DETECTION OF GENETIC-VARIATION BETWEEN OPHIOSTOMA-ULMI AND THE NAN AND EAN RACES OF O-NOVO-ULMI IN SWITZERLAND USING RAPD MARKERS

The structure of the Ophiostoma ulmi and Ophiostoma novo-ulmi populati on of Switzerland was analysed. 79 Swiss isolates were compared to ref erence strains from various countries. A dendrogram from RAPD profiles was produced. O. ulmi and O. novo-ulmi were clearly separated into tw o major clusters. O. novo-ulmi was further divided into the EAN and NA N races. This classification is consistent with subgroups by taxonomic parameters (growth rate, culture aspect, fertility barriers). The var iation detected within the EAN and NAN races indicates a post-epidemic situation In Switzerland. A clonal population is present only in a re stricted area in mid-eastern Switzerland, indicating a still active di sease front.