Transformation of Fusarium culmorum with the β-D-glucuronidase (GUS) reporter gene:: a system for studying host-pathogen relationships and disease control

The small grain cereal pathogen Fusarium culmorum was successfully transformed with the Escherichia coli beta-D-glucuronidase gene (gusA) (GUS reporter gene) using the E. coli hygromycin phosphotransferase gene (hph) as a selectable marker. The frequency of transformation to hygromycin B tolerance was higher for plasmid pGUS5 than plasmid pTUBA-GUS. Southern hybridization analysis of transformants revealed that single or multiple copies of the gusA gene were integrated into the genomes of transformants. Following successive sub-culturing on nonselective media, the majority of transformants remained tolerant to hygromycin B. After mitotic stabilization by single conidial isolation, most transformants retained GUS expression, although individual transformants differed markedly in GUS activity levels. Transformants were not found to differ in pathogenicity towards wheat seedlings, as compared to the wild type progenitor isolate. Expression of gusA during fungal growth on plants was detected both macroscopically and microscopically. The Feasibility of using a F. culmorum GUS transformant as a screening tool For evaluating fungicide efficacy was examined, and results showed that the GUS reporter gene system allowed discrimination between the effectiveness of different fungicides against F. culmorum foot rot of wheat. (C) 1998 Academic Press.