Canola Blackleg Fungus Genome Sequenced, Revealing Candidate Virulence Genes

Researchers have sequenced and assembled the whole genome of Plenodomus biglobosus, the fungus behind blackleg disease in Brassica crops, and used comparative genomics to flag genes that may underpin its ability to attack plants. The team sequenced the nm-1 strain, isolated from a canola-producing region in Hailar, Inner Mongolia, using PacBio long-read sequencing, and reported the results in BMC Genomics. Blackleg caused by this pathogen reduces both yield and crop quality in Brassica species and can cross-infect other cruciferous vegetables, making the genomic blueprint a reference point for understanding how the fungus invades host tissue.

The assembled genome of the nm-1 strain totals 33.18 megabases, distributed across 35 scaffolds, and contains 9,002 predicted protein-coding genes with a GC content of 49.56 percent. Functional annotation of that sequence revealed 1,387 carbohydrate-active enzymes, the enzymatic toolkit fungi use to dismantle plant cell walls. Within this repertoire, 526 glycoside hydrolases stood out, a class of enzymes that plays key roles in cellulose degradation.

To place these enzymes in a pathological context, the researchers screened the genome against the Pathogen-Host Interaction Database. This analysis identified several genes with known or putative roles in pathogenicity, providing a shortlist of candidates for future functional studies. The authors emphasize that these are candidate genes potentially involved in pathogenicity, identified through sequence-based inference rather than direct experimental demonstration of virulence functions in the nm-1 strain.

The comparative component of the study widened the lens to four related plant pathogens in the genus Plenodomus: P. biglobosus, P. lingam, the causal agent of canola stem base ulcer; P. lindquistii, which causes sunflower blackleg; and P. tracheiphilus, associated with citrus wilt. Across the four genomes, the analysis identified 18,933 gene families, of which 7,417 are shared by all species. Phylogenetic reconstruction and genome collinearity analysis both confirmed that P. biglobosus is most closely related to P. lingam, consistent with the two fungi sharing a canola-relevant host range while differing in disease presentation.

Comparing carbohydrate-active enzyme complements across the four species, the authors propose that these pathogens breach plant mechanical barriers through the synergistic action of pectin degradation and lignocellulose decomposition. The comparative data suggest this coordinated enzymatic strategy is a shared feature of the genus rather than a peculiarity of the canola pathogen alone, although the proposal rests on sequence-based comparison rather than direct enzyme assays.

Transporter biology also differed among the four species. P. tracheiphilus exhibited the highest number of DHA1-family transporters, while P. lindquistii carried a large complement of DHA2-family transporters. The study reports these copy-number differences as observations, and the authors do not present experimental evidence linking the counts to specific host adaptations.

Perhaps the most striking divergence emerged in core secondary metabolism genes. In P. biglobosus, these genes encode products such as clavulanic acid and choline, among others, which the authors suggest may facilitate host infection. In contrast, the corresponding genes in P. lingam and P. lindquistii encode acrylamide toxins. The authors interpret this difference in encoded metabolite classes as a likely contributor to host specificity among Plenodomus species, potentially helping explain why closely related fungi target different crops, while noting that this interpretation is based on gene annotation rather than functional characterization.

By combining a long-read assembly of P. biglobosus with a four-way comparative analysis, the study delivers a comprehensive catalog of the fungus’s genome and a set of candidate virulence factors and effectors shared with or distinct from its relatives. The authors note that these components play an essential role in pathogen-plant interactions and that their findings provide valuable insights into the infection strategies and pathogenic mechanisms of blackleg pathogens.

As with any genome-led study, the identified genes remain candidates until functional experiments confirm their roles, but the assembly and comparative framework now give researchers a concrete starting point for dissecting how a single fungal species and its close relatives deploy cell-wall-degrading enzymes, transporters, and secondary metabolites against their respective hosts.

Subject of Research: Whole-genome sequencing and comparative genomics of the blackleg pathogen Plenodomus biglobosus

Article Title: Whole-genome sequencing and comparative genomic analysis of Plenodomus biglobosus

Article References: Ma, X., Shi, Z., Huo, H., Guo, C., Yang, Y., Huangfu, J., Fan, Y., Zhang, Y., Li, Z., & Huangfu, H. (2026). Whole-genome sequencing and comparative genomic analysis of Plenodomus biglobosus. BMC Genomics. https://doi.org/10.1186/s12864-026-13368-5

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13368-5

Keywords: Plenodomus biglobosus, blackleg disease, whole-genome sequencing, comparative genomics, carbohydrate-active enzymes, canola, Brassica, plant pathology, virulence genes, secondary metabolism, PacBio sequencing, BMC Genomics