A protocol for increased throughput phenotyping of plant resistance to the pollen beetle

BACKGROUND

Improving crop resistance to insect herbivores is a major research objective in breeding programs. Although genomic technologies have increased the speed at which large populations can be genotyped, breeding programs still suffer from phenotyping constraints. The pollen beetle (Brassicogethes aeneus) is a major pest of oilseed rape for which no resistant cultivar is available to date, but previous studies have highlighted the potential of white mustard as a source of resistance and introgression of this resistance appears to be a promising strategy. Here we present a phenotyping protocol allowing mid-throughput (i.e., increased throughput compared to current methods) acquisition of resistance data, which could then be used for genetic mapping of QTLs.

RESULTS

Contrasted white mustard genotypes were selected from an initial field screening and then evaluated for their resistance under controlled conditions using a standard phenotyping method on entire plants. We then upgraded this protocol for mid-throughput phenotyping, by testing two alternative methods. We found that phenotyping on detached buds did not provide the same resistance contrasts as observed with the standard protocol, in contrast to the phenotyping protocol with miniaturized plants. This protocol was then tested on a large panel composed of hundreds of plants. A significant variation in resistance among genotypes was observed, which validates the large-scale application of this new phenotyping protocol.

CONCLUSION

The combination of this mid-throughput phenotyping protocol and white mustard as a source of resistance against the pollen beetle offers a promising avenue for breeding programs aiming to improve oilseed rape resistance. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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 Leptosphaeria maculans increases importance of L. biglobosa as a cause of phoma stem canker epidemics on oilseed rape

BACKGROUND

Phoma stem canker is a damaging disease of oilseed rape caused by two related fungal species, Leptosphaeria maculans and L. biglobosa. However, previous work has mainly focused on L. maculans and there has been little work on L. biglobosa. This work provides evidence of the importance of L. biglobosa to stem canker epidemics in the UK.

RESULTS

Quantification of L. maculans and L. biglobosa DNA using species-specific quantitative PCR showed that L. biglobosa caused both upper stem lesions and stem base cankers on nine oilseed rape cultivars in the UK. Upper stem lesions were mainly caused by L. biglobosa. For stem base cankers, there was more L. maculans DNA than L. biglobosa DNA in the susceptible cultivar Drakkar, while there was more L. biglobosa DNA than L. maculans DNA in cultivars with the resistance gene Rlm7 against L. maculans. The frequency of L. biglobosa detected in stem base cankers increased from 14% in 2000 to 95% in 2013. Ascospores of L. biglobosa and L. maculans were mostly released on the same days and the number of L. biglobosa ascospores in air samples increased from the 2010/2011 to 2012/2013 growing seasons.

CONCLUSION

Effective control of L. maculans increased infection by L. biglobosa, causing severe upper stem lesions and stem base cankers, leading to yield losses. The importance of L. biglobosa to phoma stem canker epidemics can no longer be ignored. Effective control of phoma stem canker epidemics needs to target both L. maculans and L. biglobosa. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Endophytic Bacillus vallismortis and Bacillus tequilensis bacteria isolated from medicinal plants enhance phosphorus acquisition and fortify Brassica napus L. vegetative growth and metabolic content

Phosphorus fertilization imposes critical limitations on crop productivity and soil health. The aim of the present work is to explore the potential of two phosphate solubilizing bacteria (PSB) species in phosphorus supplementation of canola (Brassica napus L.). Out of 38 bacterial isolates obtained from nine medicinal plants, two bacterial strains (20P and 28P) were proved as the most potent for the in-vitro tricalcium phosphate solubilization test. These isolates verified their activity toward different enzymes as nitrogenase and alkaline phosphatase. Also, 20P and 28P gave a high amount of indole-3-acetic acid, 34.16 μg/ml and 35.20 μg/ml, respectively, and were positive for siderophores production as they detected moderate affinity for iron chelation. Molecular identification confirmed that strain 20P was Bacillus vallismortis and strain 28P was Bacillus tequilensis. A pot experiment was conducted to study the effect of four different phosphorus concentrations (0%, 50%, 75%, and 100% P) each alone and/or in combination with B. vallismortis, B. tequilensis, or both bacterial isolates on the vegetative growth and some physiological parameters of canola. The combined treatment of 50% phosphorus + (B. vallismortis + B. tequilensis) was generally the most effective with respect to shoot height, shoot dry mass, leaf area, photosynthetic pigment fractions, total sugar content, and accumulated NPK content. In contrast, the rhizosphere pH reached the minimum value under the same treatment. These findings highlighted the potential use of PSB (B. vallismortis and B. tequilensis) along with phosphorus fertilization as a safe sustainable tactic.

A CRISPR/Cas9-based vector system enables the fast breeding of selection-marker-free canola with Rcr1-rendered clubroot resistance

Breeding for disease resistance in major crops is of crucial importance for global food security and sustainability. However, common biotechnologies such as traditional transgenesis or genome editing do not provide an ideal solution, whereas transgenic crops free of selection markers such as cisgenic/intragenic crops might be suitable. In this study, after cloning and functional verification of the Rcr1 gene for resistance to clubroot (Plasmodiophora brassicae), we confirmed that the genes Rcr1, Rcr2, Rcr4, and CRa from Brassica rapa crops and the resistance gene from B. napus oilseed rape cv. 'Mendel' on chromosome A03 were identical in their coding regions. We also determined that Rcr1 has a wide distribution in Brassica breeding materials and renders potent resistance against multiple representative clubroot strains in Canada. We then modified a CRISPR/Cas9-based cisgenic vector system and found that it enabled the fast breeding of selection-marker-free transgenic crops with add-on traits, with selection-marker-free canola (B. napus) germplasms with Rcr1-rendered stable resistance to clubroot disease being successfully developed within 2 years. In the B. napus background, the intragenic vector system was able to remove unwanted residue sequences from the final product with high editing efficiency, and off-target mutations were not detected. Our study demonstrates the potential of applying this breeding strategy to other crops that can be transformed by Agrobacterium. Following the streamlined working procedure, intragenic germplasms can be developed within two generations, which could significantly reduce the breeding time and labor compared to traditional introgression whilst still achieving comparable or even better breeding results.

The effects of insecticide seed treatments on the parasitism and predation of Myzus persicae (Homoptera: Aphididae) in canola

The green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), is a major pest of brassica plants, with the ability to transmit > 100 viruses. Although the adoption of Integrated Pest Management is increasing, chemical treatment remains the predominant method used to control M. persicae globally. Insecticide seed treatments, typically with neonicotinoid active ingredients, have become commonplace in canola crops, and are viewed as a "softer" alternative to foliar sprays but may nevertheless impact natural enemies of M. persicae. In this study, the effects of canola seed treatments, containing imidacloprid, thiamethoxam, and a mixture of thiamethoxam + lambda-cyhalothrin, were investigated on the parasitoid wasp, Aphidius colemani Viereck (Hymenoptera: Braconidae) and the green lacewing, Mallada signatus (Schneider) (Neuroptera: Chrysopidae), both important natural enemies of M. persicae. Laboratory trials were undertaken using whole plants, with lethal and sublethal effects assessed by measuring several traits. Compared with untreated plants, more aphid mummies were produced and more A. colemani were reared on plants treated with thiamethoxam + lambda-cyhalothrin and more aphid mummies were produced on imidacloprid plants. Imidacloprid reduced the time A. colemani spent searching for M. persicae and thiamethoxam reduced its cleaning time. However, after A. colemani were removed from treated plants, there were no such effects observed, suggesting these impacts were relatively short-lived. We found no significant effects of seed treatments on M. signatus. These results point to the complexity of ecotoxicology studies involving multiple trophic levels and indicate that seed treatments may have variable impacts on key fitness traits of natural enemies.

Influence of Grazing on Canola Grain, Canola Forage Yield, and Beef Cattle Performance

Interest is increasing in grazing winter canola (Brassica napus) as an alternative crop in winter wheat (Triticum aestivum) rotations in the Southern High Plains (SHP) of the USA and similar environments. In this stidy, winter cereal rye (Secale cereale) and winter canola pastures (forage) were compared for two winter growing seasons at New Mexico State University's Rex E. Kirksey Agricultural Science Center at Tucumcari, NM, USA, to determine the relative effect of pasture type on late-gestation beef cows and growing yearling cattle, along with the effect of grazing on canola grain production. Canola grain yields were reduced by 25% when canola was grazed until removal approximately one month after grazing was initiated, but before the onset of rapid regrowth after winter (641 vs. 486 kg grain ha-1 for never grazed or grazed canola, respectively, p < 0.0256). No differences existed for forage mass, nutritive value, or animal performance, although forage mineral composition of canola could be a concern. Grazing winter canola as a dual-purpose crop in the SHP and similar environments is feasible when proper grazing management is applied; producers should anticipate a 20-25% reduction in grain yield, but expect animal gains to offset that loss.

Plant growth-promoting rhizobacteria: Peribacillus frigoritolerans 2RO30 and Pseudomonas sivasensis 2RO45 for their effect on canola growth under controlled as well as natural conditions

Even though canola is one of the most important industrial crops worldwide, it has high nutrient requirements and is susceptible to pests and diseases. Therefore, natural methods are sought to support the development of these plants. One of those methods could be a plant growth-promoting rhizobacteria (PGPR) that have a beneficial effect on plant development. The aim of this study was a genomic comparison of two PGPR strains chosen based on their effect on canola growth: Peribacillus frigoritolerans 2RO30, which stimulated canola growth only in sterile conditions, and Pseudomonas sivasensis 2RO45, which promoted canola growth in both sterile and non-sterile conditions. First of all, six bacterial strains: RO33 (Pseudomonas sp.), RO37 (Pseudomonas poae), RO45 (Pseudomonas kairouanensis), 2RO30 (Peribacillus frigoritolerans), 2RO45 (Pseudomonas sivasensis), and 3RO30 (Pseudomonas migulae), demonstrating best PGP traits in vitro, were studied for their stimulating effect on canola growth under sterile conditions. P. frigoritolerans 2RO30 and P. sivasensis 2RO45 showed the best promoting effect, significantly improving chlorophyll content index (CCI) and roots length compared to the non-inoculated control and to other inoculated seedlings. Under non-sterile conditions, only P. sivasensis 2RO45 promoted the canola growth, significantly increasing CCI compared to the untreated control and to other inoculants. Genome comparison revealed that the genome of P. sivasensis 2RO45 was enriched with additional genes responsible for ACC deaminase (acdA), IAA (trpF, trpG), and siderophores production (fbpA, mbtH, and acrB) compared to 2RO30. Moreover, P. sivasensis 2RO45 showed antifungal effect against all the tested phytopathogens and harbored six more biosynthetic gene clusters (BGC), namely, syringomycin, pyoverdin, viscosin, arylpolyene, lankacidin C, and enterobactin, than P. frigoritolerans 2RO30. These BGCs are well known as antifungal agents; therefore, it can be assumed that these BGCs were responsible for the antifungal activity of P. sivasensis 2RO45 against all plant pathogens. This study is the first report describing P. sivasensis 2RO45 as a canola growth promoter, both under controlled and natural conditions, thus suggesting its application in improving canola yield, by improving nutrient availability, enhancing stress tolerance, and reducing environmental impact of farming practices.

First report of Xanthomonas campestris pv. campestris causing black rot on oilseed rape (Brassica napus L.) in France

In October 2022, v-shaped necrotic lesions were observed on the leaf margins of field-grown winter oilseed rape (WOSR), Brassica napus L., in western France (Ille-et-Vilaine (35) and Maine-et-Loire (49) departments). Disease incidence on volunteers and cultivated WOSR was generally low (5-10 %) but occasionally up to 80% on some fields. Leaf sections sampled from the margin of necrotic leaf tissue were dilacerated in sterile deionized water and the extract was spread onto tryptone soya agar (TSA) with cycloheximide (100 mg.L-1) and Polyflor (Syngenta, France) (2ml.L-1, containing 5 mg.L-1 propiconazole) then incubated at 28°C for 2 days. Colonies were yellow-pigmented, mucoid, and convex, which are morphological characteristics of Xanthomonas spp. colonies. The partial fyuA and gyrB gene sequences were amplified for eight isolated strains (CFBP 9155, CFBP 9156, CFBP 9157, CFBP 9158, CFBP 9159, CFBP 9161, CFBP 9162, and CFBP 9163) using primers of Fargier et al. (2011), and sequenced (Genoscreen, France). The sequences were deposited under numbers OR232891 to OR232898 for fyuA and OR634932 to OR634939 for gyrB. BLASTN analysis of the sequenced fyuA amplicon showed 100% identity and query coverage with the fyuA fragment of Xanthomonas campestris pv. campestris (Xcc) CFBP 6865R (Bellenot et al., 2022). BLASTN analysis of the sequenced gyrB amplicon showed two allelic forms: one showed 100% identity and query coverage with the gyrB fragment of Xcc strain CFBP 6865R (Bellenot et al., 2022), the other one showed 100% identity and query coverage with the type strain Xcc CFBP 5241 (ATCC33913) (Vorhölter et al., 2003). Moreover, two qPCR tools were used to identify the strains successfully as Xcc (Köhl et al., 2011; Rezki et al., 2016) which target the same gene encoding a hypothetical protein and whose primers overlap. The pathogenicity of the eight isolated strains was validated using a bacterial suspension (108 CFU.ml-1) for i) leaf spraying until runoff onto the leaf surfaces of WOSR plants previously maintained at saturated humidity for 48 hours, ii) wound-leaf inoculation of the two youngest true leaves with scissors that had been dipped into the bacterial suspension. Both tests were performed on 3-week-old WOSR plants of the Aviso (INRAE) genotype. Deionized water was used as negative control. Strains CFBP 5241 and the strain CFBP 4954 (Fargier et al., 2007) were used as positive controls for disease expression. Tested plants (seven for spray inoculation and four for wound-leaf inoculation per strain and control condition) were incubated in a greenhouse at 20°C/24°C (night/day). Isolated strains and the strain CFBP 4954 caused yellow lesions with both inoculation methods that necrotized starting about 10 days post inoculation (dpi). The spots coalesced within 14 dpi to form necrotic areas. The type strain CFBP 5241 caused mild symptoms, with only yellow lesions that did not coalesce. Plants inoculated with water remained symptomless. To complete Koch's postulate, re-isolations were achieved. Re-isolated strains on TSA showed the same colony morphology as described above. All re-isolated strains were identified as Xcc based on partial gyrB sequencing and Xcc specific qPCR test (Rezki et al., 2016). This first report in France and the recent identification in Serbia (Popović et al., 2013) may illustrate the emergence of the disease on this crop in Europe. The prevalence and consequences of this disease should be evaluated over a wider geographic area.

Trichoderma viride Colonizes the Roots of Brassica napus L., Alters the Expression of Stress-Responsive Genes, and Increases the Yield of Canola under Field Conditions during Drought

In this work, we present the results of the inoculation of canola seeds (Brassica napus L.) with Trichoderma viride strains that promote the growth of plants. Seven morphologically different strains of T. viride (TvI-VII) were shown to be capable of synthesizing auxins and exhibited cellulolytic and pectinolytic activities. To gain a deeper insight into the molecular mechanisms underlying canola-T. viride interactions, we analyzed the canola stress genes metallothioneins (BnMT1-3) and stringent response genes (BnRSH1-3 and BnCRSH). We demonstrated the presence of cis-regulatory elements responsive to fungal elicitors in the promoter regions of B. napus MT and RSH genes and observed changes in the levels of the transcripts of the above-mentioned genes in response to root colonization by the tested fungal strains. Of the seven tested strains, under laboratory conditions, T. viride VII stimulated the formation of roots and the growth of canola seedlings to the greatest extent. An experiment conducted under field conditions during drought showed that the inoculation of canola seeds with a suspension of T. viride VII spores increased yield by 16.7%. There was also a positive effect of the fungus on the height and branching of the plants, the number of siliques, and the mass of a thousand seeds. We suggest that the T. viride strain TvVII can be used in modern sustainable agriculture as a bioinoculant and seed coating to protect B. napus from drought.

The transcription factor BnaA9.WRKY47 coordinates leaf senescence and nitrogen remobilization in Brassica napus

Nitrogen (N) is an essential macronutrient for plants, and its remobilization is key for adaptation to deficiency stress. However, there is limited understanding of the regulatory mechanisms of N remobilization in the important crop species Brassica napus (oilseed rape). Here, we report the identification of a transcription factor, BnaA9.WRKY47, that is induced by N starvation in a canola variety. At the seedling stage, BnaA9.WRKY47-overexpressing (OE) lines displayed earlier senescence of older leaves and preferential growth of juvenile leaves compared to the wild type under N starvation. At the field scale, the seed yield was significantly increased in the BnaA9.WRKY47-OE lines compared with the wild type when grown under N deficiency conditions and, conversely, it was reduced in BnaA9.WRKY47-knockout mutants. Biochemical analyses demonstrated that BnaA9.WRKY47 directly activates BnaC7.SGR1 to accelerate senescence of older leaves. In line with leaf senescence, the concentration of amino acids in the older leaves of the OE lines was elevated, and the proportion of plant N that they contained was reduced. This was associated with BnaA9.WRKY47 activating the amino acid permease BnaA9.AAP1 and the nitrate transporter BnaA2.NRT1.7. Thus, the expression of BnaA9.WRKY47 efficiently facilitated N remobilization from older to younger leaves or to seeds. Taken together, our results demonstrate that BnaA9.WRKY47 up-regulates the expression of BnaC7.SGR1, BnaA2.NRT1.7, and BnaA9AAP1, thus promoting the remobilization of N in B. napus under starvation conditions.

Genetic improvement of tocotrienol content enhances the oxidative stability of canola oil

Background

Tocotrienols and tocopherols, which are synthesized in plastids of plant cells with similar functionalities, comprise vitamin E to serve as a potent lipid-soluble antioxidant in plants. The synthesis of tocopherols involves the condensation of homogentisic acid (HGA) and phytyl diphosphate (PDP) under the catalysis of homogentisate phytyltransferase (HPT). Tocotrienol synthesis is initiated by the condensation of HGA and geranylgeranyl diphosphate (GGDP) mediated by homogentisate geranylgeranyl transferase (HGGT). As one of the most important oil crops, canola seed is regarded as an ideal plant to efficiently improve the production of vitamin E tocochromanols through genetic engineering approaches. However, only a modest increase in tocopherol content has been achieved in canola seed to date.

Methods

In this study, we transformed barley HGGT (HvHGGT) into canola to improve total tocochromanol content in canola seeds.

Results and discussion

The results showed that the total tocochromanol content in the transgenic canola seeds could be maximally increased by fourfold relative to that in wild-type canola seeds. Notably, no negative impact on important agronomic traits was observed in transgenic canola plants, indicating great application potential of the HvHGGT gene in enhancing tocochromanol content in canola in the future. Moreover, the oil extracted from the transgenic canola seeds exhibited significantly enhanced oxidative stability under high temperature in addition to the increase in total tocochromanol content, demonstrating multiple desirable properties of HvHGGT.

Novel quantitative trait loci from an interspecific Brassica rapa derivative improve pod shatter resistance in Brassica napus

Pod shatter is a trait of agricultural relevance that ensures plants dehisce seeds in their native environment and has been subjected to domestication and selection for non-shattering types in several broadacre crops. However, pod shattering causes a significant yield reduction in canola (Brassica napus L.) crops. An interspecific breeding line BC95042 derived from a B. rapa/B. napus cross showed improved pod shatter resistance (up to 12-fold than a shatter-prone B. napus variety). To uncover the genetic basis and improve pod shatter resistance in new varieties, we analysed F2 and F2:3 derived populations from the cross between BC95042 and an advanced breeding line, BC95041, and genotyped with 15,498 DArTseq markers. Through genome scan, interval and inclusive composite interval mapping analyses, we identified seven quantitative trait loci (QTLs) associated with pod rupture energy, a measure for pod shatter resistance or pod strength, and they locate on A02, A03, A05, A09 and C01 chromosomes. Both parental lines contributed alleles for pod shatter resistance. We identified five pairs of significant epistatic QTLs for additive x additive, additive dominance and dominance x dominance interactions between A01/C01, A03/A07, A07/C03, A03/C03, and C01/C02 chromosomes for rupture energy. QTL effects on A03/A07 and A01/C01 were in the repulsion phase. Comparative mapping identified several candidate genes (AG, ABI3, ARF3, BP1, CEL6, FIL, FUL, GA2OX2, IND, LATE, LEUNIG, MAGL15, RPL, QRT2, RGA, SPT and TCP10) underlying main QTL and epistatic QTL interactions for pod shatter resistance. Three QTLs detected on A02, A03, and A09 were near the FUL (FRUITFULL) homologues BnaA03g39820D and BnaA09g05500D. Focusing on the FUL, we investigated putative motifs, sequence variants and the evolutionary rate of its homologues in 373 resequenced B. napus accessions of interest. BnaA09g05500D is subjected to purifying selection as it had a low Ka/Ks ratio compared to other FUL homologues in B. napus. This study provides a valuable resource for genetic improvement for yield through an understanding of the genetic mechanism controlling pod shatter resistance in Brassica species.

Bacillus paralicheniformis 2R5 and its impact on canola growth and N-cycle genes in the rhizosphere

Chemical fertilization has a negative impact on the natural environment. Plant growth-promoting (PGP) rhizobacterial biofertilizers can be a safer alternative to synthetic agrochemicals. In this research, a culture-based method was used to assess the population size of rhizobacteria at the vegetative, flowering, and maturity stages of canola. Rhizobacteria were then isolated from each of the canola growth stages, and their seven PGP traits were determined. The highest abundance of culturable bacteria was found at the vegetative stage of the plants. Furthermore, four out of seven PGP traits were produced by the highest % of isolates at the vegetative stage. In the greenhouse experiment that included six rhizobacterial strains with best PGP traits, the greatest canola growth promotion ability under sterile conditions was observed after the introduction of Bacillus paralicheniformis 2R5. Moreover, under nonsterile conditions, 2R5 significantly increased canola growth. The presence of the trpA, B, C, D, E, F and pstA, and S genes in the 2R5 genome could be associated with canola growth promotion abilities. The chiA and mbtH genes could contribute to 2R5 antifungal activity against fungal pathogens. Moreover, the introduction of 2R5 significantly increased the abundance of the narG, nosZ, nifH, and nirS genes, which can prove that the 2R5 strain may be an important member of the soil bacterial community.

Cloning and Functional Characterization of Cold-Inducible MYB-like 17 Transcription Factor in Rapeseed (Brassica napus L.)

Rapeseed (Brassica napus L.) is an important crop for edible oil, vegetables, and biofuel. Rapeseed growth and development require a minimum temperature of ~1-3 °C. Notably, frost damage occurs during overwintering, posing a serious threat to the productivity and yield of rapeseed. MYB proteins are important transcription factors (TFs) in plants, and have been proven to be involved in the regulation of stress responses. However, the roles of the MYB TFs in rapeseed under cold stress conditions are yet to be fully elucidated. To better understand the molecular mechanisms of one MYB-like 17 gene, BnaMYBL17, in response to low temperature, the present study found that the transcript level of BnaMYBL17 is induced by cold stress. To characterize the gene's function, the 591 bp coding sequence (CDS) from rapeseed was isolated and stably transformed into rapeseed. The further functional analysis revealed significant sensitivity in BnaMYBL17 overexpression lines (BnaMYBL17-OE) after freezing stress, suggesting its involvement in freezing response. A total of 14,298 differentially expressed genes relative to freezing response were found based on transcriptomic analysis of BnaMYBL17-OE. Overall, 1321 candidate target genes were identified based on differential expression, including Phospholipases C1 (PLC1), FCS-like zinc finger 8 (FLZ8), and Kinase on the inside (KOIN). The qPCR results confirmed that the expression levels of certain genes showed fold changes ranging from two to six when compared between BnaMYBL17-OE and WT lines after exposure to freezing stress. Furthermore, verification indicated that BnaMYBL17 affects the promoter of BnaPLC1, BnaFLZ8, and BnaKOIN genes. In summary, the results suggest that BnaMYBL17 acts as a transcriptional repressor in regulating certain genes related to growth and development during freezing stress. These findings provide valuable genetic and theoretical targets for molecular breeding to enhance freezing tolerance in rapeseed.

Brassica napus Haploid and Double Haploid Production and Its Latest Applications

Rapeseed is one of the most important oil crops in the world. Increasing demand for oil and limited agronomic capabilities of present-day rapeseed result in the need for rapid development of new, superior cultivars. Double haploid (DH) technology is a fast and convenient approach in plant breeding as well as genetic research. Brassica napus is considered a model species for DH production based on microspore embryogenesis; however, the molecular mechanisms underlying microspore reprogramming are still vague. It is known that morphological changes are accompanied by gene and protein expression patterns, alongside carbohydrate and lipid metabolism. Novel, more efficient methods for DH rapeseed production have been reported. This review covers new findings and advances in Brassica napus DH production as well as the latest reports related to agronomically important traits in molecular studies employing the double haploid rapeseed lines.

Genomic asymmetry of the Brassica napus seed: epigenetic contributions of DNA methylation and small RNAs to subgenome bias

Polyploidy is a persistent phenomenon in angiosperm genome evolution that is hypothesized to have contributed to the diversity of extant flowering plants. Brassica napus, one of the world's most important angiosperm oilseed species, originated from the interspecific hybridization of Brassica rapa (Aⁿ ) and Brassica oleracea (Cⁿ ). While the trends of genome dominance in transcriptomics are beginning to emerge, less is known about the epigenetic and small RNA landscapes in polyploids during reproductive development. The seed is the pivotal developmental transition into the new sporophytic generation, and experiences substantial epigenetic modifications over time. Here, we investigated the prevalence of bias in the contexts of DNA methylation and small interfering (si)RNA profiles in both subgenomes (Aⁿ and Cⁿ ), as well as the ancestral fractionated genomes across B. napus seed development. We report ubiquitous Cⁿ subgenome bias of siRNA expression and cytosine methylation, with DNA methylation being particularly abundant on gene promoters in the Cⁿ subgenome. Further, we provide evidence that siRNA transcriptional patterns were conserved within the ancestral triplicated subgenomes of B. napus, but not across the Aⁿ and Cⁿ subgenomes. We discuss how methylation patterns in the B. napus seed relate to genes, promoter regions, siRNA loci and transposable elements through the lens of genome fractionation and polyploidization. Taken together we provide evidence for epigenetic regulation selectively silencing the Cⁿ subgenome during seed development, and explore the impact of genome fractionation on the epigenetic components of the B. napus seed.

The Highly Embryogenic Brassica napus DH4079 Line Is Recalcitrant to Agrobacterium-Mediated Genetic Transformation

Brassica napus is a species of high agronomic interest, used as a model to study different processes, including microspore embryogenesis. The DH4079 and DH12075 lines show high and low embryogenic response, respectively, which makes them ideal to study the basic mechanisms controlling embryogenesis induction. Therefore, the availability of protocols for genetic transformation of these two backgrounds would help to generate tools to better understand this process. There are some reports in the literature showing the stable transformation of DH12075. However, no equivalent studies in DH4079 have been reported to date. We explored the ability of DH4079 plants to be genetically transformed. As a reference to compare with, we used the same protocols to transform DH12075. We used three different protocols previously reported as successful for B. napus stable transformation with Agrobacterium tumefaciens and analyzed the response of plants. Whereas DH12075 plants responded to genetic transformation, DH4079 plants were completely recalcitrant, not producing any single regenerant out of the 1784 explants transformed and cultured. Additionally, an Agrobacterium rhizogenes transient transformation assay was performed on both lines, and only DH12075, but no DH4079 seedlings, responded to A. rhizogenes infection. Therefore, we propose that the DH4079 line is recalcitrant to Agrobacterium-mediated transformation.

Mesophyll conductance and N allocation co-explained the variation in photosynthesis in two canola genotypes under contrasting nitrogen supply

The application of nitrogen fertilizer within a normal range has been found to increase the leaf nitrogen content and photosynthetic rate of canola plants (Brassica napus L.). Despite numerous studies on the separate effects of CO₂ diffusion limitation and nitrogen allocation trade-off on photosynthetic rate, few have examined both these factors in relation to the photosynthetic rate of canola. In this study, two genotypes of canola with varying leaf nitrogen content were analyzed to determine the impact of nitrogen supply on leaf photosynthesis, mesophyll conductance, and nitrogen partitioning. The results showed that the CO₂ assimilation rate (A), mesophyll conductance (g _m), and photosynthetic nitrogen content (N _psn) increased with an increase in nitrogen supply in both genotypes. The relationship between nitrogen content and A followed a linear-plateau regression, while A had linear relationships with both photosynthetic nitrogen content and g _m, indicating that the key to enhancing A is increasing the distribution of leaf nitrogen into the photosynthetic apparatus and g _m, rather than just increasing nitrogen content. Under high nitrogen treatment, the genotype (QZ) with high nitrogen content had 50.7% more nitrogen than the other genotype (ZY21), but had similar A, which was primarily due to ZY21's higher photosynthetic nitrogen distribution ratio and stomatal conductance (g _sw). On the other hand, QZ showed a higher A than ZY21 under low nitrogen treatment as QZ had higher N _psn and g _m compared to ZY21. Our results indicate that, in selecting high PNUE rapeseed varieties, it is important to consider the higher photosynthetic nitrogen distribution ratio and CO₂ diffusion conductance.

P450-mediated resistance in Myzus persicae (Sulzer) (Hemiptera: Aphididae) reduces the efficacy of neonicotinoid seed treatments in Brassica napus

BACKGROUND

The prophylactic use of seeds treated with neonicotinoid insecticides remains an important means of controlling aphid pests in canola (Brassica napus) crops in many countries. Yet, one of the most economically important aphid species worldwide, the peach potato aphid (Myzus persicae), has evolved mechanisms which confer resistance to neonicotinoids, including amplification of the cytochrome P450 gene, CYP6CY3. While CYP6CY3 amplification has been associated with low-level resistance to several neonicotinoids in laboratory acute toxicity bioassays, its impact on insecticide efficacy in the field remains unresolved. In this study, we investigated the impact of CYP6CY3 amplification on the ability of M. persicae to survive neonicotinoid exposure under laboratory and semi-field conditions.

RESULTS

Three M. persicae clones, possessing different copy numbers of CYP6CY3, were shown to respond differently when exposed to the neonicotinoids, imidacloprid and thiamethoxam, in laboratory bioassays. Two clones, EastNaernup209 and Osborne171, displayed low levels of resistance (3-20-fold), which is consistent with previous studies. However, in a large-scale semi-field trial, both clones showed a surprising ability to survive and reproduce on B. napus seedlings grown from commercial rates of neonicotinoid-treated seed. In contrast, an insecticide-susceptible clone, of wild-type CYP6CY3 copy number, was unable to survive on seedlings treated in the same manner.

CONCLUSION

Our findings suggest that amplification of CYP6CY3 in M. persicae clones substantially impairs the efficacy of neonicotinoid seed treatments when applied to B. napus. These findings highlight the potentially important real-world implications of resistances typically considered to be 'low level' as defined through laboratory bioassays. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Brassica napus Plants Gain Improved Salt-Stress Tolerance and Increased Storage Oil Biosynthesis by Interfering with CRL3BPM Activities

Generating new strategies to improve plant performance and yield in crop plants becomes increasingly relevant with ongoing and predicted global climate changes. E3 ligases that function as key regulators within the ubiquitin proteasome pathway often are involved in abiotic stress responses, development, and metabolism in plants. The aim of this research was to transiently downregulate an E3 ligase that uses BTB/POZ-MATH proteins as substrate adaptors in a tissue-specific manner. Interfering with the E3 ligase at the seedling stage and in developing seeds results in increased salt-stress tolerance and elevated fatty acid levels, respectively. This novel approach can help to improve specific traits in crop plants to maintain sustainable agriculture.

Identification of candidate genes for LepR1 resistance against Leptosphaeria maculans in Brassica napus

Utilising resistance (R) genes, such as LepR1, against Leptosphaeria maculans, the causal agent of blackleg in canola (Brassica napus), could help manage the disease in the field and increase crop yield. Here we present a genome wide association study (GWAS) in B. napus to identify LepR1 candidate genes. Disease phenotyping of 104 B. napus genotypes revealed 30 resistant and 74 susceptible lines. Whole genome re-sequencing of these cultivars yielded over 3 million high quality single nucleotide polymorphisms (SNPs). GWAS in mixed linear model (MLM) revealed a total of 2,166 significant SNPs associated with LepR1 resistance. Of these SNPs, 2108 (97%) were found on chromosome A02 of B. napus cv. Darmor bzh v9 with a delineated LepR1_mlm1 QTL at 15.11-26.08 Mb. In LepR1_mlm1, there are 30 resistance gene analogs (RGAs) (13 nucleotide-binding site-leucine rich repeats (NLRs), 12 receptor-like kinases (RLKs), and 5 transmembrane-coiled-coil (TM-CCs)). Sequence analysis of alleles in resistant and susceptible lines was undertaken to identify candidate genes. This research provides insights into blackleg resistance in B. napus and assists identification of the functional LepR1 blackleg resistance gene.

Canola with Stacked Genes Shows Moderate Resistance and Resilience against a Field Population of Plasmodiophora brassicae (Clubroot) Pathotype X

Genetic resistance is a cornerstone for managing clubroot (Plasmodiophora brassicae). However, when used repeatedly, a clubroot resistance (CR) gene can be broken rapidly. In this study, canola inbred/hybrid lines carrying one or two CR genes (Rcr1/CRa^M and Crr1^rutb) were assessed against P. brassicae pathotype X by repeated exposure to the same inoculum source under a controlled environment. Lines carrying two CR genes, either Rcr1 + Crr1^rutb or CRa^M + Crr1^rutb, showed partial resistance. Selected lines were inoculated with a field pathotype X population (L-G3) at 5 × 10⁶ resting spores/g soil, and all clubs were returned to the soil they came from six weeks after inoculation. The planting was repeated for five cycles, with diseased roots being returned to the soil after each cycle. The soil inoculum was quantified using qPCR before each planting cycle. All lines with a single CR gene were consistently susceptible, maintaining high soil inoculum levels over time. The lines carrying two CR genes showed much lower clubroot severity, resulting in a 10-fold decline in soil inoculum. These results showed that the CR-gene stacking provided moderate resistance against P. brassicae pathotype X, which may also help reduce the pathogen inoculum buildup in soil.

Quantitative Trait Loci for Genotype and Genotype by Environment Interaction Effects for Seed Yield Plasticity to Terminal Water-Deficit Conditions in Canola (Brassica napus L.)

Canola plants suffer severe crop yield and oil content reductions when exposed to water-deficit conditions, especially during the reproductive stages of plant development. There is a pressing need to develop canola cultivars that can perform better under increased water-deficit conditions with changing weather patterns. In this study, we analysed genetic determinants for the main effects of quantitative trait loci (QTL), (Q), and the interaction effects of QTL and Environment (QE) underlying seed yield and related traits utilising 223 doubled haploid (DH) lines of canola in well-watered and water-deficit conditions under a rainout shelter. Moderate water-deficit at the pre-flowering stage reduced the seed yield to 40.8%. Multi-environmental QTL analysis revealed 23 genomic regions associated with days to flower (DTF), plant height (PH) and seed yield (SY) under well-watered and water-deficit conditions. Three seed yield QTL for main effects were identified on chromosomes A09, C03, and C09, while two were related to QE interactions on A02 and C09. Two QTL regions were co-localised to similar genomic regions for flowering time and seed yield (A09) and the second for plant height and chlorophyll content. The A09 QTL was co-located with a previously mapped QTL for carbon isotope discrimination (Δ¹³C) that showed a positive relationship with seed yield in the same population. Opposite allelic effects for plasticity in seed yield were identified due to QE interactions in response to water stress on chromosomes A02 and C09. Our results showed that QTL's allelic effects for DTF, PH, and SY and their correlation with Δ¹³C are stable across environments (field conditions, previous study) and contrasting water regimes (this study). The QTL and DH lines that showed high yield under well-watered and water-deficit conditions could be used to manipulate water-use efficiency for breeding improved canola cultivars.

juncea), and Other Brassicaceae Crops

Alternaria leaf spot (Alternaria brassicae) can be a devastating disease in canola (Brassica napus) and mustard (B. juncea), but there are no highly effective host resistances available. Screening of 150 diverse Brassicaceae varieties under glasshouse conditions highlighted important novel resistances. In particular, Camelina sativa '4076' and Diplotaxis erucoides 'Wasabi Rocket' had complete resistance across disease assessment parameters (leaf incidence [%LDI]; severity [%LAD]; consequent defoliation [%LCI]). The next most resistant varieties were C. sativa 'CSA' (%LDI 0.6; %LAD 0.4), '4144' (%LDI 1.2; %LAD 0.5), '405' (%LDI 1.7; %LAD 0.7), C. sativa '3274' (%LDI 2.5; %LAD 0.8), Carrichtera annua 'CAN3' (%LDI 7.7; %LAD 4.0), and Sisymbrium irio 'London Rocket' (%LDI 2.1; %LAD 0.8), all with %LCI values of 0. Other genotypes showing high-level resistance included S. erysimoides 'SER 4' (%LDI 11.8; %LAD 5.6; %LCI 0) and D. cardaminoides 'Wild Rocket' (%LDI 15.5; %LAD 7.2; %LCI 0), and those showing moderate resistance were Brassica carinata 'ML-EM-1' (Rungwe), B. insularis 'Moris', B. napus 'ZY006', B. oxyrrhina 'BOX1', B. oleracea var. capitata 'Sugarloaf', B. tournefortii 'CN01-104-2', and Sinapis alba 'Concerta' with %LDI 21.6 to 29.8, %LAD 12.8 to 21.0, and %LCI 0 to 5.7. In particular, B. napus 'ZY006' for canola and B. oleracea var. capitata 'Sugarloaf' can now be directly utilized (i.e., without crossing impairment) for Brassica species and vegetable breeding programs, respectively. While all B. juncea genotypes were susceptible, there were some less susceptible varieties from India in comparison with genotypes from Australia or China. The most susceptible test genotype was Rapistrum sativus (%LDI 89.4; %LAD 83.9; %LCI 71.0), highlighting the value of the resistances identified. These findings not only highlight a range of novel resistances against A. brassicae for canola, mustard, and other diverse Brassicaceae breeding programs to develop resistant commercial varieties, but also emphasize highly susceptible varieties to avoid in both breeding programs and commercial situations conducive to Alternaria leaf spot.

Management of Reniform Nematode in Cotton Using Winter Crop Residue Amendments Under Greenhouse Conditions

Rotylenchulus reniformis (reniform nematode, RN) is among the most important nematodes affecting cotton. Cultural practices, such as rotation and soil amendment, are established methods for managing RN. Management may be enhanced if crop residue has biofumigant properties against RN. The objective was to evaluate the efficacy of winter crop amendments for managing RN in the greenhouse. Reniform nematode-infested soil was amended with dry or fresh organic matter (OM, 2% w/w) from winter crops - canola, carinata, hairy vetch, oat, or no crop. Cotton was subsequently grown in this soil. Independent of the crop, dry OM amendments were more effective than no amendment at managing RN, while fresh OM amendments were not. Soil and root RN abundances and reproduction factors were generally lower in Trials 1 and 3 for dry OM than fresh OM amendments or control without OM. In Trial 2, none of the OM treatments reduced RN parameters compared with no OM control. In general, when compared to plants without RN or OM, RN did not produce significant changes in growth parameters but did affect physiology (Soil Plant Analysis Development, or SPAD, values). In conclusion, dry OM amendments can help manage RN, crop growth does not always relate to RN abundances, and SPAD values could help indicate RN presence.

Blackleg Yield Losses and Interactions with Verticillium Stripe in Canola (Brassica napus) in Canada

Blackleg, caused by Leptosphaeria maculans, is an important disease of canola (Brassica napus). The pathogen can attack stems, leaves and pods, but basal stem cankers are most damaging and can result in significant yield losses. In Canada, Verticillium stripe (Verticillium longisporum) has recently emerged as another disease threat to canola. Symptoms of Verticillium stripe can resemble those of blackleg, and the two diseases may occur together. The effect of blackleg on yield was explored in field experiments with two canola hybrids and by evaluating a wider variety of hybrids in commercial crops in central Alberta, Canada. The impact on yield of L. maculans/V. longisporum interactions was also assessed under field and greenhouse conditions. In most hybrids, the relationship between blackleg severity and yield components was best explained by second-degree quadratic equations, although a linear relationship was found for one variety sampled in commercial fields. When L. maculans was co-inoculated with V. longisporum, blackleg severity and yield losses increased. In some cases, Verticillium stripe caused greater yield losses than blackleg. The results suggest that the interaction between L. maculans/V. longisporum may cause more severe losses in canola, highlighting the need for proactive disease management strategies.

Optimal Contribution Selection Improves the Rate of Genetic Gain in Grain Yield and Yield Stability in Spring Canola in Australia and Canada

Crop breeding must achieve higher rates of genetic gain in grain yield (GY) and yield stability to meet future food demands in a changing climate. Optimal contributions selection (OCS) based on an index of key economic traits should increase the rate of genetic gain while minimising population inbreeding. Here we apply OCS in a global spring oilseed rape (canola) breeding program during three cycles of S_0,1 family selection in 2016, 2018, and 2020, with several field trials per cycle in Australia and Canada. Economic weights in the index promoted high GY, seed oil, protein in meal, and Phoma stem canker (blackleg) disease resistance while maintaining plant height, flowering time, oleic acid, and seed size and decreasing glucosinolate content. After factor analytic modelling of the genotype-by-environment interaction for the additive effects, the linear rate of genetic gain in GY across cycles was 0.059 or 0.087 t ha^-1 y^-1 (2.9% or 4.3% y^-1) based on genotype scores for the first factor (f₁) expressed in trait units or average predicted breeding values across environments, respectively. Both GY and yield stability, defined as the root-mean-square deviation from the regression line associated with f₁, were predicted to improve in the next cycle with a low achieved mean parental coancestry (0.087). These methods achieved rapid genetic gain in GY and other traits and are predicted to improve yield stability across global spring canola environments.

Critical values of soil solution Al3+ activity and pH for canola and maize cultivation in two acidic soils

BACKGROUND

Aluminum (Al) toxicity caused by soil acidification is the main constraint for crop growth in tropical and subtropical areas of southern China. The critical values of soil solution Al³⁺ activity and pH for crops in acidic soils can provide a useful reference for soil acidity amelioration.

RESULTS

A pot experiment in a greenhouse was conducted to investigate the critical values of soil solution Al³⁺ activity and pH for canola and maize in an Ultisol and an Alfisol. The critical values of soil solution Al³⁺ activity in Ultisol and Alfisol for canola were 1.5 and 10.0 μmol L^-1 , and 13.9 and 30.4 μmol L^-1 for maize, respectively. The Al tolerance varied with soil type for the same variety of crop. There was more biomass of roots and shoots and higher plant height under the same Al³⁺ activity, and thus greater critical values of soil solution Al³⁺ activity for both crops in Alfisol than those in Ultisol, owing to higher Ca²⁺ /Al³⁺ , Mg²⁺ /Al³⁺ and K⁺ /Al³⁺ ratios in soil solution caused by higher cation exchange capacity and exchangeable base cations in Alfisol, when compared with those in Ultisol. The critical values of soil solution pH for canola and maize in Ultisol were 5.09 and 4.72, respectively; while those in Alfisol were 4.87 and 4.54, respectively.

CONCLUSION

The critical values of Al³⁺ activity were higher for maize than for canola and the critical values for both crops were higher in Alfisol than in Ultisol. The critical soil pH for both crops showed opposite trends to soil Al³⁺ activity. © 2022 Society of Chemical Industry.

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.

Nitrogen isotope discrimination in open-pollinated and hybrid canola suggests indirect selection for enhanced ammonium utilization

Nitrogen isotope discrimination (Δ¹⁵N) may have utility as an indicator of nitrogen use in plants. A simple Δ¹⁵N-based isotope mass balance (IMB) model has been proposed to provide estimates of efflux/influx (E/I) ratios across root plasma membranes, the proportion of inorganic nitrogen assimilation in roots (P _root) and translocation of inorganic nitrogen to shoots (Ti/Tt) under steady-state conditions. We used the IMB model to investigate whether direct selection for yield in canola (Brassica napus L.) has resulted in indirect selection in traits related to nitrogen use. We selected 23 canola lines developed from 1942 to 2017, including open-pollinated (OP) lines developed prior to 2005 as well as more recent commercial hybrids (CH), and in three separate experiments grew them under hydroponic conditions in a greenhouse with either 0.5 mM ammonium, 0.5 mM nitrate, or 5 mM nitrate. Across all lines, E/I, P_root and Ti/Tt averaged 0.09±0.03, 0.82±0.05 and 0.23±0.06 in the low nitrate experiment, and 0.31±0.06, 0.71±0.07 and 0.42±0.12 in the high nitrate experiment, respectively. In contrast, in the ammonium experiment average E/I was 0.40±0.05 while Ti/Tt averaged 0.07±0.04 and P_root averaged 0.97±0.02. Although there were few consistent differences between OP and CH under nitrate nutrition, commercial hybrids were collectively better able to utilize ammonium as their sole nitrogen source, demonstrating significantly greater overall biomass and a lower P_root and a higher Ti/Tt, suggesting a somewhat greater flux of ammonium to the shoot. Average root and whole-plant Δ¹⁵N were also slightly higher in CH lines, suggesting a small increase in E/I. An increased ability to tolerate and/or utilize ammonium in modern canola hybrids may have arisen under intensive mono-cropping.

Flavonoids and Devosia sp SL43 cell-free supernatant increase early plant growth under salt stress and optimal growth conditions

Salt stress is a major threat to modern agriculture, significantly affecting plant growth and yield, and causing substantial economic losses. At this crucial time of increasing climate change conditions, soil salinity will continue to develop and become an even more serious challenge to crop agriculture. Hence, there is a pressing need for sustainable techniques in agricultural production that could meet the dual challenges of crop productivity and environmental instability. The use of biostimulants in agricultural production has greatly influenced plant health and global food production. In particular, the application of bioactive materials produced by beneficial microbes is becoming a common practice in agriculture and provides numerous benefits to plant growth and resistance to stressful conditions. In this research two biostimulants; a type of plant secondary metabolite (flavonoids) and a microbe-based material (CFS: Cell-Free Supernatant) containing active compounds secreted by a novel bacterial strain isolated from Amphecarpaea bracteata root nodules (Devosia sp - SL43), have been utilized to improve the growth and stress resistance of two major oil seed crops; canola and soybean, under optimal and salt stress conditions. Our findings suggested significant improvements in crop growth of canola and soybean following the application of both biostimulants. Under optimal growth conditions, soybean growth was significantly affected by foliar spray of flavonoids with increases in shoot fresh and dry weight, and leaf area, by 91, 99.5, and 73%, respectively. However, soybean growth was unaffected by flavonoids under salt stress. In contrast, CFS with a meaningful capacity to mitigate the negative effects of salinity stress improved soybean shoot fresh biomass, dry biomass, and leaf area by 128, 163 and 194%, respectively, under salt stress conditions. Canola was less responsive to both biostimulants, except for canola root variables which were substantially improved by flavonoid spray. Since this was the first assessment of these materials as foliar sprays, we strongly encourage further experimentation to confirm the findings reported here and to determine the full range of applicability of each of these potential technologies.

Selected Properties of Two Alternative Plant Fibers: Canola and Sweet Clover Fibers

Identifying sustainable resources of natural fibers is essential due to their high demand in industrial applications such as automotive and biomedical materials. Two alternative fibers obtained from canola and sweet clover stalks were characterized for their properties using energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), contact angle, and tensile test. Hemp and flax fibers, both in use as industrial fibers, were also characterized as conventional fibers. Results showed that all the fibers had the same chemical elements (carbon, oxygen, magnesium, and potassium) and chemical bonds. The crystallinity index for the alternative fibers ranged from 62 to 71%, which was close but lower than the conventional fibers (82% for hemp and 80% for flax). The thermal stability of the alternative fibers was around 220 °C, close to the conventional fibers (230 °C). The alternative fibers had contact angles of less than 90°, showing high surface energy. Since the alternative fibers had a low Young's modulus and tensile strength (5.57-8.52 GPa and 57.45-71.26 MPa, respectively), they are suitable for some specific applications in the biomedical industry. In contrast, conventional fibers are suitable where a higher stiffness and strength is required.

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.

Twenty Years of Leptosphaeria maculans Population Survey in France Suggests Pyramiding Rlm3 and Rlm7 in Rapeseed Is a Risky Resistance Management Strategy

Strategies for plant resistance gene deployment aim to preserve their durability to highly adaptable fungal pathogens. While the pyramiding of resistance genes is often proposed as an effective way to increase their durability, molecular mechanisms by which the pathogen can overcome the resistance also are important aspects to take into account. Here, we report a counterexample where pyramiding of two resistance genes of Brassica napus, Rlm3 and Rlm7, matching the Leptosphaeria maculans avirulence genes AvrLm3 and AvrLm4-7, respectively, favored the selection of double-virulent isolates. We previously demonstrated that the presence of a functional AvrLm4-7 gene in an isolate masks the Rlm3-AvrLm3 recognition. Rlm7 was massively deployed in France since 2004. L. maculans populations were surveyed on a large scale (>7,600 isolates) over a period of 20 years, and resistance gene deployment at the regional scale was determined. Mutations in isolates overcoming both resistance genes were analyzed. All data indicated that the simultaneous success of Rlm7, the deployment of varieties pyramiding Rlm3 and Rlm7, along with the decrease in areas cultivated with Rlm3 only, contributed to the success of virulent isolates toward Rlm7, and more recently to both Rlm3 and Rlm7. Experimental field assays proved that resistance gene alternation was a better strategy compared with pyramiding in this context. Our study also illustrated an unusually high sequence diversification of AvrLm3 and AvrLm4-7 under such a selection pressure, and identified a few regions of the AvrLm4-7 protein involved in both its recognition by Rlm7 and in its AvrLm3-Rlm3 masking ability. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Meal nutritional characteristics and oil profile of sprouted, dehulled, and solvent-extracted canola

BACKGROUND

Canola meal has limited utilization in feed and food applications because of the presence of antinutritional factors and a high fiber content. Thus, the present study used 3-day canola seed sprouting followed by hull removal to improve the nutritional quality of canola as a feed and food ingredient to further enhance and diversify the canola market.

RESULTS

Seed sprouting and the hull removal process resulted in 63.2% sprouts, 29.3% mix fractions (MF) (hulls, ungerminated seed, and delayed sprouts) and 8.1% mass loss during sprouting. Fresh sprouts and MF were dried, ground and defatted to compare the obtained meals and oils with their counterparts of raw seed. Defatted sprouts (DFSP) resulted in a 46.2% reduction in crude fiber, a 34.3% reduction in acid detergent fiber and a 43.4% reduction in neutral detergent fiber compared to defatted raw seed (DFSE). DFSP provided a 10.1% higher protein content and a 5.9% increase in total amino acid content with higher essential amino acids compared to DFSE. Total carbohydrate was lowered by 5.5%, phytic acid content was lowered by 25.9%, and ash content was lowered by 5.5% in DFSP, whereas total glucosinolate content was higher in DFSP (13.1 μmol g^-1 ) than in DFSE (8.8 μmol g^-1 ). Sprouts and MF showed an oil content of 38.4% and 9.6%, respectively, compared to raw seed (34.5%).

CONCLUSION

Sprouting and hull removal of canola seed can potentially provide nutritive meal for food and feed applications. © 2022 Society of Chemical Industry.

Production of quorum sensing-related metabolites and phytoalexins during Pseudomonas aeruginosa-Brassica napus interaction

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that has been shown to interact with many organisms throughout the domains of life, including plants. How this broad-host-range bacterium interacts with each of its diverse hosts, especially the metabolites that mediate these interactions, is not completely known. In this work, we used a liquid culture root infection system to collect plant and bacterial metabolites on days 1, 3 and 5 post-P. aeruginosa (strain PA14) infection of the oilseed plant, canola (Brassica napus). Using MS-based metabolomics approaches, we identified the overproduction of quorum sensing (QS)-related (both signalling molecules and regulated products) metabolites by P. aeruginosa while interacting with canola plants. However, the P. aeruginosa infection induced the production of several phytoalexins, which is a part of the hallmark plant defence response to microbes. The QS system of PA14 appears to only mediate part of the canola-P. aeruginosa metabolomic interactions, as the use of isogenic mutant strains of each of the three QS signalling branches did not significantly affect the induction of the phytoalexin brassilexin, while induction of spirobrassinin was significantly decreased. Interestingly, a treatment of purified QS molecules in the absence of bacteria was not able to induce any phytoalexin production, suggesting that active bacterial colonization is required for eliciting phytoalexin production. Furthermore, we identified that brassilexin, the only commercially available phytoalexin that was detected in this study, demonstrated a MIC of 400 µg ml^-1 against P. aeruginosa PA14. The production of phytoalexins can be an effective component of canola innate immunity to keep potential infections by the opportunistic pathogen P. aeruginosa at bay.

Brassica napus genes Rlm4 and Rlm7, conferring resistance to Leptosphaeria maculans, are alleles of the Rlm9 wall-associated kinase-like resistance locus

Brassica napus (canola/rapeseed) race specific resistance genes against blackleg disease, caused by the ascomycete fungus Leptosphaeria maculans, have been commonly used in canola breeding. To date; LepR3, Rlm2 and Rlm9 R genes against L. maculans have been cloned from B. napus. LepR3 and Rlm2 are Receptor Like Proteins (RLP) and the recently reported Rlm9 is a Wall Associated Kinase-Like (WAKL) protein. Rlm9 located on chromosome A07 is closely linked with Rlm3, Rlm4, RLm7 genes. Recognition of AvrLm5-9 and AvrLm3 by their corresponding Rlm9 and Rlm3 proteins is masked in the presence of AvrLm4-7. Here we report cloning of Rlm4 and Rlm7 by generating genome sequence of the doubled haploid (DH) B. napus cv Topas DH16516 introgression lines Topas-Rlm4 and Topas-Rlm7. Candidate Rlm4 and Rlm7 genes were identified form the genome sequence and gene structures were determined by mapping RNA-sequence reads, generated from infected cotyledon tissues, to the genome of Topas-Rlm4 and Topas-Rlm7. Rlm4 and Rlm7 genomic constructs with their native promoters were transferred into the blackleg susceptible B. napus cv Westar N-o-1. Complementation of resistance response in the transgenic Westar:Rlm4 and Westar:Rlm7 that were inoculated with L. maculans transgenic isolates 2367:AvrRlm4-7 or 2367:AvrLm7 confirmed the function of Rlm4 and Rlm7 genes. Wild type L. maculans isolate 2367 that does not contain AvrLm4-7 or AvrLm7, and transgenic 2367:AvrLm3 and 2367:AvrLm5-9 did not induce resistance proving the specificity of Rlm4 and Rlm7 response. Rlm4 and Rlm7 alleles are also allelic to Rlm9. Rlm4 and Rlm7 genes encode WAKL proteins. Comparison of highly homologous sequences of Rlm4 and Rlm7 with each other and with the sequence of additional alleles, using whole genome sequencing of additional 128 lines, identified a limited number of point mutation located within the predicted extracellular receptor domains.

Brassica napus Bacterial Assembly Processes Vary with Plant Compartment and Growth Stage but Not between Lines

Holobiont bacterial community assembly processes are an essential element to understanding the plant microbiome. To elucidate these processes, leaf, root, and rhizosphere samples were collected from eight lines of Brassica napus in Saskatchewan over the course of 10 weeks. We then used ecological null modeling to disentangle the community assembly processes over the growing season in each plant part. The root was primarily dominated by stochastic community assembly processes, which is inconsistent with previous studies that suggest of a highly selective root environment. Leaf assembly processes were primarily stochastic as well. In contrast, the rhizosphere was a highly selective environment. The dominant rhizosphere selection process leads to more similar communities. Assembly processes in all plant compartments were dependent on plant growth stage with little line effect on community assembly. The foundations of assembly in the leaf were due to the harsh environment, leading to dominance of stochastic effects, whereas the stochastic effects in the root interior likely arise due to competitive exclusion or priority effects. Engineering canola microbiomes should occur during periods of strong selection assuming strong selection could promote beneficial bacteria. For example, engineering the microbiome to resist pathogens, which are typically aerially born, should focus on the flowering period, whereas microbiomes to enhance yield should likely be engineered postflowering as the rhizosphere is undergoing strong selection. IMPORTANCE In order to harness the microbiome for more sustainable crop production, we must first have a better understanding of microbial community assembly processes that occurring during plant development. This study examines the bacterial community assembly processes of the leaf, root, and rhizosphere of eight different lines of Brassica napus over the growing season. The influence of growth stage and B. napus line were examined in conjunction with the assembly processes. Understanding what influences the assembly processes of crops might allow for more targeted breeding efforts by working with the plant to manipulate the microbiome when it is undergoing the strongest selection pressure.

Two independent approaches converge to the cloning of a new Leptosphaeria maculans avirulence effector gene, AvrLmS-Lep2

Brassica napus (oilseed rape, canola) seedling resistance to Leptosphaeria maculans, the causal agent of blackleg (stem canker) disease, follows a gene-for-gene relationship. The avirulence genes AvrLmS and AvrLep2 were described to be perceived by the resistance genes RlmS and LepR2, respectively, present in B. napus 'Surpass 400'. Here we report cloning of AvrLmS and AvrLep2 using two independent methods. AvrLmS was cloned using combined in vitro crossing between avirulent and virulent isolates with sequencing of DNA bulks from avirulent or virulent progeny (bulked segregant sequencing). AvrLep2 was cloned using a biparental cross of avirulent and virulent L. maculans isolates and a classical map-based cloning approach. Taking these two approaches independently, we found that AvrLmS and AvrLep2 are the same gene. Complementation of virulent isolates with this gene confirmed its role in inducing resistance on Surpass 400, Topas-LepR2, and an RlmS-line. The gene, renamed AvrLmS-Lep2, encodes a small cysteine-rich protein of unknown function with an N-terminal secretory signal peptide, which is a common feature of the majority of effectors from extracellular fungal plant pathogens. The AvrLmS-Lep2/LepR2 interaction phenotype was found to vary from a typical hypersensitive response through intermediate resistance sometimes towards susceptibility, depending on the inoculation conditions. AvrLmS-Lep2 was nevertheless sufficient to significantly slow the systemic growth of the pathogen and reduce the stem lesion size on plant genotypes with LepR2, indicating the potential efficiency of this resistance to control the disease in the field.

High amounts of medium-chain-length polyhydroxyalkanoates subunits can be accumulated in recombinant Cupriavidus necator with wild-type synthase

Recombinant Cupriavidus necator H16/pMPJAS03, expressing a P. putida KT2440 enoyl-CoA hydratase (phaJ), was able to synthesize short-chain-length/ medium-chain-length (scl-mcl) PHA copolymers with a high content of mcl subunits using its native poly(3-hydroxyalkanoate) synthase. The cells were cultivated on fructose with canola oil or canola oil/decanoic acid (DA) mixtures in fed-batch fermentations. The recombinant C. necator H16 (without any synthase modification) produced a polymer composed of 3-hydroxybutyrate (3HB) with mcl-subunits, including 3-hydroxyhexanoate (3HHx), and about 300-fold more 3-hydroxyoctanoate (3HO) than the yields reported in previous studies, as well as a significant amount of 3-hydroxydecanoate (3HD). Increasing the DA content in the feed from 0 to 15% v/v increased the molar content of the 3HD subunits from 1.2 to 2.1mol%. The presence of larger monomers, such as 3HO and 3HD, decreased the crystallinity and melting temperature and modified the mechanical properties of the polymers. Thus, replacing either of the two gene products (phaJ or phaC1) required to produce PHA from CoA-3-hydroxy fatty acids with broader spectrum enzymes, is suitable for the production of commercially useful scl-mcl-PHA.

Control Strategies of Clubroot Disease Caused by Plasmodiophora brassicae

The clubroot disease caused by the soil-borne pathogen Plasmodiophora brassicae is one of the most important diseases of cruciferous crops worldwide. As with many plant pathogens, the spread is closely related to the cultivation of suitable host plants. In addition, temperature and water availability are crucial determinants for the occurrence and reproduction of clubroot disease. Current global changes are contributing to the widespread incidence of clubroot disease. On the one hand, global trade and high prices are leading to an increase in the cultivation of the host plant rapeseed worldwide. On the other hand, climate change is improving the living conditions of the pathogen P. brassicae in temperate climates and leading to its increased occurrence. Well-known ways to control efficiently this disease include arable farming strategies: growing host plants in wide crop rotations, liming the contaminated soils, and using resistant host plants. Since chemical control of the clubroot disease is not possible or not ecologically compatible, more and more alternative control options are being investigated. In this review, we address the challenges for its control, with a focus on biological control options.

Long-Term Persistence of Arbuscular Mycorrhizal Fungi in the Rhizosphere and Bulk Soils of Non-host Brassica napus and Their Networks of Co-occurring Microbes

Arbuscular mycorrhizal fungi (AMF) are obligate plant symbionts that improve the nutrition and health of their host. Most, but not all the crops form a symbiosis with AMF. It is the case for canola (Brassica napus), an important crop in the Canadian Prairies that is known to not form this association. From 2008 to 2018, an experiment was replicated at three locations of the Canadian Prairies and it was used to assess the impact of canola on the community of AMF naturally occurring in three cropping systems, canola monoculture, or canola in two different rotation systems (2-years, canola-wheat and 3-years, barley-pea-canola). We sampled canola rhizosphere and bulk soils to: (i) determine diversity and community structure of AMF, we expected that canola will negatively impact AMF communities in function of its frequency in crop rotations and (ii) wanted to assess how these AMF communities interact with other fungi and bacteria. We detected 49 AMF amplicon sequence variants (ASVs) in canola rhizosphere and bulk soils, confirming the persistence of a diversified AMF community in canola-planted soil, even after 10 years of canola monoculture, which was unexpected considering that canola is among non-mycorrhizal plants. Network analysis revealed a broad range of potential interactions between canola-associated AMF and some fungal and bacterial taxa. We report for the first time that two AMF, Funneliformis mosseae and Rhizophagus iranicus, shared their bacterial cohort almost entirely in bulk soil. Our results suggest the existence of non-species-specific AMF-bacteria or AMF-fungi relationships that could benefit AMF in absence of host plants. The persistence of an AMF community in canola rhizosphere and bulk soils brings a new light on AMF ecology and leads to new perspectives for further studies about AMF and soil microbes interactions and AMF subsistence without mycotrophic host plants.

Identification of Arabidopsis Phospholipase A Mutants With Increased Susceptibility to Plasmodiophora brassicae

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is one of the most devastating diseases of canola (Brassica napus) in Canada. The identification of novel genes that contribute to clubroot resistance is important for the sustainable management of clubroot, as these genes may be used in the development of resistant canola cultivars. Phospholipase As (PLAs) play important roles in plant defense signaling and stress tolerance, and thus are attractive targets for crop breeding. However, since canola is an allopolyploid and has multiple copies of each PLA gene, it is time-consuming to test the functions of PLAs directly in this crop. In contrast, the model plant Arabidopsis thaliana has a simpler genetic background and only one copy of each PLA. Therefore, it would be reasonable and faster to validate the potential utility of PLA genes in Arabidopsis first. In this study, we identified seven homozygous atpla knockout/knockdown mutants of Arabidopsis, and tested their performance following inoculation with P. brassicae. Four mutants (pla₁-iiα, pla₁-iγ3, pla₁-iii, ppla-iiiβ, ppla-iiiδ) developed more severe clubroot than the wild-type, suggesting increased susceptibility to P. brassicae. The homologs of these Arabidopsis PLAs (AtPLAs) in B. napus (BnPLAs) were identified through Blast searches and phylogenic analysis. Expression of the BnPLAs was subsequently examined in transcriptomic datasets generated from canola infected by P. brassicae, and promising candidates for further characterization identified.

Gene expression profiling reveals transcription factor networks and subgenome bias during Brassica napus seed development

We profiled the global gene expression landscape across the reproductive lifecycle of Brassica napus. Comparative analysis of this nascent amphidiploid revealed the contribution of each subgenome to plant reproduction. Whole-genome transcription factor networks identified BZIP11 as a transcriptional regulator of early B. napus seed development. Knockdown of BZIP11 using RNA interference resulted in a similar reduction in gene activity of predicted gene targets, and a reproductive-lethal phenotype. Global mRNA profiling revealed lower accumulation of Cⁿ subgenome transcripts relative to the Aⁿ subgenome. Subgenome-specific transcription factor networks identified distinct transcription factor families enriched in each of the Aⁿ and Cⁿ subgenomes early in seed development. Analysis of laser-microdissected seed subregions further reveal subgenome expression dynamics in the embryo, endosperm and seed coat of early stage seeds. Transcription factors predicted to be regulators encoded by the Aⁿ subgenome are expressed primarily in the seed coat, whereas regulators encoded by the Cⁿ subgenome were expressed primarily in the embryo. Data suggest subgenome bias are characteristic features of the B. napus seed throughout development, and that such bias might not be universal across the embryo, endosperm and seed coat of the developing seed. Transcriptional networks spanning both the Aⁿ and Cⁿ genomes of the whole B. napus seed can identify valuable targets for seed development research and that -omics level approaches to studying gene regulation in B. napus can benefit from both broad and high-resolution analyses.

Increasing the Efficiency of Canola and Soybean GMO Detection and Quantification Using Multiplex Droplet Digital PCR

Simple Summary

Digital PCR (dPCR) technology has been used for absolute quantification of genetically modified (GM) events. Duplex dPCR consisting of a target gene and a reference gene is mostly used for absolute quantification of GM events. We investigated the feasibility of absolute quantification of two, three, and four GM canola and soybean events at the same time using the QX200 Droplet Digital PCR (ddPCR) system. Adjustments of the probe concentrations and labels for some of the assays were needed for successful multiplex ddPCR. Absolute quantification of GM canola and soybean events was achieved for duplex, triplex, and tetraplex ddPCR at 0.1%, 1%, and 5% concentrations.

Abstract

The number of genetically modified (GM) events for canola, maize, and soybean has been steadily increasing. Real-time PCR is widely used for the detection and quantification of individual GM events. Digital PCR (dPCR) has also been used for absolute quantification of GM events. A duplex dPCR assay consisting of one reference gene and one GM event has been carried out in most cases. The detection of more than one GM event in a single assay will increase the efficiency of dPCR. The feasibility of detection and quantification of two, three, and four GM canola and soybean events at the same time was investigated at 0.1%, 1%, and 5% levels using the QX200 Droplet Digital PCR (ddPCR) system. The reference gene assay was carried out on the same plate but in different wells. For some of the assays, optimization of the probe concentrations and labels was needed for successful ddPCR. Results close to the expected result were achieved for duplex, triplex, and tetraplex ddPCR assays for GM canola events. Similar ddPCR results were also achieved for some GM soybean events with some exceptions. Overall, absolute quantification of up to four GM events at the same time improves the efficiency of GM detection.

Hard to Kill: Inactivation of Plasmodiophora brassicae Resting Spores Using Chemical Disinfectants

Biosafety practices, such as bioexclusion via sanitization, can prevent the spread of infectious soilborne threats such as the clubroot pathogen Plasmodiophora brassicae. Twenty-three chemical disinfectants were evaluated for efficacy against P. brassicae resting spores. Evans blue staining was used to directly measure the viability of P. brassicae resting spores after 20-min exposures to 10 concentrations of each of the 23 chemical disinfectants. Only nine disinfectants were capable of >95% inactivation, and only five were capable of inactivating >99% of resting spores. Bleach (sodium hypochlorite) and Spray Nine were the most effective disinfectants for inactivation of clubroot resting spores. AES 2500, SaniDate, and ethanol also inactivated >99% of resting spores but only at very high concentrations. A time course experiment showed that 10- to 12-min contact time was sufficient for ≥95% resting spore inactivation with Spray Nine and sodium hypochlorite, but ≥30-min contact was required for other disinfectants evaluated. These results will assist in guiding management recommendations for sanitization aimed at bioexclusion and biocontainment of P. brassicae.

Hybrid Canola under Varying Nitrogen Availabilities

Improving nitrogen use efficiency (NUE) is essential for sustainable agriculture, especially in high-N-demanding crops such as canola (Brassica napus). While advancements in above-ground agronomic practices have improved NUE, research on soil and below-ground processes are limited. Plant NUE-and its components, N uptake efficiency (NUpE), and N utilization efficiency (NUtE)-can be further improved by exploring crop variety and soil N cycling. Canola parental genotypes (NAM-0 and NAM-17) and hybrids (H151857 and H151816) were grown on a dark brown chernozem in Saskatchewan, Canada. Soil and plant samples were collected at the 5-6 leaf stage and flowering, and seeds were collected at harvest maturity. Soil N cycling varied with phenotypic stage, with higher potential ammonium oxidation rates at the 5-6 leaf stage and higher urease activity at flowering. Seed N uptake was higher under higher urea-N rates, while the converse was true for NUE metrics. Hybrids had higher yield, seed N uptake, NUtE, and NUE, with higher NUE potentially owing to higher NUtE at flowering, which led to higher yield and seed N allocation. Soil N cycling and soil N concentrations correlated for improved canola NUE, revealing below-ground breeding targets. Future studies should consider multiple root characteristics, including rhizosphere microbial N cycling, root exudates, and root system architecture, to determine the below-ground dynamics of plant NUE.