expressed genes of B. napus. Quantitative RT-PCR verification of a set of S. sclerotiorum responsive sense/antisense transcript pairs revealed contrasting expression patterns, supporting the hypothesis that steric clashes of transcriptional machinery may lead to inactivation of sense promoter. Our findings highlight the potential contributions of lncRNAs in regulating expression of plant genes that respond to biotic stress.

Microsatellite markers used for genome-wide association mapping of partial resistance to Sclerotinia sclerotiorum in a world collection of Brassica napus

The fungal pathogen Sclerotinia sclerotiorum causes stem rot of oilseed rape (Brassica napus) worldwide. In preparation for genome-wide association mapping (GWAM) of sclerotinia resistance in B. napus, 152 accessions from diverse geographical regions were screened with a single Canadian isolate, #321. Plants were inoculated by attaching mycelium plugs to the main stem at full flower. Lesion lengths measured 7, 14 and 21 days after inoculation were used to calculate the area under the disease progress curve (AUDPC). Depth of penetration was noted and used to calculate percent soft and collapsed lesions (% s + c). The two disease traits were highly correlated (r = 0.93). Partially resistant accessions (AUDPC <7 and % s + c <2) were identified primarily from South Korea and Japan with a few from Pakistan, China and Europe. Genotyping of accessions with 84 simple sequence repeat markers provided 690 polymorphic loci for GWAM. The general linear model in TASSEL best fitted the data when adjusted for population structure (STRUCTURE), GLM + Q. After correction for positive false discovery rate, 34 loci were significantly associated with both disease traits of which 21 alleles contributed to resistance, while the remaining enhanced susceptibility. The phenotypic variation explained by the loci ranged from 6 to 25 %. Five loci mapped to published quantitative trait loci conferring sclerotinia resistance in Chinese lines.

A Quantitative PCR System for Measuring Sclerotinia sclerotiorum in Canola (Brassica napus)

Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is an economically important disease of canola (Brassica napus) commonly managed by routine application of fungicides. Petal infestation has been demonstrated to be an important stage of the disease cycle in canola and has been the focus of previously developed Sclerotinia stem rot risk assessment methods. Quantitative polymerase chain reaction (qPCR) analysis can provide a more rapid and accurate assessment of petal infestation levels. Primers and a hydrolysis probe were designed to amplify a 70-bp region of an S. sclerotiorum-specific gene, SS1G_00263. A hydrolysis probe-based qPCR assay was developed that had a detection limit of 8.0 × 10^-4 ng of S. sclerotiorum DNA and only amplified S. sclerotiorum DNA. Evaluation of petals collected at five sampling points in each of 10 commercial canola fields on each of two sampling dates (corresponding to 20 to 30% bloom and 40 to 50% bloom) revealed S. sclerotiorum DNA infestation levels of 0 to 3.3 × 10^-1 ng/petal. This qPCR assay can be used to reliably quantify petal infestation and, with further research, has the potential to serve as the basis for a Sclerotinia stem rot risk assessment tool or as a means to study Sclerotinia stem rot epidemiology.

Transfer of sclerotinia resistance from wild relative of Brassica oleracea into Brassica napus using a hexaploidy step

Sclerotinia resistance was transferred into rapeseed from a wild relative of Brassica oleracea (B. incana) using hexaploids derived from crosses between B. incana and rapeseed as a bridge. A high level of resistance against Sclerotinia sclerotiorum has been documented in wild Brassica oleracea, but not in cultivated rapeseed (Brassica napus). To transfer sclerotinia resistance from a wild relative into rapeseed, a strategy was proposed using hexaploids (AACCCC) derived from crosses between the wild B. oleracea-related B. incana genotype 'C01' and the Chinese rapeseed variety 'Zhongshuang 9' as a bridge. Progenies (BC1F1) generated by backcrossing the hexaploid to 'Zhongshuang 9' could be generated with a high crossability (average 18.3 seeds per pod). Seventy-three individuals in BC1F1 were firstly screened for resistance with five molecular markers linked to the major resistance QTL on chromosome C09 in 'C01', and 11 individuals harboring resistance loci were selected to develop vegetative clones. Of these, five exhibited significantly higher resistance than 'Zhongshuang 9' and the most resistant individual was chosen to develop the BC1F2 progeny. Finally, five individual genotypes with nearly twofold higher resistance than 'Zhongshuang 9' were found among 100 BC1F2 individuals by using marker-assisted selection and resistance evaluation. Hereof, one rapeseed-type individual with 38 chromosomes and good self-fertility (15.0 ± 3.56 seeds/pod) was identified. Our results indicate that the proposed strategy is effective for transferring sclerotinia resistance from a wild relative of B. oleracea into rapeseed.

Identification of genomic regions involved in resistance against Sclerotinia sclerotiorum from wild Brassica oleracea

The lack of resistant source has greatly restrained resistance breeding of rapeseed (Brassica napus, AACC) against Sclerotinia sclerotiorum which causes severe yield losses in rapeseed production all over the world. Recently, several wild Brassica oleracea accessions (CC) with high level of resistance have been identified (Mei et al. in Euphytica 177:393-400, 2011), bringing a new hope to improve Sclerotinia resistance of rapeseed. To map quantitative trait loci (QTL) for Sclerotinia resistance from wild B. oleracea, an F2 population consisting of 149 genotypes, with several clones of each genotypes, was developed from one F1 individual derived from the cross between a resistant accession of wild B. oleracea (B. incana) and a susceptible accession of cultivated B. oleracea var. alboglabra. The F2 population was evaluated for Sclerotinia reaction in 2009 and 2010 under controlled condition. Significant differences among genotypes and high heritability for leaf and stem reaction indicated that genetic components accounted for a large portion of the phenotypic variance. A total of 12 QTL for leaf resistance and six QTL for stem resistance were identified in 2 years, each explaining 2.2-28.4 % of the phenotypic variation. The combined effect of alleles from wild B. oleracea reduced the relative susceptibility by 22.5 % in leaves and 15 % in stems on average over 2 years. A 12.8-cM genetic region on chromosome C09 of B. oleracea consisting of two major QTL intervals for both leaf and stem resistance was assigned into a 2.7-Mb genomic region on chromosome A09 of B. rapa, harboring about 30 putative resistance-related genes. Significant negative corrections were found between flowering time and relative susceptibility of leaf and stem. The association of flowering time with Sclerotinia resistance is discussed.

Effect of Sclerotial Water Content on Carpogenic Germination of Sclerotinia sclerotiorum

The relationship between moisture content and carpogenic germination (CG) of Sclerotinia sclerotiorum sclerotia and the dynamics of sclerotial water imbibition were studied in a controlled environment. The study was conducted using laboratory-produced sclerotia from seven S. sclerotiorum isolates. The quantity and rate of water imbibition by three sizes of sclerotia was determined gravimetrically in silty clay, sandy loam, and sandy soils maintained at 100, 75, 50, and 25% of soil saturation and in distilled water. Smaller sclerotia imbibed water at a significantly faster rate (P = 0.05) than larger sclerotia in water and in soil at all saturation percentages. When buried in soil, small, medium, and large sclerotia were fully saturated within 5, 15, and 25 h, respectively, in all three soil types and moisture percentages. The effect of sclerotia moisture content on CG was evaluated on sclerotia maintained at 95 to 100, 70 to 80, 40 to 50, and 20 to 30% of their water saturation capacity using cool mist humidifiers. Sclerotial moisture content significantly influenced CG (P = 0.05). Maximum CG was observed on fully saturated sclerotia, while no CG was observed below 70 to 80% of saturation. These findings help explain S. sclerotiorum's ability to produce apothecia in soils with relatively low moisture levels.

Effect of Sclerotinia sclerotiorum on the disease development, growth, oil yield and biochemical changes in plants of Mentha arvensis

Experiment was carried out to determine the effect of Sclerotinia sclerotiorum on the disease development, growth, oil yield and biochemical changes in the plants of Mentha arvensis. With the increase in initial inoculum levels of S. sclerotiorum a corresponding decrease in plant fresh and dry weights were recorded. The maximum reduction in the shoot-roots/suckers fresh weight and shoot-roots/suckers dry weights (39.8%, 43.6%, 40.3% and 42.9%), respectively, was observed at the highest initial inoculum level of 12 g fungal mycelium/5 kg soil as compared to uninoculated control. The infection of roots and suckers due to S. sclerotiorum increased with increasing initial inoculum levels. At the lowest initial inoculum (1.0 g mycelium/5 kg soil), infection was observed 18.0% and at the highest (12 g mycelium/5 kg soil), it was 80.2%. Significant (P ⩽ 0.01) reduction in oil yield, total chlorophyll, total phenol and total sugar content of M. arvensis plants was observed at the lowest inoculum level as compared to uninoculated control.

Detection of Sclerotinia sclerotiorum using a monomeric and dimeric single-chain fragment variable (scFv) antibody

Sclerotinia sclerotiorum (Lib.) de Bary is a phytopathogenic fungus capable of causing significant yield losses in numerous crops, including canola, in which the fungus causes sclerotinia stem rot. Immunological detection methods to rapidly determine the presence of S. sclerotiorum on plants may provide growers with a viable diagnostic tool to aid with fungicide use decisions. This paper discusses the generation of a monomeric and dimeric single-chain, variable fragment (scFv) antibody with affinity for S. sclerotiorum using phage display technology. The bacterially expressed and purified scFv is shown to bind S. sclerotiorum with some cross-reactivity with the closely related phytopathogen Botrytis cinerea (Pers.:Fr.). The dimeric scFv displayed improved binding to the fungus as compared to the monomer and could detect the presence of mycelia in inoculated canola petals. To the authors' knowledge, this is the first report of a scFv dimer with affinity for S. sclerotiorum that has the potential for use in the development of a new diagnostic test.

Proteome changes in leaves of Brassica napus L. as a result of Sclerotinia sclerotiorum challenge

Sclerotinia stem rot, caused by the necrotrophic fungal pathogen Sclerotinia sclerotiorum, is a serious disease of canola (Brassica napus L.). To increase the understanding of the B. napus- S. sclerotiorum interaction, proteins potentially involved in mediating this interaction were identified and characterized. Upon infection of canola leaves by S. sclerotiorum, necrosis of host leaves was observed by 12 h and rapidly progressed during the later time points. These morphological observations were supported by microscopic study performed at different time points after pathogen challenge. Leaf proteins were extracted and analyzed by 2-DE, which revealed the modulation of 32 proteins (12 down- and 20 up-regulated). The identities of these proteins were established by ESI-q-TOF MS/MS and included proteins involved in photosynthesis and metabolic pathways, protein folding and modifications, hormone signaling, and antioxidant defense. Gene expression analysis of selected genes was performed by qRT-PCR, whereas the elevated levels of the antioxidant enzymes peroxidase and superoxide dismutase were validated by enzyme assays. To the authors' best knowledge, this is the first proteomics-based investigation of B. napus-S. sclerotiorum interaction, and the roles of many of the proteins identified are discussed within the context of this pathosystem.