DELETION OF HCF-1, A HYDROPHOBIN GENE OF CLADOSPORIUM-FULVUM, DOES NOT AFFECT PATHOGENICITY IN TOMATO

Hydrophobins are ubiquitous proteins of fungal walls forming an outer layer on hyphae and conidia. Surface hydrophobins may play a role in t he establishment of biotrophy by masking the cell wall from detection and attack by the plant. This paper describes the effect of ablating t he hydrophobin gene HCS-I from Cladosporium fulvum, the causal agent o f tomato leaf mould. HCf-1-less mutants, obtained by gene replacement, showed no accumulation of HCf-1 mRNA and no production of HCf-1 prote in. The hydrophobicity of these isolates was reduced and the colonies displayed an ''easily wettable'' phenotype. When tomato plants were in oculated with the HCf-1-less mutant, the infection symptoms were not s ignificantly different from plants infected with wild-type C. fulvum. The extent of fungal biomass was determined by ELISA and showed no sig nificant difference when compared with the wild-type. These results sh ow that HCf-1 is not essential for pathogenicity in C.fulvum. (C) 1998 Academic Press.