GENETIC-TRANSFORMATION OF THE VASCULAR WILT FUNGUS VERTICILLIUM-DAHLIAE

To facilitate genetic analysis of pathogenicity of Verticillium dahlia e, a vascular wilt pathogen, a DNA-mediated transformation system has been developed. Resistance to hygromycin B was obtained by transformin g spheroplasts with the cosmid vector pAN7-2. Transformation efficienc ies ranged between 3 and 5 transformants/mu g vector DNA. The transfor ming DNA was integrated into the V. dahliae genome, in single and mult iple copies and in tandem array. In several multicopy transformants, m inor alterations in the integrated DNA sequences were evident followin g extensive vegetative growth in the absence of hygromycin B. Electrop horetic karyotype analysis also provided direct evidence of chromosome rearrangements in two transformants. The availability of a transforma tion system for V. dahliae will facilitate the cloning and characteriz ation of genes that are important for pathogenicity and development.