RAPD-BASED MOLECULAR DIAGNOSIS OF MIXED FUNGAL-INFECTIONS ON OILSEED RAPE (BRASSICA-NAPUS) - EVIDENCE FOR GENUS-SPECIFIC AND SPECIES-SPECIFIC SEQUENCES IN THE FUNGAL GENOMES

Oilseed rape (Brassica napus) is attacked by many parasitic fungi whic h often occur in mixed infections. Monitoring of these phytopathogens by morphological criteria is restricted due to their appearance especi ally in the later stages of disease development. We have developed mol ecular markers for a clear-cut differentiation of a variety of rape se ed pathogenic fungi based on randomly amplified polymorphic DNA (RAPD) . Twenty polymorphic fragments have been selected in Southern hybridiz ation experiments to test their taxon-specificity. In summary, only fo ur amplification products gave unspecific cross-hybridization patterns , one fragment corresponds to a genetic element common to three specie s within the genus Alternaria, and 15 RAPD markers were highly specifi c for distinct fungal species. This report demonstrates the value of t he RAPD-PCR technique to amplify taxon-specific DNA fragments that can be used as hybridization probes for the diagnosis of a variety of rap e seed pathogens (Alternaria brassicae, A. brassicicola, A. raphani; C ylindrosporium concentricum; Fusarium moniliforme; Phoma lingam; Pythi um sp.; Rhizoctonia solani; Sclerotinia sclerotiorum; Verticillium dah liae, V. latericium).