Molecular Plant Pathology – Pathogen Profiles

Cladosporium fulvum (syn. Passalora fulva), a highly specialized plant pathogen as a model for functional studies on plant pathogenic Mycosphaerellaceae


1 Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands
2 Centraalbureau voor Schimmelcultures, PO Box 85167, 3508 AD Utrecht, The Netherlands

Taxonomy:  Cladosporium fulvum is an asexual fungus for which no sexual stage is currently known. Molecular data, however, support C. fulvum as a member of the Mycosphaerellaceae, clustering with other taxa having Mycosphaerellateleomorphs. C. fulvum has recently been placed in the anamorph genus Passaloraas P. fulva. Its taxonomic disposition is supported by its DNA phylogeny, as well as the distinct scars on its conidial hila, which are typical of Passalora, and unlike Cladosporium s.s., which has teleomorphs that reside in Davidiella, and not Mycosphaerella.

Host range and disease symptoms:The presently known sole host of C. fulvum is tomato (members of the genusLycopersicon). C. fulvum is mainly a foliar pathogen. Disease symptoms are most obvious on the abaxial side of the leaf and include patches of white mould that turn brown upon sporulation. Due to stomatal clogging, curling of leaves and wilting can occur, leading to defoliation.

C. fulvum as a model pathogen: The interaction between C. fulvum and tomato is governed by a gene-for-gene relationship. A total of eight Avr and Ecp genes, and for four of these also the corresponding plant Cf genes, have been cloned. Obtaining conclusive evidence for gene-for-gene relationships is complicated by the poor availability of genetic tools for most Mycosphaerellaceae plant interactions. Newly developed tools, including Agrobacterium-mediated transformation and RNAi, added to the genome sequence of its host tomato, which will be available within a few years, render C. fulvumattractive as a model species for plant pathogenic Mycosphaerellaceae.

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(A) Adaxial side of a tomato leaf (MoneyMaker Cf-0) 18 days after inoculation with a compatible race of C. fulvum. Distinctive yellow spots can be seen as a result of dead palisade parenchyma cells. (B) Abaxial side of a tomato leaf (MoneyMaker Cf-0) 18 days after inoculation with a compatible race of C. fulvum. White mould can be seen developing into light brown patches where sporulation takes place.