Transformation of the fungal pathogen Cryphonectria parasitica with a variety of heterologous plasmids

Summary An efficient DNA-mediated transformation system for the pathogen of chestnut, Cryphonectria parasitica, is reported. Ten vectors, each containing a promoter from Cochliobolus heterostrophus, Aspergillus nidulans, Ustilago maydis, Cephalosporium acremonium, Neurospora crassa or cauliflower mosaic virus, were creened for their ability to confer resistance to hygromycin B, benomyl or G418 sulfate. Transformants were obtained with all vectors screened and, in each case, transformation occurred by integration of the foreign DNA into the host genome. The initial transformation efficiency ranged from approximately 1–60 transformants/g circular DNA. Under optimized transformation conditions, the transformation rate of the vector pDH25, which contains the trpC promoter and terminator of A. nidulans, exceeded 10⁵ transformants/g DNA. The ease with which C. parasitica is transformed should greatly facilitate the genetic manipulation of this fungal plant pathogen.