Development of a Fluorescently Tagged <i>Fusarium oxysporum</i> f. sp. <i>lini</i> Strain Using Advanced Genetic Labeling and Its Pathogenicity Assessment

Research on Fusarium oxysporum f. sp. lini (Foln), a fungal pathogen of Linum usitatissimum L. (flax) responsible for significant crop losses, requires effective methods for visualizing fungus–plant interactions to improve understanding of this pathosystem. In this study, transgenic Foln strains expressing GFP or dsRed fluorescent markers were generated via Agrobacterium ‐mediated transformation. Several Agrobacterium tumefaciens strains were tested, and those with the highest transformation efficiency were selected. Transformants were screened based on phenotypic characteristics and further validated using molecular biology techniques. Since transgenesis can influence a fungus′s ability to infect its host, the pathogenicity of the generated Foln lines was assessed by measuring the expression levels of pathogenesis‐related genes and ROS metabolism‐related genes, alongside quantifying O 2 − and H 2 O 2 levels in the infected plant tissue. The presence of dsRed and GFP fluorescent markers was confirmed using fluorescence microscopy. Ultimately, two transformants exhibiting pathogenic characteristics similar to the wild‐type Foln strain were selected. These transformants represent valuable tools for further studies of Foln pathogenesis in flax. Additionally, the workflow developed here can be adapted to generate fluorescent transformants of other F. oxysporum pathogenic strains.