LACK OF ASSOCIATION BETWEEN CERATO-ULMIN PRODUCTION AND VIRULENCE IN OPHIOSTOMA-NOVO-ULMI

Cerato-ulmin (CU), a hydrophobin produced by Ophiostoma novo-ulmi, has been implicated in the pathogenicity of this fungus on elm. We have g enerated a CU- mutant by transformation-mediated gene disruption of a highly virulent (aggressive) strain of O. novo-ulmi. The inability of the mutant to synthesize CU was confirmed by transcript analysis as we ll as turbidity and immunological measurements. Bioassay of the CU- st rain in highly susceptible elm trees indicated no difference in the vi rulence parameters, percent vascular discoloration, and percent foliar wilting, when compared with the wild type. Our results indicate that the inability to produce CU had no measurable effect on the ability of O. novo-ulmi to produce symptoms of Dutch elm disease on inoculated e lms.