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An important substance in the signalling between individuals of Mucor-like fungi is trisporic acid (TA). This compound, together with some of its precursors, serves as a pheromone in mating between (+)- and (2)-mating types. Moreover, intermediates of the TA pathway are exchanged between the two mating partners. Based on differential equations, mathematical models of the synthesis pathways of TA in the two mating types of an idealised Mucor-fungus are here presented. These models include the positive feedback of TA on its own synthesis. The authors compare three sub-models in view of bistability, robustness and the reversibility of transitions. The proposed modelling study showed that, in a system where intermediates are exchanged, a reversible transition between the two stable steady states occurs, whereas an exchange of the end product leads to an irreversible transition. The reversible transition is physiologically favoured, because the highproduction state of TA must come to an end eventually. Moreover, the exchange of intermediates and TA is compared with the 3-way handshake widely used by computers linked in a network. [ABSTRACT FROM AUTHOR]

Examines the specificity of polymerase chain reaction primers to the rape seed pathogen Leptosphaeria maculans. Differentiation of DNA bands between isolates; Determination of group-specificity pathogenicity; Use of chemical and dideoxynucleotide chain termination methods.

Oilseed rape (Brassica napus) is attacked by many parasitic fungi which often occur in mixed infections. Monitoring of these phytopathogens by morphological criteria is restricted due to their appearance especially in the later stages of disease development. We have developed molecular markers for a clear-cut differentiation of a variety of rape seed pathogenic fungi based on randomly amplified polymorphic DNA (RAPD). Twenty polymorphic fragments have been selected in Southern hybridization experiments to test their taxon-specificity. in summary, only four amplification products gave unspecific cross-hybridization patterns, one fragment corresponds to a genetic element common to three species within the genus Alternaria, and 15 RAPD markers were highly specific for distinct fungal species. This report demonstrates the value of the RAPD-PCR technique to amplify taxon-specific DNA fragments that can be used as hybridization probes for the diagnosis of a variety of rape seed pathogens (Alternaria brassicae, A. brassicicola, A. raphani; Cylindrosporium concentricum; Fusarium moniliforme; Phoma ligam; Phythium sp.; Rhizoctonia solani; Sclerotinia sclerotiorum; Verticillium dahliae, V. latericium) [ABSTRACT FROM AUTHOR]

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