Abstract Over the past half century a destructive blight of Cupressus spp., caused by Seiridium cardinale, has spread worldwide from North America, devastating forests, plantations, and ornamental cypresses. The epidemic has been particularly severe in the Mediterranean region, on C. sempervirens. Three species of Seiridium, S. cardinale, S. cupressi, and S. unicorne, are associated with cypress canker. To test the genetic variability of the Italian population of S. cardinale, a large sample of different isolates was analysed by RAPD (Random amplified polymorphic DNA) markers and compared with a number of other Seiridium spp. isolates from various hosts growing in different parts of the world. The results indicated a high level of homogeneity in the North-Italian population of the fungus, whereas certain variability was recognized in isolates from other hosts and other species. The isolates belonged to the North-Italian population appear to be very similar from the molecular comparison and in the same group was included also the isolate from Greece. The results are discussed in relation to the introduction and spread of the fungus in Europe
