Salicylic acid (SA) is a key regulator of plant immunity and contributes to defence against Plasmodiophora brassicae, the causal agent of clubroot disease in canola (Brassica napus) and other crucifers. Exogenous SA applications have reduced clubroot severity in some Brassica pathosystems, yet the effectiveness of foliar SA treatment against the predominant resistance-breaking pathotype 3A in western Canada remains unclear. This study evaluated the effects of weekly foliar applications of 0, 1, 5, or 10 mM SA on clubroot development in two B. napus var. napobrassica cultivars under greenhouse and growth chamber conditions. Plants inoculated with pathotype 3A were assessed for disease severity, pathogen resting spore load, plant height, and transcript accumulation of SA-responsive genes. Overall, SA treatments resulted in modest reductions in disease severity and resting spore concentrations; however, treatment effects did not reach statistical significance in most cases. Collectively, foliar SA applications provided limited suppression of clubroot caused by pathotype 3A. Further optimization of SA concentration, timing, and delivery, particularly when targeting the root zone, may be required before SA can be considered a complementary tool in integrated clubroot management.

Stripe rust of wheat, caused by Puccinia striiformis f. sp. tritici (Pst) remains a major threat to global wheat production. In Canada, long-term collection of Pst isolates since 1984 provides a unique perspective on pathogen evolution over four decades. This study extends previous race structure analyses by characterizing 73 isolates collected since 2020 from wheat, barley, and wild barley. Among 56 wheat-infecting isolates, 23 races were identified, including 16 new races (C90 to C105). The predominant races C17 and C43 and the newly emerged C96 accounted for 50% of isolates, with C96 likely evolving stepwise from C43 through acquisition of virulence to cultivar Tyee ( YrTye); this cultivar was resistant in previous years. Alberta remains a hotspot of Pst diversity (14 races), whereas Saskatchewan showed lower diversity (5 races). Most isolates were virulent to Yr6, Yr7, Yr8, Yr9, Yr17, Yr27, Yr43, Yr44, YrTr1, and YrExp2, whereas Yr5 and Yr15 remained undefeated; Yr1, Yr10, Yr24, Yr32, and YrSP conferred resistance to most of the isolates. Cultivated barley-derived isolates infected both wheat and barley and displayed distinct virulence profiles, suggesting interspecific adaptation and possible hybridization with P. striiformis f. sp. hordei (Psh). Additionally, analysis of the Cyp51 gene revealed the presence of a nonsynonymous mutation Y134F in one Psh isolate but its absence across tested Pst populations over the past 40 years in Canada, signifying potential evolution of fungicide tolerance or fitness adaptation in barley-infecting form.

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is a soilborne disease affecting canola (Brassica napus) and other crucifers. Although planting resistant cultivars remains the primary strategy for managing clubroot, the emergence of resistance-breaking P. brassicae pathotypes continues to threaten canola production. In this context, soil and root microorganisms may play a role in suppressing the disease. This study investigated the impact of P. brassicae infection on the microbial communities of soil, seeds, roots, and the rhizosphere in susceptible and resistant canola lines, with the aim of analyzing host–pathogen–microbiome interactions and identifying microbial taxa potentially associated with disease resistance. Our findings showed that resistant canola lines inoculated with P. brassicae (pathotype 3A) exhibited reduced disease severity compared to their susceptible counterparts. Diversity analyses of microbial communities revealed that clubroot-resistant canola lines tended to maintain more stable and diverse fungal communities, with a higher Shannon index than susceptible lines. Inoculation with P. brassicae induced more pronounced changes in the root microbiome than in the rhizosphere. Additionally, the seed microbiomes of resistant and susceptible lines displayed distinct bacterial and fungal profiles, suggesting that clubroot susceptibility may influence seed-associated microbial community composition. Differential abundance analysis of root and rhizosphere microbiomes indicated that certain microbial taxa, including bacterial genera such as Acidovorax, Bacillus, Cupriavidus, Cytophaga, Duganella, Flavobacterium, Fluviicola, Luteimonas, Methylotenera, Pedobacter, and Peredibacter, as well as fungal genera such as Aspergillus, Candida, Fusicolla, Paecilomyces, and Rhizophlyctis, may be recruited or enriched in resistant canola lines following P. brassicae inoculation, potentially contributing to reduced clubroot severity.

Clubroot, a soilborne disease caused by Plasmodiophora brassicae, poses a significant threat to canola (Brassica napus) production. The use of lime to elevate soil pH shows promise for clubroot management. In this study, limestone and hydrated lime (HL) were evaluated for their effectiveness in controlling clubroot across four field sites in 2019 to 2020 and 2021 to 2022, and in greenhouse trials conducted in 2019 to 2020 and 2020 to 2021. The treatments included an untreated control (UTC), limestone applied at rates of 5 and 10 t ha −1 in either fall or spring, spring application of HL at 5.0 and 10 t ha −1 , and a combination of fall limestone application with spring HL application at rates of 2.5 or 5.0 t ha −1 each. The canola hybrids ‘45H31’ (susceptible) and ‘CS2000’ (moderately resistant) were included in the greenhouse experiments, while ‘45H31’ was used in the field. Significant reductions (P < 0.05) in clubroot severity relative to the UTCs were observed in all lime treatments in the field or greenhouse, except for the 5.0 t ha −1 spring limestone application at one field site in 2021 to 2022. Increases in soil pH and reductions in soil inoculum density were recorded for all lime treatments. The most consistent reductions in clubroot severity across sites and years were obtained with fall limestone or spring HL application at 10 t ha −1 , or the combination of fall limestone and spring HL at 5 t ha −1 each. Applying limestone in the fall may present a viable option for managing clubroot in canola. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Clubroot disease, caused by Plasmodiophora brassicae, is a major threat to canola (Brassica napus) production in the Canadian Prairies. One of the most effective clubroot management strategies is the deployment of clubroot-resistant cultivars. 'First-generation' resistant cultivars, with resistance derived from B. napus cv. 'Mendel', provided farmers with an initial line of defence. However, the emergence of more virulent pathotypes of P. brassicae has led to an increasing number of cases where these novel pathotypes overcome resistance, resulting in severe clubroot symptoms in previously resistant cultivars. In this study, 206 field isolates of the pathogen were collected between 2021 and 2023 from Alberta (194 isolates), Saskatchewan (eight isolates) and Manitoba (four isolates). Pathotype designations were determined using the Canadian Clubroot Differential (CCD) set, leading to the identification of 31 unique pathotypes. Among these were 10 novel 'resistance-breaking' pathotypes, designated as 1D, 1E, 1G, 3F, 3I, 3J, 5D, 6F, 8K and 9G, along with pathotypes 1H and 3G, still controlled by first-generation resistance. The novel pathotype 5D, virulent on 'Mendel', represents the first instance of a resistance-breaking pathotype in Saskatchewan. Despite the large number of pathotypes detected, pathotypes 3A (25%), 3D (17%) and 3H (15%) remain the most prevalent in Alberta, consistent with previous years. Other notable pathotypes, including 8E, 8N, 8P and 9E, continue to be detected, albeit at lower frequencies (4-8%). The rapid diversification of pathotypes and the spread of P. brassicae in the canola growing regions of Canada underscore the importance of continued surveillance.

Understanding the molecular mechanisms used by phytophagous insects to survive and feed on new hosts is key to explaining their mechanisms of range expansion and diversification. However, only a few Neotropical biological models have been used to understand these mechanisms. In this study, we investigated the differences in gene expression of the Neotropical phytophagous insect Anastrepha obliqua Macquart (Diptera: Tephritidae), the West Indian Fruit Fly, when feeding on three different host plant species under sympatric and synchronous conditions. Third‐instar larvae of A. obliqua infesting red mombin ( Spondias purpurea L.), mango ( Mangifera indica L.), and carambola ( Averrhoa carambola L.) were collected in two localities in southwestern Colombia. After assembling a de novo transcriptome, differences in gene expression between larvae infesting the three host species were established using a batch effect design, controlling the variability introduced by location. Sixty‐four differentially expressed unigenes were identified among flies infesting the different hosts, with the greatest number of genes differentially expressed between red mombin and carambola. Digestive genes, such as alpha‐amylases and serine proteases, were upregulated in larvae from red mombin compared with mango (six genes) and carambola (four genes), suggesting the response of A. obliqua to the nutritional composition in red mombin. Also, two genes related to immune system responses, glutactin and acidic phospholipase A2, were upregulated in mango compared to carambola. Notably, genes annotated as transposable elements (TEs) were consistently upregulated in larvae infesting carambola and mango compared to larvae infesting red mombin. This may suggest the activation of these TEs in acclimation or adaptation to new hosts. Based on our results, the main categories of differentially expressed genes in A. obliqua were serine proteases, detoxification proteins, and proteins associated with the regulation of gene expression. These results support the potential of A. obliqua to adapt to host plants and its qualification as a generalist species.

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is a serious soilborne disease that threatens many commercially valuable crops in the Brassicaceae family, including the oilseed crop canola (Brassica napus) and various vegetables. Evidence from studies analyzing hormonal profiles, transcriptomes, proteomes, mutants defective in hormone functions, and treatments of infected plants with growth regulators suggest that nearly all plant hormones are involved in or affected by the disease. However, the specific roles of individual hormones in clubroot development or resistance remain unclear. This knowledge gap is compounded by the complex regulation of hormone functions and inconsistencies across studies, likely due to variations caused by host–pathogen combinations and other factors such as environmental influences. Additionally, biotic and abiotic stress responses caused by the disease and, in some instances, pathogen proteins manipulating host hormonal metabolism add additional layers of complexity. Despite these challenges, emerging trends suggest regulatory roles for plant hormones in both disease development and host defense. In this review, we explore these patterns, aiming to elucidate the contributions of different hormones to clubroot development and associated stress responses.

In this study, a rutabaga (Brassica napus ssp. napobrassica) donor parent FGRA106, which exhibited broad-spectrum resistance to 17 isolates representing 16 pathotypes of Plasmodiophora brassicae, was used in genetic crosses with the susceptible spring-type canola (B. napus ssp. napus) accession FG769. The F2 plants derived from a clubroot-resistant F1 plant were screened against three P. brassicae isolates representing pathotypes 3A, 3D, and 3H. Chi-square (χ2) goodness-of-fit tests indicated that the F2 plants inherited two major clubroot resistance genes from the CR donor FGRA106. The total RNA from plants resistant (R) and susceptible (S) to each pathotype were pooled and subjected to bulked segregant RNA-sequencing (BSR-Seq). The analysis of gene expression profiles identified 431, 67, and 98 differentially expressed genes (DEGs) between the R and S bulks. The variant calling method indicated a total of 12 (7 major + 5 minor) QTLs across seven chromosomes. The seven major QTLs included: BnaA5P3A.CRX1.1, BnaC1P3H.CRX1.2, and BnaC7P3A.CRX1.1 on chromosomes A05, C01, and C07, respectively; and BnaA8P3D.CRX1.1, BnaA8P3D.RCr91.2/BnaA8P3H.RCr91.2, BnaA8P3H.Crr11.3/BnaA8P3D.Crr11.3, and BnaA8P3D.qBrCR381.4 on chromosome A08. A total of 16 of the DEGs were located in the major QTL regions, 13 of which were on chromosome C07. The molecular data suggested that clubroot resistance in FGRA106 may be controlled by major and minor genes on both the A and C genomes, which are deployed in different combinations to confer resistance to the different isolates. This study provides valuable germplasm for the breeding of clubroot-resistant B. napus cultivars in Western Canada.

Spatial variability in soil pH is a major contributor to within-field variations in soil fertility and crop productivity. An improved understanding of the spatial variability of soil pH within agricultural fields is required to determine liming requirements for precision farming. This study with the use of proximal sensors, firstly assessed the spatial pattern of soil pH and how it can be used to determine site-specific, spatially variable lime requirements. Secondly, the effects of soil pH on soil concentrations of nitrate nitrogen (N0(3)-N), phosphorus (P), potassium (K), sulfur (SO4-S), calcium (Ca), magnesium (Mg), soil organic matter (SOM), aluminum (Al), and manganese (Mn) were assessed in three study fields in central Alberta, Canada. Soil pH varied between 4.5 and 7.5 across all field sites. The field-scale coefficient of variation (CV %) for soil pH, Al and Mn ranged between 4.39 and 7.50 %, 7.33-13.72 %, and 7.33-13.72 % across the three sites. The other soil properties showed low, moderate, and high variability, with field-scale CVs ranging between 6.39 and 17.70 % for SOM and 24.33-91.39 % for SO4-S. Soil pH exhibited positive correlations with both Ca and Mg, across all fields. Negative correlations were observed between soil pH and Al across all fields. A principal component analysis (PCA) was performed for all soil parameters and two principal components accounted for 50%, 54.9%, and 76.8% of the total variance in field 1, field 2, and field 3, respectively. Geostatistical semivariance indicated a strong spatial dependence of all chemical parameters across fields. Large regions within a field were strongly acidic (pH < 5.5) and required lime applications ranging from 0 to 6 t ha(-1). We conclude that proximal soil sensors can be calibrated to soil properties, enabling variable rate lime recommendations on spatially variable fields for the management of soil acidity.

Verticillium stripe, caused by Verticillium longisporum, is an emerging disease of canola (Brassica napus) in Canada. Studies were conducted to assess the impact of pH on both the growth of V. longisporum and its virulence on the canola host. Fungal growth was assessed by measuring the colony diameter following 14 and 21 days of incubation on potato dextrose agar at varying pH levels (4.7, 5.5, 6.5, 7.4, or 8.6). The results indicated that colonies of V. longisporum were approximately 16% greater in diameter at pH 7.4 and 8.6 compared with those at pH 5.5. The impact of pH on disease development at the seedling stage was investigated using a semi-hydroponic system with different pH levels of 4.4, 5.4, 6.3, 7.5, and 8.4 in half-strength Hoagland’s solution. Verticillium stripe was most severe at pH 7.5 and 8.4 after a 10-day period in the semi-hydroponic system. In a second inoculation experiment, canola seedlings previously inoculated with the fungus were transplanted into potting mix amended to four pH levels (5.6, 6.4, 7.2, and 7.8). The transplants were cultivated under greenhouse conditions and evaluated for Verticillium stripe severity at plant maturity. Disease severity was greatest at pH 7.8. This is the first study on the effects of pH on V. longisporum in canola. It suggests a substantial risk of increased disease severity and yield losses due to Verticillium stripe in regions with neutral to slightly alkaline soils.

Clubroot is a soilborne disease of canola (Brassica napus) and other crucifers caused by the obligate parasite Plasmodiophora brassicae. In western Canada, clubroot is usually managed by planting-resistant cultivars, but the emergence of resistance-breaking pathotypes of P. brassicae represents a major threat to sustainable canola production. The rhizosphere and root contain beneficial microorganisms that can improve plant health. In this study, we evaluated the effect of two P. brassicae isolates (termed A and B) with different levels of virulence on the root and rhizosphere microbiomes of clubroot-resistant and clubroot-susceptible canola. Additionally, potential biocontrol microorganisms were identified based on taxa antagonistic to clubroot. Although both P. brassicae isolates were classified as pathotype 3A, isolate A caused a higher disease severity index in the resistant canola genotype compared with isolate B. Metabarcoding analysis indicated a shift in the bacterial and fungal communities in response to inoculation with either field isolate. Root endophytic bacterial and fungal communities responded to changes in inoculation, isolate type, sampling time, and canola genotype. In contrast, fungal communities associated with the rhizosphere exhibited significant differences between sampling times, while bacterial communities associated with the rhizosphere exhibited low variability.

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is one of the most devastating diseases affecting the canola/oilseed rape (Brassica napus) industry worldwide. Currently, the planting of clubroot-resistant (CR) cultivars is the most effective strategy used to restrict the spread and the economic losses linked to the disease. However, virulent P. brassicae isolates have been able to infect many of the currently available CR cultivars, and the options to manage the disease are becoming limited. Another challenge has been achieving consistency in evaluating host reactions to P. brassicae infection, with most bioassays conducted in soil and/or potting medium, which requires significant space and can be labor intensive. Visual scoring of clubroot symptom development can also be influenced by user bias. Here, we have developed a hydroponic bioassay using well-characterized P. brassicae single-spore isolates representative of clubroot virulence in Canada, as well as field isolates from three Canadian provinces in combination with canola inbred homozygous lines carrying resistance genetics representative of CR cultivars available to growers in Canada. To improve the efficiency and consistency of disease assessment, symptom severity scores were compared with clubroot evaluations based on the scanned root area. According to the results, this bioassay offers a reliable, less expensive, and reproducible option to evaluate P. brassicae virulence, as well as to identify which canola resistance profile(s) may be effective against particular isolates. This bioassay will contribute to the breeding of new CR canola cultivars and the identification of virulence genes in P. brassicae that could trigger resistance and that have been very elusive to this day. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Root rot disease poses a significant threat to canola (Brassica napus), underscoring the need for a comprehensive understanding of its causal agents for more effective disease mitigation. The composition and diversity of fungal pathogens associated with root rot of canola in Alberta, Canada, were evaluated from plant tissue samples collected in 2021 and 2022. The study revealed Fusarium spp. as the predominant pathogens found in almost all surveyed fields. Fusarium avenaceum, F. redolens, and F. solani were among the most frequently recovered species. Greenhouse trials confirmed their pathogenicity, with F. avenaceum and F. sporotrichioides found to be particularly aggressive. Additionally, F. sporotrichioides and F. commune were identified for the first time as canola root rot pathogens. Inoculation with isolates of most species resulted in significant reductions in seedling emergence, plant height, and shoot and root dry weights. Analysis of translation elongation factor 1-α (TEF-1α) and internal transcribed spacer (ITS) sequences confirmed the identity of the Fusarium spp., while concatenating the ITS and TEF-1α sequences enabled improved species differentiation. Geographic and year effects did not influence fungal diversity or aggressiveness, as determined by principal component analysis. This study emphasized the high diversity and impact of Fusarium spp. in causing canola root rot.

The sustainable cultivation of canola is under threat from clubroot disease (Plasmodiophora brassicae). The pathogen’s resting spores can survive in the soil for extended periods, complicating disease management. Therefore, effective clubroot control requires a combination of tactics that provide multiple layers of protection. Management strategies have focused on pathogen avoidance and reducing disease levels in infested fields. The sanitation of machinery and field equipment remains the most effective method for preventing the pathogen’s introduction into non-infested fields. For disease reduction, crop rotation, liming, chemical control, and host resistance are commonly employed, with the use of clubroot-resistant cultivars being the most effective to date. However, resistance breakdown has been observed within four years of the introduction of new cultivars, jeopardizing the long-term effectiveness of this approach. A promising yet underexplored strategy is the use of cultivar mixtures. This approach leverages mechanisms such as the dilution effect, the barrier effect, induced resistance, disruptive selection, and the compensatory effect to control the disease. Cultivar mixtures have the potential to reduce the impact of clubroot on canola production while preserving pathogen population structure, thereby minimizing the likelihood of resistance breakdown. Given its potential, further research into cultivar mixtures as a management strategy for clubroot disease is warranted.

Fusarium spp. are commonly associated with the root rot complex of soybean (Glycine max). Previous surveys identified six common Fusarium species from Manitoba, including F. oxysporum, F. redolens, F. graminearum, F. solani, F. avenaceum, and F. acuminatum. This study aimed to determine their pathogenicity, assess host resistance, and evaluate the genetic diversity of Fusarium spp. isolated from Canada. The pathogenicity of these species was tested on two soybean cultivars, ‘Akras’ (moderately resistant) and ‘B150Y1′ (susceptible), under greenhouse conditions. The aggressiveness of the fungal isolates varied, with root rot severities ranging from 1.5 to 3.3 on a 0–4 scale. Subsequently, the six species were used to screen a panel of 20 Canadian soybean cultivars for resistance in a greenhouse. Cluster and principal component analyses were conducted based on the same traits used in the pathogenicity study. Two cultivars, ‘P15T46R2′ and ‘B150Y1′, were consistently found to be tolerant to F. oxysporum, F. redolens, F. graminearum, and F. solani. To investigate the incidence and prevalence of Fusarium spp. in Canada, fungi were isolated from 106 soybean fields surveyed across Manitoba, Saskatchewan, Ontario, and Quebec. Eighty-three Fusarium isolates were evaluated based on morphology and with multiple PCR primers, and phylogenetic analyses indicated their diversity across the major soybean production regions of Canada. Overall, this study contributes valuable insights into host resistance and the pathogenicity and genetic diversity of Fusarium spp. in Canadian soybean fields.

Verticillium stripe, caused by Verticillium longisporum, presents an emerging threat to Canadian canola (Brassica napus). Initially detected in Manitoba in 2014, the presence of this pathogen has since been confirmed across western Canada. Infections by V. longisporum can result in yield losses of up to 50%, which is a cause for concern given the susceptibility of most commercial Canadian canola cultivars. The objective of this study was to screen a collection of 211 Brassica genotypes for their reactions to V. longisporum, and to use genome-wide association study (GWAS) to identify single nucleotide polymorphism (SNP) markers for resistance. The plant material consisted of 110 rutabaga (B. napus ssp. napobrassica), 35 canola, 40 Brassica rapa, and 15 Brassica oleracea accessions or cultivars, alongside 11 hosts of the European Clubroot Differential (ECD) set. These materials were screened for resistance under greenhouse conditions and were genotyped using a 19K Brassica SNP array. Three general linear models (GLM), four mixed linear models (MLM), and three GWAS methods were employed to evaluate the markers. Eleven non-commercial Brassica accessions and 9 out of 35 commercial canola cultivars displayed a low normalized area under the disease progress curve (AUDPCnorm.). The non-commercial accessions could prove valuable as potential sources of resistance against V. longisporum. Forty-five SNP markers were identified to be significantly associated with V. longisporum resistance using single-SNP based GWAS analysis. In comparison, haplotype-based GWAS analyses identified 10 to 25 haplotype blocks to be significantly associated with V. longisporum resistance. Between 20% and 56% of QTLs identified by the more conventional single-SNP based GWAS analysis were also detected by the haplotype-based GWAS analysis. The overlapping genomic regions identified by the two GWAS methods present promising hotspots for marker-assisted selection in the future development of Verticillium stripe-resistant canola.

Abstract Tan spot is a globally distributed disease caused by the necrotrophic fungus Pyrenophora tritici-repentis . It infects both durum and common wheat, leading to significant yield losses under conditions conducive to disease development. The fungus has a wide host range among grass species and can survive on alternative hosts, crop debris, and infected seeds. Management of tan spot involves several practices, including burning or burying crop debris from previous seasons, rotating crops with non-cereal species, and using non-infected seeds. While several fungicides are available for tan spot control, their use can be costly and raise environmental concerns. Although some common wheat varieties show limited resistance, very few durum wheat genotypes exhibit this trait. Efforts to breed for tan spot resistance have been both scant and largely unsuccessful. The lack of an effective differential set for identifying races of P. tritici-repentis from durum wheat, along with insufficient understanding of the host-pathogen interaction, has hindered breeding efforts and delayed the development of resistant varieties. This plant health case offers an overview of P. tritici-repentis , including its life cycle and genetic diversity. It also discusses the historical development and opportunities for improving the race classification system, along with the achievements and challenges associated with tan spot management. Information © The Authors 2024

The root systems of Brassica species are complex. Eight root system architecture (RSA) traits, including total root length, total root surface area, root average diameter, number of tips, total primary root length, total lateral root length, total tertiary root length, and basal link length, were phenotyped across 379 accessions representing six Brassica species (B. napus, B. juncea, B. carinata, B. oleracea, B. nigra, and B. rapa) using a semi-hydroponic system and image analysis software. The results suggest that, among the assessed species, B. napus and B. oleracea had the most intricate and largest root systems, while B. nigra exhibited the smallest roots. The two species B. juncea and B. carinata shared comparable root system complexity and had root systems with larger root diameters. In addition, 313 of the Brassica accessions were genotyped using a 19K Brassica single nucleotide polymorphism (SNP) array. After filtering by TASSEL 5.0, 6,213 SNP markers, comprising 5,103 markers on the A-genome (covering 302,504 kb) and 1,110 markers on the C-genome (covering 452,764 kb), were selected for genome-wide association studies (GWAS). Two general linear models were tested to identify the genomic regions and SNPs associated with the RSA traits. GWAS identified 79 significant SNP markers associated with the eight RSA traits investigated. These markers were distributed across the 18 chromosomes of B. napus, except for chromosome C06. Sixty-five markers were located on the A-genome, and 14 on the C-genome. Furthermore, the major marker-trait associations (MTAs)/quantitative trait loci (QTLs) associated with root traits were located on chromosomes A02, A03, and A06. Brassica accessions with distinct RSA traits were identified, which could hold functional, adaptive, evolutionary, environmental, pathological, and breeding significance.

A semi-hydroponic system was developed to assess canola ( Brassica napus L.) root architectural traits. Four cultivars were grown under controlled conditions in germination paper rolls immersed in half-strength Hoagland’s solution. Eight parameters, including total root length, total root surface area, average root diameter, tip number, total primary root length, total lateral root length, total tertiary root length, and basal link length, were analyzed using the WinRHIZO software after 7, 14, and 21 days. The results suggested that 14 days in the semi-hydroponic system were optimal for accurate root trait assessment, as clear differences were observed while maintaining ease of handling and scanning.

The soil-borne pathogen Plasmodiophora brassicae is the causal agent of clubroot, a major disease in Chinese cabbage (Brassica rapa ssp. pekinensis). The host’s resistance genes often confer immunity to only specific pathotypes and may be rapidly overcome. Identification of novel clubroot resistance (CR) from germplasm sources is necessary. In this study, Bap246 was tested by being crossed with different highly susceptible B. rapa materials and showed recessive resistance to clubroot. An F2 population derived from Bap246 × Bac1344 was used to locate the resistance Quantitative Trait Loci (QTL) by Bulk Segregant Analysis Sequencing (BSA-Seq) and QTL mapping methods. Two QTL on chromosomes A01 (4.67–6.06 Mb) and A08 (10.42–11.43 Mb) were found and named Cr4Ba1.1 and Cr4Ba8.1, respectively. Fifteen and eleven SNP/InDel markers were used to narrow the target regions in the larger F2 population to 4.67–5.17 Mb (A01) and 10.70–10.84 Mb (A08), with 85 and 19 candidate genes, respectively. The phenotypic variation explained (PVE) of the two QTL were 30.97% and 8.65%, respectively. Combined with gene annotation, mutation site analysis, and real-time quantitative polymerase chain reaction (qRT-PCR) analysis, one candidate gene in A08 was identified, namely Bra020861. And an insertion and deletion (InDel) marker (co-segregated) named Crr1-196 was developed based on the gene sequence. Bra013275, Bra013299, Bra013336, Bra013339, Bra013341, and Bra013357 in A01 were the candidate genes that may confer clubroot resistance in Chinese cabbage. The resistance resource and the developed marker will be helpful in Brassica breeding programs.