SEQUENCE-TAGGED SITES (STS) FOR STUDIES OF MOLECULAR EPIDEMIOLOGY OF SCLERODERRIS CANKER OF CONIFERS

Scleroderris canker is a very damaging disease of conifers caused by a fungal pathogen, Gremmeniella abietina var 'abietina'. This fungal pa thogen is now known to comprise a number of distinct races and biotype s. In North America, two races, an indigenous North American race and an introduced European race, are present. In Europe, three distinct bi otypes have been reported within the European race: one in the Alps, a nother in Fennoscandia, and a third that overlaps with the first two. We used random amplified microsatellites (RAMS) and DNA sequencing wit h arbitrary primer pairs (SWAPP) to design five PCR primer pairs flank ing polymorphic regions of the genome of the European race of G. abiet ina. Length polymorphisms produced by repeats of basic units in micros atellites were distinguished by electrophoresis of PCR products in aga rose gels, and point mutations were identified by low-ionic-strength s ingle-strand conformation polymorphisms (LIS-SSCP). Some primers gener ated private alleles in the European biotype and the psychrophilic Alp ine and Fennoscandian biotypes, i.e., alleles that were fixed within t he two groups but polymorphic between them. Conversely, one pair of pr imers amplified at least 3, 4, and 7 alleles in the Fennoscandian, Alp ine, and European biotypes, respectively. The Alpine and Fennoscandian biotypes, although geographically separated, were genetically more cl osely related to one another than to European biotype, which has an ov erlapping distribution. However, both Alpine and Fennoscandian biotype s have similar ecotypic adaptation. The evolution of these biotypes co uld be explained by their geographic separation following the end of t he last glaciation.