RAPD-based Molecular Diagnosis of Mixed Fungal Infections on Oilseed Rape (Brassica napus): Evidence for Genus- and Species-specific Sequences in the Fungal Genomes

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 gtnus Allernaria, and 15 RAPD markers were highly specific for distinct fungal species. This report demonstrates the value of the RAPDPCR technique to amplify taxon-specific DNA fragments that can be used as hybridization probes for the diagnosis of a variety of rape seed pathogens (Aiternaria hrassieae, A. brassieicola, A. raphant, Cylindrosporium concentrieum; Fusarium moniliforme; Phoma lingam; Pythium sp.; Rhizoetonia solani: Selerotinia sclerotiorum, Verticillium dahliae, V. latericium).