Differentiating characteristics between Melampsoridium rusts infecting birch and alder leaves

Melampsoridium rust epidemics on alder occurred in Estonia in 1996-1998, an d in Finland in 1997-1998. In this study we show that the length and roundn ess of urediniospores and the PCR-amplified internal transcribed spacer (IT S) sequences of rusts occurring on Alnus and Betula are different. Morpholo gically the rust on alder belongs to M. hiratsukanum, and based on our resu lts is not conspecific with M. betulinum. The sequence comparisons indicate d that 5.8S rDNA was similar in both Melampsoridium species and identical t o several Cronartium sequences. The 5.8S rDNA. of Melampsoridium was also m ore similar to Pucciniastrum, Chrysomyxa and Puccinia than to Melampsora sp ecies. The ITS sequences were distinct from all other rusts, but relatively similar to Cronartium, Pucciniastrum and Chrysomyxa sequences.